The related theory and model tests of coal and gas outbursts in the face of hard coal roadway tunneling in the deep coal seam were studied to explore the coal and gas outburst mechanism of hard coal. Based on fracture mechanics, rock mechanics and theory of coal and gas outburst, a hypothesis of thin plate theory of coal roadway tunneling in the deep coal seam was proposed, and used to the model tests. The analysis results of thin plate theory of coal roadway tunneling in the deep coal seam show the size of working face, elastic modulus, the coefficient of lateral pressure and gas pressure have a great influence on coal and gas outbursts in the face of hard coal roadway tunneling in the deep coal seam. The results of model tests show that under the condition of large stress of surrounding rock and the consistence coefficient of coal, the critical conditions of coal and gas outbursts in the face of hard coal roadway tunneling in the deep coal seam are affected mainly by the surrounding rock stress, the elastic modulus, the coefficient of lateral pressure and the size of working face, and less affected by gas pressure. Under the condition of the large stress of surrounding rock, the large consistence coefficient of coal, the constant elastic modulus and the constant coefficient of lateral pressure, the critical axial stress of the model tests decreases approximate linearly with the increases of the working face size. The results of the model tests basically conform to the thin plate theory of coal roadway tunneling in the deep coal seam, which verify the hypothesis of thin plate theory of coal roadway tunneling in the deep coal seam.

In the traditional plastic potential theory, there is an implied assumption that the directions of principal stress and principal plastic strain increment are coaxial. However, there are non-coaxial phenomena during the rotation of principal stress axis and the traditional plastic potential theory can not describe this phenomenon reasonably. A quasi-elastic-plastic constitutive model was proposed based on the generalized potential theory, in which the traditional plastic strain increment was decomposed into quasi-elastic part and pure-plastic part. The quasi-elastic part obeys elastic rule and the pure-plastic part obeys the traditional plasticity theory. The proposed model is reasonable and convenient; and it can also reflect the non-coaxiality of soil. The validation results of simple shear test show that the simulation effect of the quasi-elastic-plastic model is good. The directions of the principal stress and the principal plastic strain increment simulated by traditional elasto-plastic model (coaxial model) are coaxial; while the simulation results of quasi-elastic-plastic model (non-coaxial model) can reflect the non-coaxiality during the rotation of principal stress axis. It proves that the quasi-elastic-plastic model based on the generalized potential theory conforms to reality better than the traditional elasto-plastic model (coaxial model) and it gives an effective method to study the non-coaxiality of soil.

It is a feasible method to study the deformation and failure of anti-dip layered rock slopes by using limit equilibrium method based on cantilever beam theory, which not only pay attention to deformation process, but also focus on the mechanics analysis. Based on the research status at home and abroad, this paper launched the research of cantilever beam limit equilibrium analysis model. Firstly, the concept of "reference surface" was raised through field phenomenon observation, by which the deformation geometric space conditions of the anti-dip layered slope can be partitioned; therefore the mechanism analysis of rock layer failure pattern could be done according to the different situations of partitions; and the conclusion was made that the formation mechanism of the failure surface is the combined effect of both curved tension and compression shear. On this basis, the hypothesis or the theoretical analysis of the various parameters in the cantilever beam limit equilibrium analysis model was given; and the calculation model was established. Finally, taking Zhongliang reservoir Xiaodongcao-Zhengjiadagou segment anti-dip bank slope in Wuxi County, Chongqing for example, based on the recognition of slope deformation and failure pattern, the theory of cantilever beam limit equilibrium model was used in this example, and the rationality of the model was verified. At the same time, the calculation steps were given; and the correctness of the analytical model was verified by numerical simulation method. Model results show that the damage zone can be divided into slip area, toppling area and toppling influenced zone; damage zone size is determined by slope angle, strata inclination and slope height; and damage zone only exists when the three relations (formula (13)) is greater than zero that deformation and failure could occur. The research results have theoretical significance and application value to the stability evaluation and prevention of anti-dip layered rock slopes.

The jointed rock mass is a discontinuous body with special structure, and shows the anisotropic mechanical characteristic. In order to understand its complex mechanical characteristic, the mechanical effects of single joint surface is analyzed theoretically; and the triaxial compression test is conducted on samples with single prefabricated joint. The test results show that the mechanical characteristic of jointed samples is governed by either joint surface or rock. Compared with the intact samples, the mechanical parameters of jointed samples reduce inordinately. The Young’s modulus, compressive strength, cohesion are in U-shaped along with joint inclination and the minimum value occured at the inclination of 60° jointed samples. On the contrary, the internal friction angle increases linearly with the joint inclination. With the increasing of confining pressure, the ratio of maximum to minimum of Young’s modulus and compressive strength decrease; it shows that differences of mechanical characteristic of various inclination jointed samples lessen.

For Ⅲ, Ⅳ grade rocks, the different deformation types of tunnel surrounding rocks are analyzed and forecasted using the elasto-viscoplastic finite element method based on Jiangxi highway tunnel. First, the Ⅲ, Ⅳ grade rocks are selected, to carry out indoor shear rheological tests and analyze generalized Kelvin rheological test curve and find the flow curves agree well with the model for Ⅲ, Ⅳ grades rock samples. Based on the generalized Kelvin model, viscoelastic model is derived under the stress - strain relationship of complex stress state. Finally, the dynamic viscoelastic back analysis method of the construction process is used to calculate rock parameters, combined with inversion parameters for prediction analysis of tunnel surrounding rock deformation. The research results are applied to the actual tunnel construction to guide and revise design and construction parameters, so as to provide a reasonable basis for safe construction.

Based on conformal mapping method of plane elasticity complex function, the analytical solution for non-circular supported tunnel subjected to in-situ stress can be obtained. According to the boundary conditions along the inner boundary of liner and the stress and displacement continuity conditions along the liner-surrounding rock mass interface, the basic equations for solving the analytic functions of the surrounding rock and liner are given. And the stresses and displacements are calculated. In the solving process, support delay and pure bond are taken into consideration. Taking the horseshoe tunnel for example, the tangential stresses of the rock excavation boundary and the contact stresses on the liner-surrounding rock mass interfaces are obtained. The results are compared with that by the ANSYS software. The numerical example shows that the results of two methods are in good agreement.

In order to reasonably determine the weights of index in the evaluation of the possibility and classification of rockburst, a combination weight method is proposed. Based on the theory of information entropy, the original formula is modified. Compared with the original formula, the modified formula is suitable under any conditions, which is more reasonable in theory. Then, Euclidean distance function is introduced to make the difference between the subjective and objective weight same as the difference between the favorable coefficients; and then the combination weight can be calculated. On the basis, the evaluation indexes are chosen in the analysis according to the causes of rockburst and its characteristics. Combining with the optimized grey clustering method, a grey evaluation model based on combination weight (GEM-CW) for predicting of rockburst proneness is established. Based on some deep rock projects at home and abroad, the GEM-CW model is adopted to predict the possibility and classification of rockburst. Compared with the fuzzy synthetic evaluation method, the attribute synthetic evaluation method, the unascertained measurement model and the matter-elements method, the prediction results of the GEM-CW model in the paper are close to the practical records, so as to prove that the proposed model is effective and available. Therefore, the proposed method provides a practical way to accurately predict the possibility and classification of rockburst in deep underground engineering.

X In order to study the influence of dry density, water content and soluble salt content on the thermal deterioration of earthen monuments, Hot Disk heat constant analyzer is used to test the thermal parameters of soils from different earthen monument sites such as Liangzhu, Tunguska Brazil and Jiaohe. Meanwhile, Tunguska Brazil soil is concentrated with different concentrations of NaCl, then the thermal conductivity coefficient is measured to analyze the influence of salt content. The results show that the thermal conductivity coefficients of three types of soils increase linearly with increasing water content and dry density. The thermal diffusion coefficient and specific heat volume are also increased with increasing water content and dry density. The thermal parameters of earthen monuments soils are found to be correlated positively to the SiO2 content in soil. For the above-mentioned three sites soils, their thermal parameters are different under same conditions; the Liangzhu soil is the greatest; Tunguska Brazil soil is second and Jiaohe is the least. In addition, concentrated NaCl increases the thermal conductivity of soil.

In light of that the, studies of mechanical response of rock under cyclic loading need to be more perfected, taking Yichang sandstone as the research object and using the geotechnical testing system RMT-150C for the test platform, the research on the prediction model of deformation rate in triangular wave unloading segment with the magnitude of ms., is carried out. Unloading process is divided into non-lag and lag time segment; and the required parameters and discrimination basis for each segment is given. Effect of lag time segment is pointed out quantitatively; and the prediction mode in time lag segment is also given. Then the concept of the apparent modulus of elasticity in the lag non-lag time segment is proposed; analysis of the test data shows linear relationship between the apparent elastic modulus of the rock sample before the sample was damaged under loading. On this basis, a prediction model of deformation rate by triangular wave unloading in non-lag time segment is established. As the test platform can not be accurately input triangular wave, after the average loading rate and loading rate is corrected by adding corrected constant term, the predicted deformation rate and stress-strain curves of the model are coincide precisely with the measured values, so as to indicate the rationality of the model.

Dynamic response characteristics including pore water pressure, axial strain of marine soft soil under impact loading are studied through triaxial test. Bound water content of saturated soft clay is obtained by thermal gravimetric analysis and theoretical calculation method before and after triaxial experiments. Research shows that water content ranged from 15.6% to 23.5%, bound water content ranged from 17.6% to 29.4%, volume coefficient is 2.1%-9.5% before and after under impact loading. Drainage consolidation of saturated soft clay is obvious, variation of bound water content is large before and after under impact loading. The law of dynamic discharge water of marine soft soil is different from law of static discharge water. The results reveal that main factors are initial water content, bound water content, void ratio, state of soil and loading mode. Finally, the law of dynamic discharge water of marine soft soil and its inspiration is summarized. The study results can provide reference for engineering design of soft soil foundation treatment.

Based on the sandstone’s high geostress area from where a high slope in Jinping, a series of pre-peak unloading tests have been carried out; and the complete stress-strain curve, deformation characteristics and degradation effect of deformation parameters are studied. The test results show that compared to loading failure, the rock’s brittle characteristics of unloading failure is obvious; and unloading failure needs lower deviatoric stress under the same initial confining pressure. The lateral strain and volumetric strain increase sharply in the process of unloading; and the expansion characteristics in the unloading direction is obvious. When the initial confining pressure is less than a value(30 MPa), the rock’s failure unloading percentage would increase along with initial confining pressure’s enlargement. But when initial confining pressure grow up to a value(40 MPa), the brittle characteristics is very obvious; and a few unloading percentage can cause the rock failure. Taking unloading percentage H which expresses unloading level as variable quantity, and making fitting of deformation parameters when in high and low stress. We get the functions between deformation degradation parameters and unloading percentage under unloading process. The test results and calculation method could benefit excavation for the stability analysis of slope under high geostress.

For the same deep mudstone, three testing methods of permeability (conventional testing method, variable confining pressure method, and pulse method under triaxial compression) have been conducted respectively. According to the testing results, large difference of permeability was found inbetween the three methods, in which the permeability of conventional method is 3-5 orders higher than those of the other two methods. The results of variable confining pressures method while its confining pressure exceeds about 5 MPa approach relatively the results of pulse method under triaxial compression. Permeability of pulse method slowly decreased with the increasing of deviatoric pressure, and dilatancy didn’t occur even when confining pressure reached 30 MPa. The results indicate that the permeability of mudstone is strongly sensitive to pressure; the intrinsic reason of which is that the cracks, fissures and pores in rock matrix tend to be compacted under high compression, which results in the reduction of pore size and connectivity for percolation channels and then causes the permeability to decrease; moreover, samples production, oven drying treatment, etc. also influence some of the permeability. Based on the results and the in-situ stresses conditions of mudstone, it is proposed that the variable confining method is suitable for the permeability and its development of reservoirs’ cap rock, while the results of pulse method under triaxial compression is more suitable for the cap rock of energy storage caverns and rock wall of wastes disposals. However, one should be very cautious while uses the results from conventional method. The research carried out supplies some constructive references for the analysis of the percolation properties and sealability of mudstone in deep strata.

The tests arrangements are systematically introduced firstly, including test facilities, similar ratios, modelling materials, model cases and so on. Then, the test results including accelerations of surrounding rock and tunnel structure, laws of strains and deformations of structures, failure features of upward slope. The analysis results show that: an amplified effect of acceleration and displacements of tunnel structures exist at the area which is of some distance from the entrance of the tunnel. There is not much differences in the law of the amplification effect for different gradients of upward slope. The amplification effect decreases as the gradient of upward slope increases. The analysis of the strain show that the tunnel structure is mainly subjected to transverse stress. A cycling load of tension and pressure acts on the cross-section of the tunnel which result in additional seismic bending moment on arch waist and arch feet, which could be seen as weak parts in seismic design of lining structure. The mechanical characteristics of lining has no relation with the gradient of upward slope. The additional moment is proportional to soil thickness and the inertia force of lining. As the gradient of upward slope increases, the soil-structure interaction effect is gradually weakened; and the failure modes of the slope are different, which include local slope collapse, large slump at the top of the lining, highstand sliding. Both of them are all the surface failure. But the tunnel openings are usually partially or completely buried, which severely affect the normal use of tunnel. Tests results provide references for seismic design of tunnel portal section in mountain tunnels.

Biaxial compression tests for granite in the underground caverns of Huangdao State Oil Reserves were virtually simulated using the bonded particle model (BPM) in particle flow code (PFC2D). The mesomechanical parameters corresponding to the macromechanical parameters of indoor compression tests were obtained through trial and error method. The simulated elastic modulus and Poisson's ratio show good agreement with the corresponding values of indoor compression tests. Due to the circle particle in BPM, cohesion and internal friction angle have some certain deviation compared with those of indoor compression tests. The simulated failure pattern of specimens is shear failure along single inclined plane, which agrees with the failure pattern of indoor compression tests. With the calibrated mesomechanical parameters, the microcrack development and energy dissipation of granite were further studied. The results show that there are three main stages during the microcrack development, i.e. stable development stage, rapid increase stage and stable development stage. The changing of boundary energy, strain energy, bond energy, frictional energy and kinetic energy has given an excellent explanation of the mesoscopic mechanics.

The analysis of changing rule of shear strength indexes of soft soil with consolidation degree under the effect of surcharge load is executed based on the theoretical derivation and indoor tests; since the conventional shear strength indexes cohesion value and internal friction angle cannot represent the mechanical character of the soft soil at any consolidation degree at the effect of the surcharge load accurately, and the existed limit equilibrium method considering the increasing of the shear strength value with the consolidation degree cannot get the data such as stress field, displacement field that are needed by the practical engineering. The comparison analysis has been done for two existed formulae, and deduced that they have equivalence property. From the viewpoint of pore water pressure, a new formula is presented; and from which we get: the internal friction angle at any consolidation degree increases with the consolidation degree monotonously; and the cohesion value decreases with the consolidation degree monotonously; when the consolidation degree is fixed and is not 100%, the cohesion value presents the linear increasing relationship with the initial consolidation pressure; but the value of the internal friction angle is not related to it. The indoor test shows that, the newly deduced formula results fit better with the test results than the existed formulae results; since the total stress parameters and the effective stress parameters have been considered comprehensively, so as to prove the validity and advantage of the newly deduced formula.

The interaction mechanism of geosynthetics-soil interface is complicated and also important for designing the geosynthetics reinforced structure. A series of large scale direct shear tests, using Fujian standard sand and Fiberglass geogrid, are used to investigate the influence of longitudinal and transverse ribs and aperture pattern on the interface shear behavior of soil against geosynthetics. The test results show that both the longitudinal and transverse ribs play an important role in improving the interface strength through different courses of action. The shear force of interface will be shared by passive resistance of transverse ribs and friction resistance of longitudinal ribs when shear displacement is small; while the longitudinal ribs present the role of framework to improve the geogrid stiffness with the increasing of transverse resistance due to the shear displacement increasing. Therefore, coordinate work of longitudinal and transverse ribs will help to advance the interface shear strength.

The soil water retention curve (SWRC) tests under the three different temperatures are carried out. The volume shrinkage deformations also are measured at the same time to amendment miscount caused by volume change. The test result shows that the shrinkage is obvious in the drying process, the void ratio reduced to 0.645 from 0.675, but the difference of final void ratio under different temperatures is only 0.003; it is shown that the silt’s deformation is not sensitive to temperature. The water holding capacity is significant different under the action of different temperatures. The air-entry value is smaller when the temperature increased. The difference of water holding capacity reach maximum under the action of suction of 50 kPa. The water content is 0.397, 0.361 and 0.338 respectively under the temperatures of 20 ℃, 30 ℃, 40 ℃; but the difference is decreasing with the suction increased. The water physical properties, water and gas’s occurrence are changed under the different temperatures and it lead to the changing of the water holding capacity.

Landslide-debris avalanches always cause disastrous catastrophes because their high speed and long runout. Their complex movement mechanisms make the prediction of runout very difficult. Laboratory experiments are used to investigate some factors influencing the movement of rock fragments, including size of fragments, bed roughness and scrap. Flume tests show that the runout of rock fragments is decided by front part and increased with the increasing size of rock fragments. The runout becomes smaller when the bed roughness increasing or scrap is added. The movement mechanism of landslide-debris avalanche is also discussed based the physical properties of granular material and previous studies: the force between particles is much smaller than intact rock in high speed, so the “cohesion” of particles can not ensure the landslide maintain an fixed shape, and the friction reduces when transferred by the particles at bottom, making the result of long run out.

Three common empirical estimate-methods of reservoir bank landslide surge are introduced. They are American Society of Civil Engineers recommended method, PAN Jia-zheng method and IWHR empirical formula method. For the landslide surge prediction of Egongdai ancient landslide in Lechangxia Reservoir, three common empirical estimate-methods were adopted and a physical model with geometric scale of 1:150 is constructed. Surge generated by different sliding velocity are calculated and tested under the design flood level and normal water conditions. By comparing the results of surge height of hillside on the opposite bank of the point of water entry of landslide, dam location and B3 measuring point, it is shown that the calculation results of three common empirical estimate-methods are quite different; and the results of Pan Jia-zheng method agree with the test results best. Through the further analysis of the differences between calculated results of three common empirical estimate-methods, PAN Jia-zheng method is recommended when using the empirical estimate-methods to predict reservoir bank landslide surge. In addition, some phenomena appeared in the physical model test are also explained. The method recommended can be available for landslide surge prediction.

Talking the strong expansive soil of Guangxi as research object. 30 days evaporation experiment was respectively carried out for expansive soil with on without vegetation cover and under plastic sheeting cover, to explore the influence of continuous evaporation process on moisture-heat behavior and fissures development. The results show that without vegetation cover, the surface soil amount and rate of volumetric water content changes respectively are 7.38% and 0.17%/d; with vegetation cover, which are respectively 5.29% and 0.07%/d; apparently under vegetation cover, whose dehydration content and drying rate were less than that of without vegetation cover. For plastic sheeting cover, expansive soil evaporation is curbed and no water loss. Without no vegetation and plastic sheeting cover, the average temperature changes of expansive soil are 7.36 ℃，9.72 ℃ respectively, which is 5-8 ℃ higher than that with vegetation cover 2.03℃; obviously, the vegetation cover reduces expansive soil temperature variation. Without vegetation cover, expansive soil fissure depth is up to 32 cm, which is closer to 28 cm influence depth of moisture-heat. Under vegetation and plastic sheeting cover, no apparent fissure carried out in the plane and vertical; vegetation cover and the state of evaporation curbed can prevent expansive soil fissure developing.

Now，the soil between the piles is usually considered to be elastic in many calculation models of portal double-row anti-slide piles. Because of the soil being the elastoplastic material, the results of elastic models are not consistent with the reality. A new plane link finite element model is established. The soil between the piles is considered to be the elastoplastic in this model which combined the linear elastic model and the plastic model. A calculation method for calculating internal force of the fore-pile and the rear-pile is developed, which is based on structural mechanics, soil constitutive relationship and numerical method. First, the soil total stress between the piles is acquired by calculation based on the displacement of pile top used in the displacement method. Then the internal force of portal double-row anti-slide piles is calculated by numerical method, linear elastic elements and plastic elements of this numerical method, whose basic parameters are derived according to the Lade-Duncan constitutive model. Last, combining with engineering example, the internal force of portal double-row anti-slide piles is calculated with the finite element program ANSYS. Compared with the monitoring data and the calculating results of elastic model, the calculating results of elastoplastic model are more consistent with the monitoring values.

Based on the theory of slip line field, this paper proposes a limit curve method of slope stability according to the deformation situation; the method is the inverse process for computing a heavy slope ultimate load and the dual process of strength reduction method. Defines two evaluation indexes: the degree of safety(DOS) and the degree of failure(DOF) according to the deformation failure criterion of the limit stable slope curve and the slope surface intersection computed by characteristic line difference method(SCM) and the slope limit experimental approximate formula(CCM). The method does not require assuming and searching critical slip surface. Classic examples and typical examples show that with the increase of nodes, the accuracy of SCM increases; when boundary step is constant, the judgment value obtained by three spline interpolation are unchanged, which proves the stability of SCM. Typical examples show that the larger the slope angle becomes, the lower the slope stability is; limit slope curve and slope is from without intersection to intersection, which proves that the correctness of the deformation failure criterion. Comparing the results from the two examples show that the safety factor is large and SCM, CCM results are comparable; this paper increases external load relative to the original boundary conditions; so the safety factor becomes smaller; SCM, CCM is conservative. To calculate the correct rate, this paper uses 34 samples: safety factor method is 67.7%, the stress state method is 73.5%, CCM is 79.4% and SCM is 70.6%, which indicates that SCM, CCM correct rate is higher. The conclusions of SCM, CCM factor sensitivity analysis and safety coefficient method are completely consistent. By analyzing and computing the slope stability and the ultimate slope angle of open pit mining, the report about SCM, CCM is the same as the original; when the parameter variable is smaller, CCM is more conducive to practice, which indicates that the method has a certain value in engineering applications.

This paper presents the study of interaction between the bottom built-in piles and landslide mass through the landslide physical model test. Based on the monitoring data from micro soil pressure cells and resistance strain gauges, mechanical characteristics of model pile, bending moment distribution rule of pile body and model deformation failure mode are studied. The test results show that the trust behind the pile is a parabolic distribution and the resultant force point is in half of free part above the sliding surface. Since the built-in piles take the most part of pushing force, the soil resistance in front of it is more stable and smaller. Meanwhile, the bending moment distribution form of pile body is different from any ordinary anti-sliding pile. The range from 0 to 15 cm depth is the main bearing area of bending moment and the maximum moment lays in one third of free part above the sliding surface. The bending moment near the sliding surface is relatively small. At last, the sliding mass flows above the model piles under the pushing force when the test comes to the end. The results of indoor model test show some regulations of the anti-sliding characteristics and provide scientific guidance for the design of rock-socketed piles.

Considering the limitation of the unified strength theory (UST) in nonlinear fitting and nonlinear features of geotechnical materials, a brittle-shear strength analysis method is proposed; and a transition bilinear formula is derived. Nonlinear strength feature of Hoek-Brown criterion is explained based on the double failure mechanism of fracture and shear; and an associated formula with highly correlation is obtained. Mine-by tunnel and the strength of Beishan granite data results analysis show that coefficients of correlation of Hoek-Brown rock mass strength, experimental data and brittle-shear strength values are all above 0.98. Twin formulas of Hoek-Brown criterion in the form of UST are derived based on the brittle-shear nonlinear fitting. Application of UST to fitting nonlinear strength of geotechnical materials is realized.

For the complex anti-inclined rock slope with many groups of fissures, considering the block and parent rock isn’t completely separated by fissures, a stability analysis method for it is proposed. At first, based on the rock layer’s bearing mode and contact relationship, a rock layer’s deflection calculation method is established. Then taking the rock layer’s deflection for relation variables, the calculation equations are built. Through solving the equations, the interlayer’s load can be obtained. So the loads on the rock block’s fissures are quantified; and accordingly a fracture mechanics model is established. Through fracture mechanics, rock block’s stability analysis method is established. At last, through a case study, it is shown that the results calculated by the proposed method agree well with the actual situations.

In order to investigate the effect of cracking orientation on the stability of tunnel surrounding rocks, experimental and numerical studies were implemented. In the experiment, cement mortar models with different cracking orientations were made and loaded after cured room temperature for 30 days. In the numerical simulation, the concrete damaged plasticity was adopted. The stresses at the points around the tunnel and the stress intensity factor of crack tips were calculated; the results were in good agreement with the experimental results. The results show that cracks in the spandrel can reduce the stability and strength of tunnels, and induce a great stress concentration at the crack tip and the sidewall of tunnels; but this phenomenon exist in differences due to the angle between cracks and sidewalls. When =60° and =130?, cracks produce the most serious effect on the stability and strength of tunnels; and the peak of damage stress are only 40.9% and 41.8% of that of tunnels without cracks.

The Jurassic sand-mudstone alternating stratum is one of typical sliding-prone layers in Three Gorges Reservoir region, where the landslides occur with high frequency. Due to this characteristic lithology combination and architectural feature, the stratum is one key area of landslide control in Three Gorges Reservoir region. In order to further study the stability of rock slope with soft-hard alternating layers, the paper presents a new calculation model of soft-hard interbedding rock slope by means of the analysis on an idealized model. Besides, a shear strength parameter degradation model of soft-hard interbedded rock slope is proposed with considering the effect of weathering for shear strength parameter degradation of the discontinuity plane and a space variation function. Moreover, function expression of shear strength parameter degradation is educed along surface of the layer. The function presented the relationship between weathering thickness and strength parameters, which was in favour of the quantitative analysis of slope stability. Then, utilizing this function weakened the shear strength parameters along surface, evaluating slope stability with the weakened parameters, obtaining the relation curve of stability coefficient and distance from the analyzed point to slope surface. Finally, it is proved that the shear strength parameter degradation of the discontinuity plane of soft-hard interbedded rock slope is significant to its stability assessment with slope case study in Three Gorges Reservoir region. It is concluded that the assumption that shear strength parameters remain constant distribution along layer surface has certain limitation in the stability analysis of single sliding surface slope. Moreover, if the degradation of shear strength parameters of structural planes is not under consideration, it may lead to the result of stability calculation unsafe.

Laminated soil distributes widely in the sea around China. Due to its special fabric, its physico-mechanical properties are different from the normal soil which will affect prediction of pile driving, spudcan penetration. In this paper, field piezocone penetration test(CPTU) and laboratory test methods are used to analyze the physico-mechanical properties of laminated soil in South China Sea; and the shear strength of laminated soil is discussed. The test results show that the physico-mechanical properties of laminated soil are different from normal sand’s or clay’s ones. Since the sand lamination presence, the undrained shear strength of laminated soil getting from UU tests is conservative; and it is the lower limit of that got from CPTU. The results of CPTU could show the special characteristics of laminated soil more clearly. The change scale of friction ratio of laminated soil got from CPTU is from 0 to 8 which is much larger than that of normal sand and clay. The relationship between friction ratio and corrected cone resistance could be simulated with hyperbola approximately. The special characteristics of laminated soil should be considered when the undrained shear strength is determined in static analysis properly.

During the exploitation of low permeability reservoir, the formation pressure depletes slowly and the effective stress to the rock grain increases. The effective stress may cause rock grain to deform, resulting in the primary or structural deformation; and this deformation makes the rock physical property parameters such as porosity and permeability become quite sensitive to effective stress. Therefore，it is necessary to know the function mechanism and property of stress sensitivity for low permeability reservoir. Based on the particle accumulation model, a capillary module, considering the arrangement of particles and the deformation of particles, has been established to express the stress sensitivity of capillary and porous media. The elastic deformation amount of the capillary has been calculated by Hertz contact deformation principle. And the quantitative characterization of stress sensitivity for capillary and porous media has been studied. The function mechanism on stress sensitivity of low permeability reservoirs is discussed by using the effective percentage of capillary and capillary deformation law. The research results show that the stress sensitivity for permeability is much more important than that for porosity in low permeability reservoirs. The effect of stress variation on porosity is small; but its influence on permeability is very large. The permeability stress sensitivity of three-grain contact deformed rock is greater than that of four-grain primary deformed rock. Compared with the primary deformed rock, the structural deformed rock has stronger permeability stress sensitivity. The stress sensitivity of low permeability reservoirs depends on some distinct factors such as the arrangement of particles, the deformation of particles, microscopic pore structure, solid-fluid interfacial force and threshold pressure gradient. The stronger the heterogeneity of low permeability reservoir is, the greater the stress sensitivity is; and thus the effect on oil production is larger. The quantitative module of stress sensitivity considering the effective percentage of capillary and the elastic deformation amount can explain the stress sensitivity of low permeability reservoirs based on the microscopic mechanism. These results offer a very important base and guide for researching and designing the production performance of the low permeability reservoir.

Radionuclides will transport to the biosphere after the overpack destroyed in the high-level radioactive waste(HLW) disposal repository. The hydraulic conductivity of buffer/backfill material plays an important role in evaluating the properties of the engineering barrier of HLW disposal repository. The permeability characteristics of Gaomiaozi bentonite-sand mixtures are studied by using the flexible wall permeameter and taking 2.0×10-5 mol/L Eu(III) solution as influent. The hydraulic conductivities are measured at K=(2.07-5.23)×10-10 cm/s. Test results show that there is no significant change in hydraulic conductivity of bentonite-sand mixtures, swelling with water, with the sand ratio ranging from 0% to 50%. Therefore, the requirement of low permeability for buffer/backfill material should be met by these mixtures. The effective clay dry density (ECDD) is used in this paper; and a good exponential relationship between volume swelling strain and ECDD and a linear-attenuation relationship between the logarithm value of hydraulic conductivity and ECDD of bentonite-sand mixtures are obtained. Compared with the distilled water, the hydraulic conductivities of bentonite-sand mixtures are smaller when influent is the 2.0×10-5 mol/L Eu(III) solution, which may result from the effect of influent viscosity.

The reinforcing and restraining effect of piles embedded in soils is objective existence. However, the correlative research work on pile groups settlement methods is not deep enough and needs to be continued. Based on the shear displacement method, considering the reinforcing and restraining effect, the settlements of the analyzing pile caused by loads on the pile top were calculated, including the reduction effect caused by the existence of the other adjacent piles. And the additional settlements of the adjacent piles arising from the settlement of the loaded pile were obtained as well. Thus a simplified formula of interaction coefficients between any two piles was presented. Meanwhile, the equivalent shear stiffness coefficients of soil around each pile were developed; and an equation of displacements caused by load on top of the analyzing pile imbedded in multi-layered soils was built; so recurrence relations of settlement and axial force of pile shaft between upper and lower of each pile sections were respectively deduced; in the process of deduction, Boussinesq solution was modified to include the effect of different embedded depths, and then used to derive the equivalent stiffness coefficients of the soil under the pile tips. Lastly, the formula was extended to the settlements calculation of high and low cap pile groups. Different methods were compared with two engineering cases. The results show that the load-settlement curve computed by present method agreed well with those measured from real engineering cases; and the calculating interaction coefficients are much less than ones calculated by the elastic theory method.

Pile’s bearing performance of building can be changed with time, because of the rheology of roch and soil. The time- dependent deformation of piles may affect the serviceability of piled structures after completion. This paper presents the results of a pile loading test under working load for a period up to 100 days. Two 800 mm-diameter bored piles with different pile lengths for bridge foundations were tested. The axial load distribution along the piles during loading was measured with stressometers attached to the reinforcements. The side friction resistance was obtained during each loading. The creep behavior and the settlement of the piles under serviceability limit states were revealed. The test results were analyzed using the new spatiotemporal effect theory of pile’s bearing performance. Analytical results were obtained with calibrated parameters. The results can be used for the design of pile foundation and to predict the long-term settlement of piles，and to solve the problem of controlling the differential settlements after bridge being completed.

The original Maksimovic peak shear strength criterion, has a concise form and clear physical meaning of the used parameters; but it cannot be used as a predictive tool to assess the peak shear strength of rock joints, because the roughness angle , which reflected the roughness of joint surface, is determined by back analysis according to the experimental results. The modified one inherits all the merits of the original criterion and the roughness angle is determined by a quantified roughness metric. In the current study, the modified Maksimovic criterion is validated using experimental data of rock joints. The good agreement between the calculated values and the measured ones indicates that the modified one has the ability to evaluate the peak shear strength for rock joints.

By using the data acquired from laboratory and field monitoring program, this study assessed the displacements of high-strength geotextile used as basal reinforcement of a closing levee. The displacements of the geotextile were monitored by high stiffness, large gauge length and measuring range SDW-100 displacement transducers with 500 kN/m high-strength woven geotextile .The transducers were first calibrated in a multi-function test machine. The tensile test of the geotextile yielded a tensile stiffness of 8314.4 kN/m. The field monitoring data indicate that: (1) The displacements of the geotextile at the base of the closing levee showing a concave shape and maximum displacement occurred along the center line. (2) The displacements of the geotextiles is explicitly influenced by the movement of the attached toe-berms. (3) The measured maximum strain is 11.9% which is equivalent to 837.40 kN/m in tension. The high strain indicates that the geotextile with higher tensile stiffness should be used. (4) The stress redistribution between the stages of the construction is observed. This phenomenon is further verified by numerical simulation using Plaxis. (5) The strain of the geotextile is a function of the closing levee backfilling rate. An appropriate backfilling rate should be selected to limit the strain in geotextile. (6) With the same tensile strength, the larger elongation can accommodate faster construction.

The nonlinear phenomenon which the passive earth pressure behind the retaining wall of both sand and cohesive soil is nonlinear distribution could be explained by the soil arching effect theory. The formula which calculated passive earth pressure coefficient of which assumed the stress state method and the soil wedge static equilibrium method were derived considering the soil arching effect, assumed arch as circle and the angle of slip surface as Rankine’s theory. Then, the distribution of lateral earth pressure considering the soil arching was derived by the above formulations; also the formulas that calculating the magnitude and the point of application of lateral passive earth pressure were derived. The accuracy of proposed method is confirmed by comparing with the experimental tests and values from existing equations. Finally, the trends of distribution and the height of total passive earth pressure of clayey soil are studied; distribution of passive earth pressures considering the soil arching is likely an exponential curve; and the height of resultant earth pressure point is gradually reducing with increasing the ratio of soil-wall friction angle to internal angle δ/φ.

Through collecting 76 groups of the in-situ stress data in underground water-sealed storage cavern in Chinese mainland, including Zhanjiang, Huangdao, Yantai, Huizhou, Jinzhou, Dalian, the distribution of the vertical stress，the largest horizontal principal stress( ), the minimum horizontal principal stress( ) and the lateral pressure coefficient(k) varying with depth in Chinese mainland are established. Then the features of the in-situ stress are corresponding regression analysed refer to the analysis method of Hoek and Brown. The results indicate that: (1) The shallow in-situ stress in underground water-sealed storage cavern in Chinese mainland show increasing trend with the increase of depth, showed a good linear relationship with depth, and the stress gradient is a little less than 0.027, in Hoek-Brown relation. (2) and are increased with depth, scattered points are mainly distributed in an inclined parallel belt. (3) Lateral pressure ratio k is dispersed when depth is less than 200 m, and centralized when depth is more than 200 m, and the envelope curve of lateral pressure ratio is distributed between the maximum and minimum envelopes of Hoek-Brown curve; it is approach the global distribution law. Through above research, the distribution law of in-situ stress field in underground water-sealed storage cavern in Chinese mainland is analyzed and summarized; it can provide references to the planning, constructing and developing of petroleum (gas) strategic reserve in Chinese mainland.

Geomechanics magnetic model test is a new test method that simulates gravity field with electromagnetic force field to study geomechanical engineering problems. In geomechanics magnetic model test, the magnetic field is achieved by solenoid and the similar material is made from the mixture of ferromagnetic material and rock-soil mass. The magnetic force, which is decided by the magnetic flux density gradient, will act on ferromagnetic material when it is put in a gradient magnetic field. In order to simulate the uniform gravitational field, a magnetic field with same magnitude and unidirection is needed in a certain space. According to the principle of magnetic circuit design and from different perspectives, three different kinds of magnetic circuit are presented to obtain the requisite magnet field to load the ferromagnetic material. In the optimum test space, the open type magnetic circuit can make full use of the magnetic field so that its magnetic flux density gradient can reach a larger quantity when the current is same; but the uniformity is not as good as expected. Taking advantage of the assumption of no magnetic dispersion, the closed type magnetic circuit has a better performance than the open ones. Comparing with the other two magnetic circuits, though the semi-open type is slightly inferior in terms of weight and efficiency, the uniformity of magnetic flux density gradient is the best of all; whose error is within 5%. In addition, because of the distribution of the coils and the test space, it is more convenient to arrange the testing instruments and loading device. Therefore, the semi-open type magnetic circuit is the optimal choice as the magnetic field generator for geomechanics magnetic model test.

Great changes occur both in the breaking form and structure of hard and thick overlying strata. Aiming at conditions of coal seam II2 overburden thick quartz sandstone in Rujigou coal mine by using field measurement, numerical simulation, theoretical analysis, field tests and other methods, we studied the features of fractures development, the breaking movement of rock, characteristics of strata behaviors, and technology of broken roof control of the overlying hard and thick rock, providing a basis for disaster prevention of working face with hard and thick roof. Research results show that the microstructure of this kind of quartz sandstone is compactive and completion; a large area vacant and great breaking movement appeared in the strata, which cause the strong dynamic load of support, and even result in reversed air flow in working face, and link up invisible burning area at upper mined-out areas. Obvious separate strata space generated after the rupture of hard and thick strata, and main fracture zone form at the top of working face and the middle part of mined-out areas, the height of main fracture zone is greater than the experience value; and disasters can even be caused when the upper mined-out areas meet the fracture zone. By applying deep-hole blasting at open-off cut to break roof and lowering mining height, it effectively shortens the initial breaking span of hard, and thick strata, and reduce the dynamic load in support and the height of main fracture zone.

To understand the sensitivity of factors influencing pillar stability, pillar arrangements in different sublevels are counted. Based on the local pillars in Dayingezhuang gold mine, pillar safety factor formulas of different forms were derived. Using six factors-five levels technology to design the experiment to analyze sensitivity of impact factors; at the same time this paper studies the relationships between pillar safety factor and pillar width, mining depth and room width. The study shows that the size of sensitivity of these factors affecting the stability of the pillar has been obtained via orthogonal experiment method and diminishes in turn : pillar width, mining depth, room width; in addition, the pillar safety factors follow the exponential function with the pillar width growth; follow power function with the mining depth decrease; and follow the exponential function with room width decrease. According to the pillar safety factor regression equation which is based on DPS and Matlab software, the minimum size of single-form pillar arrangement which satisfies both stability and security of the pillar has been reasonably obtained after analysis. Column width should be no less than 3.6 m; square column width should be 5.9 m or lager; and the room width should be no more than 8 m, which will certainly provide identifiable ground for the arrangements of pillar in deep middle section.

By consulting domestic seismic study on tunnel entrance, large scaled shaking table model tests of the entrance on homogeneous upward slope, slope with weak intercalation and strengthened slope were carried out in laboratory. General conclusions were obtained through analyzing the failure modes of the upward slopes. Under the earthquake, tension cracks appeared first at the shoulder of the slope, with the excitation acceleration increasing, soil at the shoulder started to dump and collapse; when introducing the weak intercalation, the soil at the toe of slope was squeezed broken firstly, tension cracks of the surface appeared at the weak interlayer positions, overlying soil sliding along the weak interlayer and leads to large-scaled soil collapse; the strengthened slope remained stable under the action of the force, only caused partial soil failure; minor axial cracks appeared at top. By analyzing the tunnel structure failure, the test results show that the fracture distribution on the A and B linings of tunnel portal are more complex than that on C and D linings; the total length can be taken as the earthquake affect length, which corresponds to 40m at the actual project. Affected by the weak interlayer, the fracture of the lining parts crossed the weak interlayer are more complex than others; the slope reinforcement can improve the stress state of both the slope and portal structure. These conclusions can be for reference in design and construction of tunnel under earth quake.

The bridge piers located in the ice-plagued area are influenced by hydrodynamic pressure and dynamic ice-load under seismic action. Based on the Morison hydrodynamic theory and Croteau dynamic ice model, a simple calculating model for the time-history analysis subject to seismic effect for pier column structures in the ice-plagued area has been proposed; and its effectiveness has been verified with the shaking table test; the effect of ice mass and water depth on pier column has been analyzed as well. The results show that the maximum curvature at the bottom of pier with ice increased by 8.93 times than the case without ice. The ice mass corresponding to the maximum curvature of the cross-section at bottom of pier increased with the water depth. The maximum displacement of pier can exceed the limiting displacement easily with the increase of ice mass, which leads to a sudden collapse of bridges, and should been taken a key consideration in the aseismatic design of bridge.

The most of construction coal mines in South of Sichuan province have been discovered with the difficult problems of much soft surrounding rock, easily weathering、developmental joint and fracture、large deformation、difficult support、multiple repairmen , which have influenced on the process of coal exploration and production in recent years. The soft style and severity should be conformed in order to choose the appropriate support technology. We investigated the engineering geology and choose the thick-bedded dark grey mud rock mainly surrounding the roadway. The fresh rocks with irregular shape have been tested by the point load testing in tunnel. After the screening testing data with the method of Grubbs criterion, the rock strength has been calculated by the formula defined by the traditional method、International Society for Rock Mechanics (ISRM) standard rate and Chinese engineering standard specification. The random and system error about the result of calculation with different formulas is tested by the F-test and t-test. The results show that the average uniaxial compressive strength obtained by the traditional method and ISRM standard rate is more accuracy than the Chinese engineering standard specification. The strength is appropriate to the soft rock evaluation. The change factor of the mudstone strength is between 11%-30%, which is approach to the general uniaxial compressive strength. The point load testing is the credibility, fast, convenience and cheap way to obtain the strength of soft rock with difficult coring, which could be used to evaluate the difficulty of the soft rock engineering.

By analyzing the records from stiff sites, soft sites and liquefied sites in 2011 Ms 6.3 New Zealand earthquake, the characteristics and relationship of ground motion on 3 types of sites including the liquefied sites are investigated. The seismic acceleration records at 23 seismic stations whose epicenter distances are less than 50 km and PGA great than 0.05g are collected, in which 3 stiff sites, 11 soft sites and 9 liquefied sites are included. The comparison results of amplification coefficient spectra from 3 types of sites indicate that there are obvious distinction among the stiff sites, soft sites and liquefied sites. From the view of ground motion, the liquefied sites can become an independent type. On the liquefied sites the high frequency component of ground motion decreases and meanwhile the low frequency component significantly amplifies. Compared with non-liquefied sites, the response of the short period structure on the liquefied sites will be reduced by half; but at the same time, the response of long period structure on the liquefied sites will be amplified by 2.5-5.0 times. The influence of liquefaction on the damage of CTV building in Christchurch City in the earthquake is significant because the predominant period of acceleration spectra increased to 0.5-1.0 s from 0.1-0.3 s, which is tallied with the natural period of the building about 0.7 s; and the response of the building increases as the consequence. As a result, the existing structure design method would be dangerous for the structures with long period in the liquefiable sites and the seismic ground motion in the liquefiable sites should be specially considered from the viewpoint of vibration.

For composite lining tunnel, initial liner is the most dangerous when temporary supports are dismantled before construction of second-layer liner. A project example of Qingdao metro is introduced. Using in-situ monitoring and numerical simulation, this paper contrasted deformation of rock and initial liner before and after dismantling temporary supports. Security of dismantling temporary supports is analyzed. Measured data show that volume growth and growth rate of displacement are small. Displacement results of numerical simulation are well consistent with measured data. The results show that the security of initial liner is little influenced by dismantling temporary supports. As a result, this study provides evidence for information-oriented construction of tunnel as well as experience for the future related projects.

Based on rule of stress diffusion, diffused fictitious soil pile model was constructed and the response of soil-pile under axial dynamic loading in inhomogeneous soil was investigated. Firstly, complex stiffness of different soil layers beside pile was gotten by using complex stiffness transfer model of radial multi-zone plane strain. And then combined with boundary condition, initial condition and continuity condition, the dynamical equations of diffused fictitious soil pile and real-body pile were solved from the bottom up. After that the analytical solutions of dynamic response at pile top in frequency domain and the relevant semi-analytical solution of dynamic response in time domain were gained. Finally, the influence analysis of angles of diffused fictitious soil pile, thickness of diffused soil layer, inhomogeneity of lateral soil of pile and length of pile were carried out. Based on diffused fictitious soil pile model, characteristics of the pile-soil coupling interaction in vertical vibration were gotten. The results can provide theoretical basis for dynamic pile design and testing.

According to numerous in-situ investigations of earthquake disasters, it is widely regarded that underground structure is of key significance for seismic design of underground cavern. Since no specified simulation methods are definitely issued in the specifications for seismic design of hydraulic structures in China, three common seismic calculation methods of underground structure including quasi-static analysis method, response spectrum method and time-history method are discussed. Numerical calculation are conducted using these methods for underground powerhouse structures of Yingxiuwan hydropower station under Wenchuan earthquake; and calculation results are analyzed based on the in-situ investigation of earthquake disasters. The results show that three methods can reflect the dynamic failure of underground structures to some extent and provide a theoretical basis for the seismic design. It is also shown that the calculation results of the quasi-static analysis method is prior to more safer design and unreasonable for simulating top arch and corbel; response spectrum method can estimate weak parts of structure, but not exactly in interaction analysis of concrete structure and surrounding rock; time-history method is able to precisely simulate the seismic response process under the earthquake disaster; and calculation result is best consistent with in-situ investigation of earthquake disasters, which is better for precise and economic engineering design. Time-history method is suggested to be used for dynamic calculation for the underground powerhouse of high level security, large-scale or in high seismic intensity region.

Foundation of Wudu gravity dam has the complex geological conditions, developed many adverse geological structures including faults and interbed shear zones. The stability of dam foundation is very serious due to the potential natural sliding paths formed by these interlaced planes. In order to study the impacts of multi-structural planes on foundation stability and reinforcement measures, a 3D numerical computation is conducted to analyze the typical dam section #19 of Wudu project by means of finite element method(FEM). First, the sensibility analysis is performed to study the impacts of various weak structural planes on stability. It reveals that the dam stability is severely affected by faults 10f2 and F31 incline downstream from dam heel, and the reinforcement measures should be taken and focus on the faults 10f2 and F31. On this basis, another sensibility analysis of concrete replacement depth is also conducted. Through varying the concrete replacement depths for faults 10f2 and F31, the corresponding safety factors are obtained. Results show that the reasonable replacement depth for faults 10f2 and F31 is about 19 m which can achieve favorable reinforcement effect; deformation and stress of dam have been improved; plasticity states of the dam foundation has been significantly reduced; the safety factor of anti-sliding stability is significantly improved; and the requirement of design specification is satisfied simultaneously. These research results provide an important scientific basis for the reinforcement of Wudu project, and also have the reference value for the stability analysis and reinforcement treatment of other similar projects.

Coral reef is a special engineering construction site, which is influenced by geological origin, biological effects, marine hydrodynamic and geological environment, etc. The research on engineering geological division is not only important in understanding and evaluating the engineering properties of coral reef deposits, but also has important guidance on coral reef engineering design and construction. Based on field geological survey, in-situ tests, drilling and a large number of laboratory experiments, analyses are conducted for geological origin of coral reef stratum, landform, stratigraphic configuration, mineral and chemical composition, and physico-mechanical properties of coral reef sediments. It is concluded that coral reef in the coast of Sanya can be divided into lagoon depositional area, sandbar area and underwater live corals accumulation area. Finally, evaluation is carried out for the engineering characteristics of each division, and suitability of construction is analyzed. The results have important guidance for geological survey of coral reef and engineering planning & design.

An open trench was excavated at the field, the falling weight deflectometer (FWD)is adopted to replace the impact loads, and the vertical displaces in the near areas behind the trench are measured with the sensors of the FWD. The geotechnical parameters of the fields are in-door tested; the nonlinear dynamic finite element software of ABAQUS is adopted to establish a two-dimensional model, in which the far elements are defined as infinite to simulate the absorbing boundary; and so the vibration caused by wave bounces at the boundaries are avoided; and the FEM model is modified according to the in-situ tested vertical displacements. The vertical displacements of different conditions are simulated; the factors that influence the vibration isolation effects are analyzed; such as trench depth, trench width and distance between trench and impact loads. Some conclusions are drawn as follows. (1) The vibration isolation effects increase when the distance between trench and impact loads decrease; but in the actual vibration isolation engineering, the trench can not be constructed much near to the impact loads to guarantee the stability of the trench walls; so the distance between trench and impact loads should not be considered as an important factor in the vibration isolation design. (2) As to improve the vibration isolation effects, to increase the trench depth is much effective than the trench width, and a narrow and deep trench usually need much less excavation than a wide and shallow trench. (3) When designing the vibration isolation of normal civil and industrial buildings for impact loads, an open trench with 0.5-1.0 m width and 2.0-2.5 m depth is relatively reasonable by considering the isolation effects, excavation and maintenance fees; it is proved to be reasonable by comparing with one vibration isolation engineering.

Prestress loss of anchor cable should not be neglected in engineering construction. The cause of prestress loss is usually related to engineering site condition. The saturated silty sand is more complicated and sensitive than other geological conditions, which is more likely to cause prestress loss. Through real-time monitoring of anchor prestress of a deep foundation pit in Langfang city, combining with the engineering environment, factors influencing on variation of anchor prestress are analyzed. The results show that the process of construction, tension and environmental factors affect the variation of prestress. The most obvious impact is the excavation process; and the maximum rate of variation of prestress value is 79.1%; instantaneous unloading causes values of prestress loss between 22.8% to 59.2%. The influence of construction process is most obvious. Experience for similar geological engineering construction is provided through the research and analysis of variation law of anchor prestress.

Because of the existence of confined water at the bottom of the deep foundation pit soil， when the weight of impervious soil above cannot balance with hydraulic head，improper construction method can easily lead to piping， the instability of foundation pit enclosures and many other problems. In this paper, many risk sources related confined water are analyzed and many specific requirements are put forward for survey, design and construction. Because the foundation pit is near the river and there are penetration channels between confined water and river water, so the change of river water level will cause the rise or fall of confined water head. In view of the design head was reference the change of groundwater level in nearly one year, not considering the head changes throughout the years, which become the hidden danger caused accident. In the end, the river water level rising during construction, confined water pressure exceeded expectations and caused the piping. After the accident, water channel was soon clogged. And then concrete was poured into soil at the bottom of foundation pit. The soil property improved and thickness of impervious soil increased significantly. Piping problem was resolved and the project was completed safety. Grouting method is an effective way to ensure foundation pit excavation safety when confined water head is larger. Research in this paper has a strong guiding role in controlling risk of the pressure water during design and construction, especially engineering near river or ocean.

In order to investigate the effects of different anisotropic shearing strength expressions on numerical computation results, the two-dimensional elastoplastic finite element analysis were carried out for an assumed rectangular underground cave in a layered rock mass for three cases, in which the empirical formulae for internal friction coefficient and cohesion of material which change with directions suggested by the first author and S. Pietruszczak were applied respectively. The stresses, displacements and plastic zones in the surrounding rock mass are compared. The results show: the computational accuracy of using the empirical expressions established by the first author matches basically with that of using the first-order approximations given by Pietruszczak; but there is a comparatively obvious difference between the computational accuracies of using author’s empirical expressions and Pietruszczak ‘s 2nd order approximations.

The shear strength of jointed rock masses is determined by the structural surface and the adjacent intact rock shear strength; When the structural surface is completely connected, the shear strength of rock mass is determined entirely by the structural surface. Monte Carlo method can simulate the spatial distribution of the discontinuity in jointed rock masses according to the geometry parameters of the structural surface; and then the connected structural surface can be searched via depth-first algorithm; and compared with the rock mass, the shear strength of the connected structural surface is the smallest; so it can be considered as the potential sliding surface of jointed rock slope. The stability of a series of sliding surfaces can be analysed by the limit equilibrium method. This method is the complement of the jointed rock slope stability analysis.

Underground caverns of Jiangping River Hydropower Station arranged for the diversion tunnel, flood discharge tunnel, spillway No.1, spillway No.2 in turn, caverns of which are intensive, geological conditions are complex and constructions are difficult. The authors simulate caverns mainly in three-dimensional model; while simulate the three chambers slopes of the outlet, four large faults , the actual shape of a number of rock stratification and slope table accuratly. Prestressed anchor cable, anchor bolt and lining systems and other support measures are used in the project after excavation. The prestressed anchor bolt is simulated accuratly in supporting calculations. System of anchor bolts are simulated by using two-dimensional submodel for equivalent calculations. These measures ensure the necessary accuracy, but also improve the modeling and calculation efficiency. For the secondary lining simulation, the shell unit of three-dimensional shell structure is used to get revised deformation parameters of the initial lining and secondary lining considering the effect of anchor bolt lining through two displacement equivalent. Lining thickness has been optimized according to the deformation trends of the key points and the greatest moment change of cavern. Cavern bending moment and shear force value can be read though lining unit effectively. Bending and shear force values of lining structural of the most dangerous condition provide a reference for the reinforcement. The diagram of displacement values and the plastic zone map before and after the reinforcement are given in the calculation results. And the reinforcement measures significantly reduce the maximum displacements and the plastic zone.

Firstly, an indoor model test was modeled by using the large-scale all-purpose finite element software, ABAQUS and 3D finite element method to verify the reliability of the stability analysis of cave structures. Then, based on the karst geological data of the contract section A11 in Yongan-Wuping highway, the karst caves were approximately regarded as the ellipsoids and the 3D finite element models were established to analyze how the stability of the embankment and the karst cave roof is influenced by roof thicknesses, filled heights, karst cave locations and filling conditions of karst caves. Also, the 2D plain strain finite element method was adopted to make a comparison with the prevailing method for safe thicknesses of karst cave roofs. Research shows that，for cave roof strata which are relatively intact, the safe thicknesses of cave roofs obtained by using 4 as the stability factor of safety of roof tensile failure are too conservative. The safe thicknesses of cave roofs obtained by the beam-slab theory of bending tensile failure are inclined to be conservative too. This is because the actual roof strata do not coincide completely with simplified hypothesises of the beam-slab theory. However, based on the beam-slab theory of bending tensile failure, the safe thicknesses calculated by the maximum bending moments obtained from the finite element analysis are the most economical. For actual karst caves which have obvious 3D effects，the prevailing simplified theory and 2D numerical analysis method are relatively coarse and the 3D numerical analysis method should be adopted. Through analyzing the above problems, the research work offers guidance to the embankments design and karst cave treatment of the highway in the karst regions. Good socioeconomic benefits are obtained. It can be used as a reference for similar engineering application.

The search of non-circular critical slip surface is a key problem in slope stability analysis. Essentially, this problem is a path search problem; so the ant colony algorithm is a very suitable method to solve this problem. To overcome the shortcomings of traditional ant colony algorithm, from the principle of combing one whole road by forward and reverse search of ants, here a new algorithm, meeting ant colony algorithm, is proposed. And then this meeting ant colony algorithm is used to locate the critical slip surface of slopes. Through two typical examples and an engineering application of a reservoir bank slope, the effectiveness of the new algorithm is verified. The results show that, from not only the whole search scope but also one point search scope, the meeting ant colony algorithm are all better than traditional ant colony algorithm; so the solutions diversity to search the critical slip surface of slopes by meeting ant colony algorithm is better. And then, to meeting ant colony algorithm, the global optimal solution can be included in the search scope by the larger probability; and the global optimal solution can be obtained by the larger probability. At last, by meeting ant colony algorithm, the critical slip surface of slopes can be found on larger scope and by larger speed.

Collapse of dangerous rocks is one of the most common geological dynamics hazards of high and steep shallow rock slope. It is sudden and strong, random, high speed and violent; so it is the focus of slope engineering survey. On the base of on-site investigation of dangerous rocks of Tibet Zhangmu Mountain, the distribution range of dangerous rock bodies is analyzed. The trajectory of collapse dangerous rocks, speed and characteristics of the body collapse accumulation of the different coefficients of friction is simulated by PFC3D in the condition of rainfall. The results show that the trajectory of collapse dangerous rocks is influenced by topography of slope, multiple impacts with the ground and repeated changes of direction, simplifying dimensional calculations may draw the wrong conclusions. Slope surface coefficient of friction affect the accumulation of forms of collapse of dangerous rocks, the smaller friction coefficient, the farther accumulation body position, and the easier performing flow state. Slope coefficients of friction 1.2, the simulation results are more consistent with the actual; The area of collapse dangerous rocks is the lower cliffs from Armed two camps to Zhangmu trench opening. PFC3D simulation of dangerous rocks collapse body movement can initially determine three-dimensional accumulation form and the influence scope, and provide a useful reference for disaster prevention and mitigation engineering design.

A new strength reduction finite element method is established based on the principle of strength reduction technology. We take the process of the strength parameters reduction as a brittle plastic stress drop course; and a strength reduction increment is set as convergence condition to determine whether the program out of circulation. The final reduction factor is the safety factor of slope stability. The theory can be easily extended to the three-dimensional slope stability analysis with high precision, and can find the sliding surface of the slope and its development tendency of failure. Through two case stidoes, the importance of the 3D slope model is shown; and it is suggested that when the geological condition is complex, we should carry out analysis from the three-dimensional angle rather than simply it to the two-dimensional problems.

Based on a site of a large span continuous rigid frame bridge in Shanghai, the influence of hydrodynamic pressures on ground motion is discussed. The input ground motion has been obtained by using the response spectrum of code, one-dimension model and two-dimension model. It shows that hydrodynamic pressures can reduced the vertical acceleration response significantly, while it has little effect on horizontal acceleration response. The ground motion calculated by two-dimension model which consider the topography is quite different from that of other two models. The predominant periods of input ground motion calculated by two-dimension model exceeds the flat section of response spectrum of code. Finally, the influence range of valley topography is discussed, which shows that the influence region in the direction normal to the river is no more than 5 times of soil layer thickness or 140 times of deepness of the river valley. Any structures in this region should take river valley influence into consideration.

Aiming at studying the evolution of the microstructure in the interface and quantitatively assessing the extent that friction coefficient influences the reinforcement performance, a three-dimensional discrete element model is established; and the strengthened node of triaxial geogrid is factually simulated by jointing the surrounding particles with the assistance of “clump” logic. The mechanical responses of reinforced soil and geogrid under pull-out loading are analyzed. Compared with the experimental and theoretical results of previous reports, the accuracy of the model used in this study is verified. Meanwhile, the variation law of meso-structure parameters, such as local void ratio and coordinate number are obtained. Afterwards, parametric study on friction coefficient is carried out, and it can be found that the apparent cohesion is positively related to the friction coefficient. However, the internal friction angle cannot increase continuously when friction coefficient reaches a certain value. The statistical results demonstrate that the improvement of macroscopic interface strength could be reasonably attributed to the optimization of microscopic fabric. The presented methods in analyzing soil-geogrid interface and achievements in this paper could provide a new understanding for mechanism analysis of reinforced earth structure.

Based on the hardening-soil model, finile element analyzing method was carried out on supporting system of gravity retaining wall with embedded H-shaped steel through PLAXIS FEM software; and researches was conducted on the deformation and stability of the support system with the simulation results and on-site monitoring data. Researches show that (1) Gravity retaining wall with H-shaped steel shows good feasibility and engineering functions in the range of 7-8 m of local excavation of shallow foundation pit, which can be the supplementary means of gravity-style enclosure. (2) Good precision and results close to actual situations can be obtained by hardening-soil model(HS model for short) embedded in PLAXIS FEM software to simulate the foundation pit, and parameters of HS model can be obtained according to engineering experience. (3) On-site monitoring data of foundation pit shows that the displacement development of gravity retaining wall with H-shaped steel was controlled under the restriction of retaining wall on both ends, which is good for global stability; and that H-shaped steel can well improve the stiffness of supporting system and resist some of bending moment produced by soil mechanics, which to some extent controlled the support system’s displacement. (4) In actual engineering local excavating depth of gravity retaining wall with H-shaped steel should be carefully chosen, which is advisably used under the condition of loose requirement for surroundings’ protection, with a advisable excavating depth of 7-8 m in local foundation excavation and the global excavating depth of 5-6 m. Through the research of gravity retaining wall support with H-shaped steel in shallow foundation pit in soft soil area, more reliable technique supports can be offered for relevant supporting engineering of foundations.

A homogenization method to analyze circular tunnel with rock bolts is presented, which can simplify this kind of complex mechanical coupling problem through considering the composite material of rock mass and rock bolts as a new homogeneous, isotropic, parameters strengthened equivalent material. Rock bolt density parameter is defined to reflect the influence of high density rock bolt support pattern; Mohr-Coulomb criterion is applied to the new equivalent material; the increasement of key coefficients for Mohr-Coulomb criterion is considered to related to rock bolt density parameter; thus equivalent Young’s modulus, equivalent cohesion and equivalent friction angle for circular tunnel with rock bolts can be derived. Displacements of tunnel with and without rock bolts are compared through the existed displacement solution. Based on this solution, the reliability index and failure probability of tunnel are calculated by considering allowable ultimate displacement as instability criterion. The results show that the tunnel with rock bolts is much reliable. It is shown that the proposed method is simple and feasible and the rock bolt can improve the stability and reliability of tunnel.

Non-linear finite element method (FEM) is conducted to simulate the dynamic construction of balance weight retaining wall building and new embankment fractional filling considering the mountain region highway embankment widening particularity. The effects of new embankment geosynthetic reinforcement and fill compaction condition on the embankment stability, slip surface behavior, settlement and retaining wall displacement are analyzed. The dynamic coupling relationship between embankment settlement and retaining wall displacement is investigated combined with the geotechnical centrifuge model tests which simulate the retaining wall different displacement modes in mountain region embankment widening project. The retaining wall displacement and embankment settlement, differential settlement are intercoupled. The embankment differential settlement will increase for the insufficient compaction under the equilibrator. The retaining wall leaning toward will induce additional embankment differential settlement. The pavement structure design should consider the magnitude modification of differential settlement induced by new embankment dead weight compaction.

Under the foundation of Green-Ampt infiltration model established upon ponding condition, we expand it useful to calculate infiltration rate and cumulative infiltration in the variable rainfall intensities. Combined with the theoretical basis, we discuss the differences between constant rainfall intensity with variable rainfall intensity and the effect of saturated hydraulic conductivity and soil types on the infiltration process under variable rainfall intensities based on the saturated-unsaturated flow software Hydrus-1D. Research shows that: compared with constant rainfall intensity, variable rainfall intensities is more easily from the point of the rain infiltration; and the cumulative infiltration increases significantly. When other hydraulic parameters unchange, the larger the saturated hydraulic conductivity is, the coincidence rate of the curve of infiltration rate and variable rainfall intensity changing with time is higher. And the control time of rainfall intensity and the cumulative infiltration are larger accordingly. Other hydraulic parameters effects cannot be ignored; because the effect of them on infiltration can achieve similar to saturated hydraulic conductivity. Correctly understanding infiltration process and influential factors of rainfall infiltration upon the variable rainfall intensity will help us to accurately grasp the actual situation. So it has important practical significance to guide hydraulic engineering.