Critical state is an important phenomenon exhibited in granular materials. Numerical simulations of two-dimensional particulate arrays are carried out using granular discrete element method based on void cells. The numerical simulation results are analyzed in detail to reveal the critical state from the viewpoint of microscopic geometric fabric. Based on the dilatancy of granular materials the micromechanical theoretical model of critical state in terms of valence is proposed. An implicit relationship between valence and plastic shear strain is obtained. The solution of the theoretical model confirms well with the numerical results. The important conclusion is drawn as follows: the parameters related to the microscopic theoretical model, including the critical valence and the plastic shear strain corresponding to critical state, are dependent on the microscopic properties such as the particle shape, surface friction, the consolidation stress and the initial void ratio of the granular assembly.

Cyclic wetting and drying usually occurs in rockmass for some reasons such as water level variation, which is fairly harmful for its long term safety. A series of uniaxial and triaxial compression experimental tests on sandstone under cyclic drying and wetting have been carried out. The corresponding complete stress-strain curves are obtained; and characteristics of deformation and failure are analyzed. Compared with the dry specimens, elastic modulus, cohesion, internal friction angle, uniaxial and triaxial compressive strengths of the specimens under “dry-saturation” cycling are all decreased to some degree. The general trend is that all mechanical indices have a relatively sharp decline after the first time saturated with water; and thereafter, decrease gradually followed by an increase in cycling times. The rock samples become more ductile under cyclic drying and wetting. Sandstone peak strength increases along with the increasing of confining pressure. The effect of confining pressure on peak strength is greater for dry specimens than for “dry-saturation” cycling specimens.

Mechanical characteristics of porous dolostone was conducted systematically in order to investigate porosity effects on mechanical properties of dolostone samples, which were sampled from surface and more than 5000 m deep in Southeast Sichuan Province. The porosity is one of the critical physical properties of dolostone, which is often categorized into storage strata of petroleum or natural gas. The porosity ranges from 6% to 12% for these samples of dolostone. The experiments in the laboratory were performed with regard to uniaxial compressive test (UCT), Brazilian Split test (tension strength), direct shear test, as well as triaxial compressive test (TCT). The results of uniaxial compressive tests indicate that the uniaxial compressive strength decreases with increase of the porosity in dolostone; meanwhile similar results were achieved in the multiaxial tests, namely, the strength reduces as increase of porosity at the fixed confining pressure; whereas the peak strength of the triaxial compressive stress increases with the increase of confining pressure when the porosity is fixed. Finally, the yield function of MSPDu (Mises-Schleicher-Drucker-Prager Universal) model was introduced, which was employed to porous dolostone; the results of porous dolostone show that MSDPu model can describe well yield properties of the porous dolostone.

To prompt the usage of scrap tires in civil engineering in China, the compaction properties of granulated tires and loess mixtures, with a granulated rubber content of 0%-50% by weight, were studied by standard and modified Proctor compactor and a cutting ring compactor specially designed by the authors for comparison. Test results show that the compaction properties of the mixtures are similar to that of loess soil when the granulated rubber content is less than 20%, but similar to that of a cohesionless soil when the content is more than 40%. A power function relationship was found between the maximum dry density and the optimum water content for mixtures with various compaction efforts. Compaction effort shows less effect on the maximum effective dry density of mixtures with granulated rubber content of 10%-30%. A power funtion relationship is existed between optimum water content and granulated rubber content. Test data show that 30% and 40% of granulated rubber is an optimum addition content for granulated rubber and loess mixtures. Compaction parameters of mixtures have been proposed for design based on laboratory test results.

Soil-water characteristic curve(SWCC) describes the relationship between suction and volumetric water content of unsaturated soil which are not one-to-one correspondence. This curve performs hydraulic hysteresis during arbitrary drying-wetting suction changes are applied to the material. Based on capillary hysteresis internal variable model and conventional soil-water characteristics theory of unsaturated soils, a modified model which can simulate soil-water characteristic relationship during arbitrary suction changes is proposed. This model increases one parameter compared with the capillary hysteresis internal variable model, which describes the reversible changes of water content and ensures the slope of scanning curve not to be infinite when scanning curves approach the boundary of SWCC. The modified model retains the precision of the capillary hysteresis internal variable model simultaneously. Compared with experimental results in references, this model is able to simulate soil-water characteristics relationship of unsaturated soils better than the capillary hysteresis internal variable model. Determination method of the new parameter is also discussed.

The coefficient of earth pressure at rest, i.e. K0 is one of the important mechanical parameters for analysis and computation in geotechnical engineering. In engineering practice, the mechanical behavior of backfill is anisotropic due to compaction. Some sand samples with different sedimentation directions are made. Anisotropy of sand is revealed by triaxial drained tests where bedding planes of the samples are horizontal and vertical respectively. Measurement method of K0 is given on the basis of development of strain path test machine. The effect of different sedimentation directions on the K0 value is investigated. And comparison is made among test results, the results predicted by Jaky’s equation and those got by centrifuge model tests. The effectiveness and accuracy of the test method of K0 is confirmed by the centrifuge model tests of earth pressure. The results show that the neglect of the effect of anisotropy will underestimate K0 value and make the earth pressure underestimated.

Based on a metro station structure of three stories and three spans at a liquefiable ground, a series of shaking table tests is conducted, in which the acceleration response, strain response and horizontal displacement of the station structure itself are tested. And the pore water pressure, acceleration and seismic subsidence of the foundation soil are also measured. This paper mainly analyzes the dynamic response rules of the foundation soils under the influence of liquefaction effect and it also summarizes the development law of pore water pressure for liquefaction ground around station. Moreover, seismic subsidence characteristics as well as the dynamic soil pressure on the side walls are concluded. The results indicate that the structure has an obvious effect on the distribution of the pore water pressure field. At the same depth of soil, the peak of the pore water pressure of each measured point near the structure is less than that far from the structure. The dissipation rate of the pore water pressure is gradually slowed down from bottom to top. The structure has a movement upward relative to the foundation in the process of earthquake; and the floating phenomenon is obvious under strong ground motion. The dynamic earth pressure of the side walls is decreasing with increased depth; and the earthquake characteristics have a significant influence on the dynamic earth pressure.

Using the compaction test, liquid-plastic limit combined device to Atterberg index, wax sealing method to dry density, gas meter to carbon dioxide and exchangeable sodium percentage test, as well as the composition and fabric of clay mineral, the physical and chemical actions of stabilized soil with cement-based soil stabilizer were researched. The experimental results show that the maximum dry density of the mixture increased and the optimum water content decreased as the dosages increased. After curing the mixture of stabilized soil, the plasticity index reduced, the dry density enhanced, the carbonate content increased, and the exchangeable sodium percentage raised. The clay mineral was activated to become all kinds of silicate and aluminate under the condition of stronger pH value and calcium ion. The study indicates that the mixture has gradually formed the more compact monolith in the system of soil and soil stabilizer and water and gas, through the transformation from liquid and gas to the solid, as well as the effect of fill, pack and cementation. The cation exchange has the minus effect in the later stage on the stabilized soil. The aluminosilicate clay mineral has been divided to take part in the action of the silicate and aluminate under the condition of the stronger pH value and calcium ion.

In order to understand factors affected gas permeability of unsaturated clayey sand, through rebuilding triaxial apparatus, it can be used to measure gas permeability of unsaturated soils. The modified apparatus has advantages as follows: such as structure simpleness, making model expediency, good model uniform, stable loading system, comprehensive measuring pressure gradient, enhancing measuring precision. And it resolves problems that measuring gas volume no easy. At same time it resolves a problem that gas flow out rigid wall and model edge. The relationship between flowing velocity and coefficient of permeability is given by that apparatus, under different dry densities and different water contents. Flowing velocity of unsaturated soils can be expressed by Darcy law under the range of water content and dry density in this test. The function of gas coefficient of permeability, water content and dry density are given from a great deal of test data.

Based on the simplified model of the unit of particles, the basic principles and characteristics of the unit of particles were analyzed; and considering the deformation and strength of sand with the effect of intermediate stress, the interaction properties of the units of particles were discussed in detail. The effects of intermediate principal stress on the strength of sand were analyzed from the results of previous triaxial texts. Some macro features of the effect of intermediate stress on strength of sand were interpreted in view of meso-scale study through the analyses of the basic states and properties of the unit of particles, the features of macro-pore and unit pore, the interaction properties of the units of particles and relative physical mechanism. The macro features include that the strength of loose sand is improved gradually if the intermediate principal stress increases from the minor principal stress ?3 to the maximum principal stress ?1; but the strength of dense sand is improved at the beginning and reduced if the intermediate principal stress approach the maximum principal stress ?1; the segment of constant strength increases with the increase of sand density; the rate of strength improvement is effected by the initial ratio of sand if the intermediate principal stress is close to the minor principal stress ?3.

Unfrozen water content is not only an important evaluation index of water migration in frozen soils, but also a common parameter in thermotechnical calculation. Six types of soil samples (totally 76) which are collected from the permafrost of Da Hingang Mountains on the section of Daqing-Mohe in the China-Russia oil pipeline project are measured by calorimetry at such temperatures as about -0.5℃, -2℃, -5℃ and -10℃. The principle and equipment of calorimetry are introduced firstly. According to a large number of test data, The analyses of the influencing factors and their variations of unfrozen water content, which include temperature, soil type and initial moisture content are made. The representative values of unfrozen water content at four given temperature in the six types of soils are obtained through statistical analysis. The coefficients of unfrozen water contents at different given temperatures are obtained by normalizing the unfrozen water content and plastic limit water content. The empirical formulas for unfrozen water contents in clay, silty clay, silt and peat soil are given through fitting unfrozen water content, plastic limit and temperature with power function. Finally, making comprehensive analysis of temperature, soil condition and initial water content, we get binary linear regression equation on unfrozen water content, initial water content and plastic limit water content, so as to provide reference for actual engineering.

In traditional shaking table test semi-infinite foundation is difficult to consider; whereas in numerical simulation dynamic fluid-structure interaction is hard to calculate. To deal with the two difficulties, a newly developed real-time dynamic hybrid testing method is employed to solve the dynamic soil-structure-fluid interaction problems. Taking an aqueduct for example, the aqueduct-water system, called experimental substructure, is physically tested on a shaking table; while the semi-infinite foundation, called numerical substructure, is numerically modeled by a lumped-parameter model. The data exchange between the two substructures is performed in real-time; thus the dynamic response of the whole coupled system can be evaluated. Meanwhile, the finite element analysis is also implemented to simulate the test model. The comparison of the tested results with those obtained from the finite element analysis demonstrates that the real-time dynamic hybrid testing can achieve good test accuracy for this dynamic interaction problem. The tests of the soil-structure interaction (SSI) effects for different soils show that the soft soil reduces the structure response amplitude and extends the response period. With soil becoming hard, SSI effects decrease and the structure responses will ultimately converge to the solutions of rigid foundation.

By using the particle discrete element method, a three-phase (aggregate, mortar and interface) meso-scaled concrete model is developed for investigating dynamic behaviour of concrete materials with an efficient pre-processing approach. Based on the presented model, the dynamic splitting tensile tests of concrete with different loading rates are performed by numerical simulation. The dynamic increasing factor (DIF) and failure patterns of concrete sample with different strain rates are obtained, which match quite well with the experimental results. The research indicates that, the higher the strain rates, the more cracks there are, which become reticular formation as well. Some of the cracks even penetrate the aggregates. Therefore, this process might require more energy comparing with the static process, which, in a sense, explains the higher strength of concrete in dynamic process. Further more, the force chain bifurcates at high strain rates; and the randomlity and nonuniformity of space distribution increase; consequently the dynamic strength of concrete has a stronger discreteness.

Xiamen subsea tunnel is the first undersea road tunnel in China. The tunnel passes through the weathered strata F1, F2, F3 and F4 where the rock mass is weathered and fragmented, the main rock in this region is weathered and fragmented granite. The main mechanical characteristics of this kind of rock especially the strongly weathered granite is low strength, high compressibility, self-stability and bearing capacity of the rock is poor; it brings many exceptional problems to the liner design and the tunnel construction technology. In order to study the mechanical characteristics of the host rock in weathered strata, a series of laboratory tests for the rock including slightly weathered granite and strongly weathered granite have been carried out; the triaxial test results containing triaxial compression test and creep test of strongly weathered granite show that this kind of rock has the properties of low strength, large deformation and low elastic modulus; plastic flow will occur after the stress-strain curve reach the peak; and also the friction angle and cohesion are determined as about 31°and 0.1 MPa respectively through Mohr-Coulomb criterion; more over, high creep potentials of strongly weathered granite is shown through the triaxial creep test. Based on the triaxial test results, a rheological mechanics model suitable for host rock in strongly weathered strata was established through the creep test results. The results obtained from the research work are useful for soft rock engineering especially for weathered granite engineering, and it has guiding effect on the tunnels’ design and construction for this kind of rock.

Tiaxial compression tests are made with different number of geotexile. It gets the parameters of Duncan-chang model for reinforced sand with 1, 2 and 4 geotexie layers. When 1 or 2 layers, the geotexile has a little restraint on the sand’s lateral deformation and the failure mode is shear failure. When 3 or more layers, the failure mode is tensile failure. Under the two failure modes, the existence of reinforced material can influence the cohension force which is nonlinear increase with the layer’s number, but not the inner friction angle. It defines the coefficient of the enhanced action which has a nonlinear rise according to the layer’s number. When axial strain below 5%-8%, the sand is at the elastic distortion stage, but elasto-plastictity stage when above 8%.

The slopes of loading, unloading curves of stress-strain relation and the slope of the corresponding elastic strain-plastic strain curve(e-p curve) are critical constitutive parameters. They play important role in elasto-plasticity, damage theories and the analysis of elastic and plastic deformations. The three slopes are mutually related. Here, a difference-type and a differential-type identities of the three parameters are respectively derived theoretically and verified later with the test data of a coal sample. The results show that these two identities are both correct. Then an application of the slope identity to studying the relation between the elastic and plastic strains presented by Li You is given. It is found that the “translation relation” of e-p curve in - space is equivalent to an equality of two slopes ratios.

Field tests were conducted at a pile-net structure subgrade working point of a certain new railway to investigate the load sharing and transfer between piles and soil in pile-net structure subgrade, also the composition and distribution of tensile force in cushion. In which the deformation of foundation, the pressure at the bottom of embankment, the pore water pressure, the axial force of pile shaft, and the tensile force in grid were tested. We can get the results as follows. Firstly, compaction subsiding is major component of foundation settlement, indicating the subgrade is stable. The thicker the soft soil, the larger the foundation deformation. Secondly, the soil arch exerts fully when the ratio of settlement difference between pile and pile-inter soil to piles net distance is 5.93%. The subgrade load raised later will undertaken by piles completely. Thirdly, the distribution of vertical additional stress along with the depth of reinforced area shapes like a “K”. Fourthly the distribution of tensile force in bar strip shapes like a “M”, and the thicker the soft soil ,the larger the tensile force. Fifthly, the tensile force consists of two parts,. One is caused by subgrade loads, and the other is embankment’s lateral sliding. The two parts must be considered when designing the bar strip.

To study the seismic damage mode and dynamic characteristics of road embankment, firstly, the road embankment seismic damage of Wenchuan Earthquake is investigated finding out that the main seismic damage type of road embankment is rip of upside and bulge of downside of the slope. Road embankment seismic damage is associated with seismic intensity, revetment measures, and reinforcement measures of road embankment noumenon closely, and has no significant relation with embankment height and crossfall of the ground. By means of shaking table model test and numerical simulation, it is found out that the magnitude and the increment of acceleration and dynamic shear stress are the largest in the upside of the road embankment, which is in the same position of the rip. Also, dynamic earth pressure and displacement are the largest above the berm, which is in the same position of bulge. All of rip and bulge are in the depth of 3 m, which show that the road embankment damage is a superficial zone damage. By dynamic numerical analysis finding out that magnification factor of peak ground acceleration (PGA) shows three types: monotone increasing as the height increases (h <10 m), increasing to decreasing and later increasing again as the height increases (h >20 m), and the form lies between the formers (10 m

The erodibility change of estuarine sediment in the process of consolidation directly determines the resuspension and secondary migration of sediment, which plays an important decisive role in estuarine and coastal stability. The rapid deposition of Yellow River sediment into the sea was simulated on the tidal flat of the modern Yellow River delta, and the erodibility and physico-mechanical properties of the sediment at different consolidation times were measured in situ. The results show that the anti-erodibility of the Yellow River sediment into the sea rapidly increases with consolidation time; and the critical erosion shear stress has already exceeded the value of the undisturbed tidal flat surficial sediment when the consolidation time extends as long as 8 hours. The critical erosion shear stress of the newly deposited sediment has a good positive correlation with bulk density, penetration resistance and shear strength, a good negative correlation with water content. The rise rate of measured critical erosion velocity of the Yellow River sediment into the sea with consolidation time is higher than the rise rate of calculated value using different formulas; and the former is 1.5-4.1 times as high as the latter.

The uniform seismic ground motion is usually emloyed to analyze the slope stability under earthquake. But in fact the seismic ground motions are varied with time and space. The slope stability under multipoint and multidirection seismic ground motions is an important topic. Based on the generalized slice method of the forces and the moments equilibrium the limit equilibrium equations of slope under multipoint and multidirection are derived; and the method to solve the dynamic safety factor is given. In this derivation, the seismic ground motions under each slice of slope are varied with time and space; and the horizontal ground motions are not fully incoherence with the vertical ones. Finally, two examples are analyzed to verify this method feasibility.

A cyclic horizontal displacement solution of subsoil is of great concern in aseismic design of foundations and underground structures. Herein a double-layer model is adopted to simulate horizontal strata and to provide a theoretical simplified displacement solution in frequency domain which considers an existing liquefiable soil layer. Meanwhile, the relevant displacement of subsoil under arbitrary loading in time domain is also presented by the cycle-by-cycle method. Using a proper porewater pressure incremental model for horizontal soil strata, the moduli of subsoil is updated cycle by cycle to simulate the nonlinear process of subsoil caused by liquefaction. The results of shaking table test are consistent with the calculated results. It is shown that the method proposed can describe the process of liquefaction fundamental influence on subsoil displacement. The proposed method which is of clear physical meaning can represent the basic model of influence of liquefaction on subsoil displacement; and it can be used for non-dimensional analysis in time and frequency domains.

The polypropylene bar shell bolting shotcrete and support system was studied on the basis of the analysis of the mechanics principle of shell structures. The technique feature is a kind of specially three-dimensional bar-mat reinforcement instead of three-dimensional bar-mat. It has very high mechanical property and was applied in difficult drift without profiled bar, anchor bolt, grouting and so on. The model experiment was done by relying on the industrial test on the broken laneway of Xishan Coal Power Company. The distortion, destruct shape, developmental rule of the supporting system were examined while the stress and strain distributing rule and also the ultimate load were obtained. The application showed that without reducing the carrying capacity of supporting the case, and heavy metal stent compared to the steel supporting the form of reduced consumption and the amount of concrete rebound, and has good flexibility, is an excellent soft rock drift Jean pressure retaining structure, and has good prospects for widespread application.

The effects of surcharge and pseudo-static seismic forces on soil slopes were investigated by applying the kinematical approach of limit analysis theory and strength reduction technique. The rotational failure surface was considered and analytical expressions is derived to calculate the safety factor of slope subjected to surcharge and earthquake loading. The upper bound solutions for analytical expression are presented by applying iterative optimization method. From the comparative analysis, it can be seen that the solutions presented here agree well with available predictions both in simple static state and dynamic state. Parametric analysis shows that the safety factor of slopes decreases nonlinearly as the stability condition of a slope deteriorates when an increase in values of slope angle, surcharge and pseudo-static seismic forces occurs. From the numerical results, it also can be seen that latent slide surface moves inward to the slope with the increase of surcharge q and horizontal effect kh and the decrease of vertical effect kv, sliding surface and failure mass becomes bigger. The effect of vertical seismic acceleration on the stability of reinforcement slopes is significant especially for strong motion earthquake; i.e. that the effect of the vertical seismic acceleration should be taken into account in the engineering practices.

Based on the analysis of the characteristics of underground blast induced surface ground motion, the evaluation standard of the effect is discussed. By analytical method, the computational model of surface ground motion and the response spectrum are established. The calculation shows that: There are two wave groups in the surface ground motion, when estimate their effect on above-ground structures, that the periods of the second wave group is 1.5－2.0 times longer must be considered. The response of the above-ground structures are determined by the natural frequency and damping, the frequency and amplitude of the seism. For miniature blast equivalent, the effect of frequency of the surface ground motion could be ignored; but for great blast equivalent, the effect of the frequency could not be ignored. For double layer buildings, the motion of the second layer has the characteristic of big amplitude.

Foundation bearing capacity is one of the most important research topics in the field of geotechnical engineering. Focusing on circular shallow foundation, and starting from spatial problem, and according to the theory of limit analysis, a more reasonable upper bound solution for the ultimate bearing capacity of the three-dimensional circular shallow foundation is presented theoretically. This thesis chooses a suitable foundation failure mode and motor displacement velocity field, and firstly considers the influence of the lateral soil pressure on the limit bearing capacity of circular shallow foundation and the effects of soil weight under the base of the foundation and surcharge load. Combined with the project, the upper bound solutions are calculated using corresponding Matlab program and compared with the serve value in other techniques. The upper bound solution is proved to be more rational and practical.

The metro 11 line shield tunnel passing through the Suzhou River, will impact on the security of flood wall for Suzhou River. The pile foundation relative to shield tunnel was raised and a “double span” portal frame was adopted to ensure the appliance of shield tunnel. Not only the security of flood wall is assuring, but the space for shield tunnel is adequate to the demand. The diversity in the stress and deformation construction of flood wall with shield tunnel or not, was analyzed by constitutive model built on the finite element method. Before shield tunnelling the deformation of bed plate foundation is consistent in it of continuous beam, both the middle part of long pile and the top part of short pile are detected in the extrorse deformation; and the stress rule of the whole structure accord with inherent characteristic of the portal frame. After shield tunneling the deformation of bed plate foundation is similar to it before shield tunnelling; the maximal deformation lies in the middle part of the tunnel upside. By contraries, after shield tunnelling both the middle part of long pile and the top part of short pile are detected in the introrse deformation. The deformation of long pile is in the form of bending deflection, and the maximal deformation lies in the neighborhood of the tunnel axle wire, the deformation of short pile is in the form of rigid body deformation; the maximal deformation lies in the bottom of itself. The theoretical settlement calculated approximates to the practical settlement tested; it is shown that the influence on the deformation of the flood wall by shield tunnelling is of controllable condition.

The physical properties of rock would be varied with its weathering process levels. Combining with the stress state of anchorage cable in homogeneous rock mass and distributing rule of shear strength in transverse isotropy elastomer under interior symmetry load, the distributing equations of shear strength of anchorage cable in transversely isotropy elastic rock mass are deduced. Assuming that the elastic modulus of weathered rock changes with exponential function, the analysis results show that: ① The shearing strength of anchorage section would increase (or decrease) with the increase (or decrease) of the elastic modulus which change with the depth of weathered rock. ② The shearing strength of anchorage section near to the load-bearing plate would increase with the decrease of anchorage cable boring radius. And the shearing strength changes obviously with the shear modulus of weathered rock. ③ The shearing strength on anchorage section interface close to the load-bearing plate would change with the shear modulus which is in the surface perpendicular to the surface of rock. The research results will provide references to design of anchorage cable in practical projects.

The limit equilibrium theory is used for analysis of heave resistant stability factor of foundation pit, which becomes dependent upon ‘deterministic’ properties of soil and slide surface. Considering the strength reduction principles and movement unit law which is used to limit equilibrium theory, a ‘deterministic’ analysis model of heave resistant stability factor of foundation which is adapted to different types of slide surfaces is established. Based on the ‘deterministic’ analysis model, reliability analysis of chance constrained programming is established in light of the randomness of the calculating parameters and the constraint condition; there may be no satisfactory strength parameters in the latter one. The calculation and comparison are carried out in view of circular sliding surface and Prandtl’ sliding surface. The influence factor of inserting ratio of deep braced excavation is analyzed for different circle centres, load on excavating pit bottom and bracing load on retaining structure. And also the control of random constraint function for the inserting ratio is studied. As an example, the analysis in light of the theoretical idea is taken out in some engineerings.

Although the interaction among piles should be calculated by Geddes’s stress method, which can not consider the raft rigidity, it can’t be applied to pile-raft interaction. Geddes’s stress method is modified and the modified calculation models is verified in practice. The balance settlement method based on variable rigidity which can reduce differential settlement and hypo-stress is introduced through adjusting the array of pile group.

Salt heaving is the main disease of sulphate saline soil; and the key point of ground treatment for airport engineering is to eliminate salt heaving. Experiments about salt heaving under different loads were carried out to study the restraining effect of load on sulphate saline soil with different compaction degrees and saltnesses; and salt heaving formula which can calculate salt heaving rate was deduced. Control guideline of ground treatment by heavy cover replacement technique was discussed: compaction degree shouldn’t be too high, the suggested value can be picked from 90% to 95% when ground carrying capacity is adequate; feeble sulphate saline soil can be used for filling 2 meters below pavement, the suggested saltness is lower than 0.5%; water dangerous point produces the worst danger, so drainage design should be taken into consideration seriously. The method and flow chart for calculating the least load and the least thickness was given. Calculation indicates that 50 kPa is almost enough to control salt heaving; the least thickness is about 2 meters with grit stone for cover. Heavy cover replacement technique will be used widely in ground treatment in airport engineering with sulphate saline soil in Northwest China.

Research on failure criterion and evolution process of deformation instability of tunnels has been one of the hot issues and difficulties in underground engineering field. Based on the synergetic theory and chaotic dynamics, different stages of tunnel excavation and nonlinear dynamics evolution characteristics for the whole process of deformation failure on surrounding rocks are presented. The whole process is divided into three stages as equilibrium stage, nonequilibrium-linear stage and nonequilibrium- nonlinear stage. The fluctuation correlation mechanism of the whole tunnel system is revealed by systematical analysis; and then the nonlinear dynamic evolution model is established. By combining the practice project with the length of time sequence for general deformation monitoring data as well as the effective analysis by chaotic dynamics, the dynamical criterion of the stability evolution process of the tunnel system is conducted separately under different data sequence lengths (more than 3 000 and less than 3 000). According to unstable and failure features of each evaluating stage of the tunnel system, the dynamic criterion is proposed. This criterion is employed to get a stability judgment of an overlapped tunnel in Guangzhou metro, of which reasonability and reliability are testified. This research has a great significance for the stability judgment of the surrounding rocks of tunnels.

By using Mohr-Coulomb constitutive model, a three-dimensional numerical model was established for layered non-homogeneous subgrade of Suzhou Light Rail Transit Line 1; and the influential law of tunneling on neighboring loaded piles were also studied. Based on the numerical simulation results, with the increase of difference between soft and hard strata of layered non-homogeneous subgrade, the inflection point appeared at the loaded single pile due to tunneling; and the pile settlement also increased. The upper part of the loaded single pile in upper soft and lower hard strata had larger positive bending moment; while the larger negative bending moment happened at the lower part of the pile disposed in upper hard and lower soft strata. In contrast to the loaded single pile in homogeneous subgrade at the same position, there was larger axial force presented to pile top and pile tip of the loaded single pile in upper soft and lower hard strata; but the smaller axial force occurred at pile top of the loaded single pile in upper hard and lower soft strata. The horizontal displacement distribution of the front pile in loaded pile group which beared different concentrated loads coincided with the loaded single pile at the same position; while the deflection of the back pile was less than the loaded single pile. Besides, the influence caused by excavation of shield tunnel in layered non-homogeneous subgrade to the internal force of loaded pile group was more significant than the deformation.

Based on proper damping parameters, a finite difference numerical simulation is conducted for the seismic analysis of the Baihetan underground caverns. Wavelet packet analysis is made for the evaluation of wave propagation and spectrum characteristics of seismic response from the point of view of peak acceleration and vibration energy. Results indicate that seismic intensity increases with the elevation and fault zones possess vibration-suppressing effect. Spectrum characteristics of seismic response can be clearly revealed by wavelet packet. High-frequency components of seismic wave are gradually absorbed during propagation. A major influential frequency band of peak acceleration and vibration energy spectrum characteristics is obtained as 1-3Hz for wall rock, and other bands have minor effects.

The large scale of soil liquefaction in Bachu-Jiashi earthquake in Xinjiang Autonomous Region on 24 February, 2003 is the most notable phenomena of sand liquefaction in China mainland since the Tangshan Great Earthquake in 1976. In terms of the investigation in Bachu-Jiashi area, the feasibility of conventional cone penetration test (CPT) to evaluating liquefaction, including Chinese code method, the Robertson method and the Olsen method, is inspected. The results show that the prediction success ratios of Chinese code, the Robertson and the Olsen methods used for the Bachu earthquake liquefaction prediction overall higher in non-liquefied sites than those in liquefied sites. The prediction success ratios are 88%, 71% and 88% for the non-liquefied sites; but 55%, 73% and 45% for the liquefied sites respectively, which are dangerous and reason should be identifed in the future. Also, an appropriate local liquefaction prediction method in Xinjiang region has to be established.

Liquefaction data from five major earthquakes, i.e. Kobe, Tonghai, Tangshan, Chichi and Haicheng earthquakes, are collected. The features of liquefied sites are comparatively analyzed to inspect the difference and link. The analytical results show the depths of liquefied layers and the groundwater tables in liquefied sites are obviously different. The depths of liquefied layers mainly are 0-2 m, 2-6 m, 4-6 m and 2-8 m and the groundwater tables mainly are 0-1 m, 1-2 m, 1-3 m and 1-3 m in Tonghai, Tangshan, Kobe and ChiChi earthquakes respectively. The depths of liquefied layers are located from 0 m to 20 m while the groundwater tables are from 0 m to 9 m in ChiChi earthquake, which are the largest ranges. The numbers of standard penetration test (SPT) counts from the earthquakes are similar and mostly are 5-15 counts; but the numbers in ChiChi earthquake vary the most significant with a maximum value more than 30. The average shear wave velocities of the liquefied layers in the earthquakes are considerably diverse. The shear wave velocities are less than 150 m/s in Haicheng earthquake but mainly concentrated in 150-200 m/s in Kobe earthquake. The shear wave velocities in Chichi earthquake mainly are 150-250m/s with an average value of 200 m/s. Sites with shear wave velocities more than 250 m/s liquefied, which disputes previous acquaintance that sites with shear wave velocities more than 210 m/s cannot liquefy.

Longyou grottos, the ancient underground grottos with the characteristics of shallow embedding, large span and some others, have been attracting many experts of rock mechanics and engineering geology coming to research. Recently, many positions of the roof of grotto No.3 have the phenomenon of cracking and exfoliating. The data of strain meters installed on the steel pillars which have the function of supporting the grotto are also changed. What the strength of rock pillar No.3-2 decreasing leads to the adjusting of strength condition of rock around is thought to be one of the main reasons causing the changes mentioned above. With the aid of FLAC3D, the paper simulates the changes above caused by the strength decreasing of rock pillar No.3-2, using the main fundamentals of strength reduction technique for reference. The results of the numerical simulation explain the changes get by monitoring. Based on which, the paper analyzes the change of stress of the roof and other rock pillars of grottos No.3 in the process of deformation and failure of rock pillar No.3-2. By the research, the authors get the points: ① The strength of rock pillar No.3-2 has been decreased a little; and still it is in the process of continuous decreasing. ② The cracks on the roof will be longer and more in the process. The conclusions provide a basis for analyzing reasonably, forecasting the strength state of grottos and protecting the grottos in the process of deformation and failure of rock pillar No.3-2.

It is found that the conventional equivalent linear method underestimates the peak ground acceleration of the soil layer earthquake response under the strong earthquake input in practice. The phenomenon is proved by calculating and analyzing the record data from the site effect borehole station array. The reason is that the artificial value of the equivalent shear strain is quite larger than the real shear strain in high frequency band and it reduces the contribution of the high frequency components of the site soil layer earthquake response. Studies show that the shear strain changes with the frequency; the shear strain-dependent shear modulus and damping was proved in the experiments; so the shear modulus and damping are supposed to be frequency-dependent. Based on this assumption, how the high frequency component of the earthquake input motion is filtered by the soil layer caused by the equivalent shear strain reduction factor is discussed. Meanwhile, the frequency-dependent stiffness and damping are applied to the equivalent linear method and the feasibility is discussed by numerical calculation. The accuracy of the proposed method is examined by comparing with the record borehole data from large earthquakes, for example, the Port Island borehole record data in Hanshin Earthquake of 1995. The proposed method always gives much better results than the conventional equivalent linear method; so that the high frequency component can be reasonably considered.

Based on the Jinping second stage hydropower station, a distribution diagram of faults, is obtained from the geological diagram at Maomaotan lock site. A power-law relation between fault number and fault size is proposed, i.e. - . Two power exponents are estimated by using linear fitting in two segments. It is found that the power exponent D has a value of 0.48 if fault lengths r are shorter than 0.1 km; while the power exponent is equal to 1.49 if fault lengths r are longer than 0.1 km. Combining with Monte Carlo method, the spatial distribution of a further small scale of joints can be obtained. Finally, the discontinuous deformation analysis (DDA) is employed to numerically simulate and analyze the excavation of the Dashuigou underground powerhouse; and the stress and displacement plots resulted from excavation in highly jointed rock mass are obtained.

Inshore saline soil can be solidified respectively and jointly with cement, lime, flyash and polymer SH agent for increasing the anti-deformation and the strength in air and water of the solidified soils. Triaxial compression test of six solidified soils have been carried out for studying the deviatoric stress-strain properties of the solidified soils. Generally, the deviatoric stress-strain curves of solidified soils with cement and lime and that with lime and flyash are strain softening; that with lime are strain hardening. On the basis of the results of triaxial compression test, SH agent can increase the strength of solidified soil in air and water; furthermore, the strain can be increases at the maximum strength, i e. anti-deformation and elasticity of solidified soil is enhanced. It has been proved that the solidified soil with 0.9% SH agent and 12% lime and 36% flyash has the well properties, such as lightweight soil, higher strength, and well elasticity, in addition, it can decrease settlement of road foundation because of the lightweight soil.

I11-conditioning of least squares will lead to parameter solving failure. Based on analysis of foundation settlement prediction model and matrix inversion theory, using regularization theory, a new regularization unbiased estimation settlement prediction model algorithm is proposed. Unbiased and minimal variance of this new algorithm is described according to statistical theory. Existence of regularization parameter in the new algorithm is proofed in some condition. Calculation formula of regularization parameter is also given. Analyses with literatures and engineering examples show that the algorithm proposed not only reduces the matrix condition number and alleviates matrix ill-conditioning degree, but also can get the prediction model parameters effectively.

In order to depict the discrete properties near the retaining wall on the meso-scale, while efficiently reduce particle numbers and save computation time, based on coupled discrete-continuous approach, a retaining wall under seismic excitation in centrifuge model test is simulated. Particle flow code(PFC), which is based on discrete element method, is used to simulate sands near the retaining wall, while the domain containing particles away from the retaining wall is simulated as continuous media by the fast Lagrange analysis of continua (FLAC). The motion of the retaining wall is governed by a self-edited dynamic finite element program which is added to PFC. Coupling is achieved by interchanging data between the two software during each time step. The essence of the coupled approach includes two parts: (1) fulfilling the continuity between the discrete and continuous domains; (2) the macro parameters of the granular material should be in accordance with those used in continuous model. A new approach for picking up coupled forces and a free-vibration column simulation method are presented as supplements to satisfy the two above mentioned requirements respectively. It is shown that, on the meso-scale, the coupled method can well describe the concerned zone and the interaction between the retaining wall and the particles.

The statistical data of disasters caused by earthquake show that underground structures are more likely to be damaged when they in complicated geology and geological environment, such as nonuniform stratum, soft soil, soft interlayer nearby, etc. The seismic response of the metro station in the site with saturated soft interlayer is hereby analyzed. On the basis of the explicit finite element methods of dynamics analysis about single-phase and fluid saturated porous media, taking into account soft interlayer existing in the surrounding soil, a seismic response analysis method which can be used in metro station structure-saturated soil coupled system is established. By numerical modeling, the seismic responses of the key positions of metro station structure are shown under three actual earthquake recorders with different spectra characteristics which incident as the plane P wave. The factors, such as the location and thickness of the soft interlayer, are discussed in their influence on the dynamic response of metro station structure. The study results show that the soft interlayer has a very negative amplification on the dynamic response of metro station structure; and the amplification is the most unfavorable when the soft interlayer inside the metro station.

Considering elasticity and steady-state creep of mudstone and salt rock, numerical experiment approaches are employed to study mechanics and time-dependent law of bedded salt rock under uniaxial and low confining pressure triaxial loadings; the effect of creep rate mismatch between salt rock and mudstone on the creep of bedded salt rock is analyzed. Finally, composite material research methods of laminated composite are preliminary discussed. It is shown that the initial concentrated stresses induced by elastic parameters mismatch are relaxed in the process of creep; stress redistribution induced by creep rate mismatch between salt rock and mudstone is exhibited; interlayer(mudstone) with relatively small steady creep rate obviously influences the creep of bedded salt rock. These analyses reflect the nonlinear creep behavior of bedded salt rock, so as to lay the basis for establishing constitutive law in the future.

According to the explicit finite element method of ABAQUS and 32 CPU parallel computing cluster platform of the research group, a three-dimensional refined finite element model for cross tunnels is established and used to research the 3D nonlinear seismic response of cross tunnels under near-field strong ground motion and compare the results with that of one-layer upper/lower tunnels. The results show that: compared with a single deep/shallow-buried tunnels, for any one-layer upper/under tunnel of intersecting metro tunnels, the relative horizontal displacement difference of the tunnel top and bottom is magnified; and the seismic stress of intersecting tunnels is reduced; the seismic stress on the left side of tunnels is larger than that of the right side; and the seismic stress of tunnel spandrel and hance is significantly greater than that of other parts; and the tunnel spandrel is the most dangerous part of the tunnel structure. The acceleration response of top and bottom at the under tunnel of intersecting metro tunnels is larger than that of the upper tunnel; the interaction influence of intersecting metro tunnel on the seismic response of any one-layer upper/under tunnel is related to the cross form of intersecting metro tunnels and the characteristics of the inputted near-field ground motion.

Electroosmosis consolidation provides a potentially attractive soil improvement technique, which involves the application of a direct current potential across electrodes embedded in the soil and cause the flow of pore water from the anode toward the cathode. The traditional electroosmosis theory cannot provide satisfied solution due to the hypothesis of constant parameters of mechanical and electrical properties of soils. In this paper, FEM software is developed to couple the Laplace equation for electrical field with Biot’s equation for consolidation; and the displacement of soil mass and pore water pressure can be obtained during electroosmosis process. The nonlinear relationship among electrical resistivity, void ratio and effective stress is incorporated in the control equations. The calculation results of both one and two dimensional model agree well with the analytical solutions. The software can simulate complicated boundary conditions and predict the settlement process of the soil layers. Furthermore, the software can provide useful data for system design of electroosmosis treatment technique.

Initial stress field is the basis of the stability evaluation of underground engineering. In initial stress field analysis of Dalian underground oil storage cavern，based on site stress test data, a new method of inversion of initial stress field is proposed. Firstly，the relationship between initial stress field and elevation is established according to the analysis of measured stresses. Secondary, because the direction of principal stress and model coordinate axis do not coincide, the stress must be transformed. Finally, inversion of initial stress field is completed with functions using the Hoek-Brown rock mass strength criterion. The functions are defined with the programming language FISH embedded within FLAC3D. Through the comparison between calculated stresses and measured stresses, it is shown that the proposed method has higher inversion precision, smaller error and meets the needs of engineering, which reveals that it is a practical, simple and effective method.

The existence of the representative elementary volume (REV) is the premise of continuous-media method to study in rock mechanics; therefore the investigation of the REV of fractured rock mass is a fundamental problem in rock mechanics. Whether the REV occurs could be viewed from different physical parameters. However, the existence of REV is analyzed in term of blockiness, which is defined as the percentage of the volume of isolated blocks formed by fractures in the total rock volume. The basic analysis process of GeneralBlock software is presented and a three-dimensional fracture model is set up by this software. Thirty-five kinds of rock mass structural models are established considering the 5 types of persistence and 7 kinds of spacing, which were suggested in the fracture classification of ISRM. For each of the 35 structures, rock blocks are identified by GeneralBlock; and the fluctuation of blockiness with the variance of the scale of model region is investigated. For each structure, the calculation is realized 5 times at random respectively in a specific range of model to reduce the influence of randomness. The results show that the size of representative elementary volume of fractured rock mass is between 4 and 8 times of the fracture spacing; for all of the 35 structures, no more than 8 times.

Following Muki and Sternberg’s method, the passive isolation of vibration due to moving loads using pile rows embedded in a poroelastic half space is investigated. The responses of the poroelastic half space is governed by Biot’s theory, while the pile is described by the 1D bar vibration theory. Using the free field solution for a moving load applied on the surface of a poroelastic half space and the fundamental solution for a harmonic circular patch load applied to the poroelastic half space, the second kind of Fredholm integral equations in the frequency domain describing the dynamic interaction between pile rows and the poroelastic half space is developed. The time domain responses for the pile-soil system can be obtained by using IFFT arithmetic, then, the isolation vertical vibration effectiveness is obtained. Comparison of our results with some known results shows that our results are in a good agreement with existing ones. Numerical results of this study show that velocity of moving loads has an important impact on the vibration isolation effect of pile rows. The same pile row has a better vibration isolation effect for the lower speed moving loads than for the higher speed ones. Also, the optimal length of piles for higher speed moving loads is shorter than that for lower speed moving loads.

The construction of the 3D visualization model and the numerical model of complex geological body is critical in mine, geotechnical, hydraulic and hydropower projects. Aiming at the disadvantages of modeling complex geological body of mine by numerical simulation software, such as the modeling process complex and difficult and mesh generation has great workload, Combined with the advantages of modeling complex geologic body of mine use mine software, on the base of studying the differences between wireframe model and block model, a kind of new method of numerical modeling and geologic body visualization based on complex mine is proposed based on wireframe model. According to the different characteristics of wireframe, taking surface and cavity model as examples, an effective method of converting Surpac surface model and solid model into MIDAS/GTS numerical model exactly is researched; this method has been used to research the cavity stability analysis of Dongguashan Copper Mine successfully. The results show that the new modeling method is feasible and effective, so as to offer a new modeling method for mine design, safety analysis and complex geological body rock soil engineering numerical simulation, etc.

The occurrence of rock burst is related to the distribution of abutment pressure. In order to study dynamic variation laws of abutment pressures of C-shaped stope, vertical stress fields in coal mass during advancing process of island working face were simulated. The plane distribution characteristics of abutment pressures and the dynamic evolution characteristics of strike abutment pressures and lateral abutment pressures in coal mass were analyzed; and conclusions were drawn as follows: (1) the distribution of vertical stress in coal mass is C-shaped; (2) the influence distance of lead abutment pressure of island working face is 3-5 times higher than that of normal working face; (3) the peak of abutment pressure reaches its maximum when the advanced distance of the working face is equal to the length sum of two nearby working faces. Finally, the engineering example was analyzed. The results can provide a basis for prediction and control of rock burst.

Based on the discrete element method (DEM), the model of particle flow for frozen sand clay has been established, the contact-bond model among balls is adopted in the simulation test. According to this model, the contact bond strength was employed to simulate the cementation of ice in the frozen sand clay. Comparison between the results of numerical simulations and laboratory tests under different temperature and confining pressure, the results shows good agreement between them. It is similar to the macro properties of frozen sand clay that the parameters of particle elements have the property of evident temperature-dependent. The results are valuable for developing the applicability of the DEM to analysis of special soil.

Due to the limitation of the numerical models of anchors by finite element method (FEM) in geotechnical engineering at present, an anchor model which is fit for the strength reduction FEM is put forward. Strength reduction FEM considering the anchor model is proposed. The corresponding program is also developed; and the proposed model and method are tested by a case study calculation results of a simple rock slope reinforced with anchors. At last the model is used in evaluation of a soil slope stability; and the results of this example indicate that the model is convenient and feasible.

The influence of cushion thickness on the settlement of cement-soil mixing pile composite foundation was studied by the static load tests and numerical simulation. The static load tests of natural foundation and four cement-soil mixing pile composite foundations in which the cushion thickness was different were carried out for the silt soil in Zhuhai area. The settlement-tubes and magnetic rings were pre-buried in the foundation. And the probe with scale was used to detect the positions of the magnetic rings and obtain the data of the layered settlements. According to these experimental data of composite foundation for four cement-soil mixing piles, the settlement law was analyzed; and layered settlements of piles and soil in different composite foundation were calculated by numerical calculation. The comparison between the different composite foundation shows that the settlement of pile could be reduced by the cushion, but the thickness of cushion has a significant influence on the supporting capacity of composite foundation — a much thicker cushion could weaken the supporting capacity and increase the settlement of composite foundation. For choosing the optimal thickness of cushion, the geological condition was suggested to be considered except for the supporting capacity and settlement of composite foundation. The cushion thickness could be from 20 cm to 40 cm — the higher value is selected when the silt layer is below the middle sector of pile, conversely the lower value is selected.