In order to investigate the effects of hydration state on the stress-strain-strength behaviour of compacted expansive soil, a series of mechanical property tests under one-dimensional consolidation and triaxial compression are carried out under two typical hydration states which are both saturated. The conventional saturation method is adopted for the first hydration state, while the second state permits samples swelling to steady state. The results show that there is a significant difference of volume expansion between the two hydration states; and the volume expansion rate is influenced by both the deformation constraint condition and the length of seepage. Compared with the first hydration state, the soil sample under the second hydration state has greater compression index λ , swelling index κ, and lower elastic shear modulus. The effective internal friction angle is 77.2% of the corresponding value of the first hydration state, which reflects the variability of saturated shear strength of the compacted expansive soil. The yield phenomena of consolidation curves can be observed with the yield stresses 123.2 kPa for the first hydration state and 94.5 kPa for the second hydration state. Under the first hydration state, the samples present strain softening and shear dilatancy at lower confining pressures, while they present strain hardening and shear contraction at higher confining pressures. Under the second hydration state, the samples present shear contraction and weak strain softening. The samples under the two hydration states show overconsolidation in the process of consolidation and shear loading. The overconsolidation is not due to preconsolidation pressure only; however, it is partially caused by that swelling of the soil is constrained in the process of loading. Under the different hydration states, the expansive soil has both different initial void ratios and different swelling potentials, while the interaction of the swelling potentials with external constraint conditions, drainage conditions and stress states leads to the complex stress-strain-strength behaviour.

Heavy metal ions in soil may lead to the change in soil engineering properties. Their leakage would also harm the surrounding environment. The published literatures show that cement solidification technology can effectively improve the strength characteristics of heavy metal contaminated soils. Considering pollutant type and content, cement content and curing time, a series of experiment programs and theoretical analyses were performed to study the strength characteristics of heavy metal contaminated soils stabilized/solidified by cement. The test results show that the presence of metal contaminants will reduce soil strength; but as the increase of the cement content and the curing time, soil strength will be significantly enhanced. It is noticed that different pollutant types and contents will bring different influences; NaCl can promote the early strength of cement; but the CuCl2 and AlCl3 will hinder the cementation reaction during curing.

For deep foundation pit nearby metro stations, the excavation scheme has significant influence on the deformation of foundation pit and construction safety. A deep foundation pit adjacent to metro tunnels in Shanghai is investigated as the research background. The foundation pit is divided into a big part and a small part in the design scheme. A feasible excavation scheme is proposed to excavate the big part firstly. This investigation is mainly performed to analyze the impacts of excavation sequences on the deformations of the retaining walls and tunnels. Centrifugal model tests are introduced to study the deformation behaviors of the retaining walls and tunnel structures. The analysis results show that excavating big part of the pit firstly is more reasonable to control the deformation of foundation pits. The conclusions have some instructions for designs and constructions of similar engineering.

Basic properties and microstructures of two typical silty clays collected along Beijing-Tianjin high-speed railway and Hangzhou metro line are studied. Using triaxial testing apparatus by GDS Company, static tests under consolidated undrained condition and dynamic tests under high cycles for simulating long-term traffic loading are carried out on these two soils. The undrained static strength, dynamic strength, critical dynamic stress ratio, development of accumulated dynamic strain, and shear strength after vibration of both soils have been studied for comparison. It is found that the soil along the Hangzhou metro line is with high water content, low density, large void ratio, which leads to weak strength and high sensitivity compared with those of Beijing-Tianjin’s. After small amplitude cyclic loading, both of the undisturbed specimens behave higher shear strength than that under static condition, while after large amplitude cyclic loading, vice versa. The remolded specimens always show a strength reduction after cyclic loading, no matter the amplitude of dynamic loading.

Convective heat transfer between the air and the pipe wall and evaporative heat removal from the surface of the soil bared in the small holes of the pipe wall are two modes of heat transfer in duct-ventilated embankments with perforated ventilation pipe. The effects of perforating ratio, wind velocity and water content on convective and evaporative heat transfer by the wall of the perforated ventilation pipe are analyzed. The formulae for heat transfer coefficients of convection and evaporation in the perforated ventilation pipe are obtained. The total cooling effect in duct-ventilated embankments during winter is mainly dominated by convective heat transfer due to weak evaporative cooling based on smaller unfrozen water in frozen soils. During warm time, the effect of convective heat transfer between the ambient air and the pipe wall may raise the temperature of the embankment soil, whereas the effect of evaporative cooling by the small holes of the pipe wall is significant due to large unfrozen water content in unfrozen soils, thus being able to partially or completely balance out the heating effect in the embankment due to convective heat transfer and to ensure the embankment stability.

The dynamic characteristics of the tubing string for solution mining of oil/gas storage caverns are studied preliminarily. It is implied that the buckling of tubing string will induce damage and failure of tubing. Through the preliminary study of vibration characteristics of tubing string without space constraint, the critical velocity expression of tubing string in an ideal condition is obtained. Computation analysis shows that the tubing string without space constraint will generally suffer buckling due to fluid-solid coupling vibration; and the inner casing will reach buckling prior to the out casing generally. Considering the importance and complexity of this problem, the influences on the critical velocity analysis mechanical model of conditions, axial force, fluid pressure, solution mining cycling method, horizontal constrains, and the coupling of axial liquid hammer and transverse vibration, are discussed roughly. Finally, considering space constraint, some research advices on the all-sided analysis of the tubing string dynamic characteristics are proposed.

By constructing the confined disposal facilities for contaminated dredged sediments from lakes in China the thick clay layer is usually chosen as a natural barrier. Because the clay layer will undergo a large-deformation consolidation due to the overburden of dredged material, the soil deformation should be considered by investigating the transport and transformation of contaminant in clay barrier. Based on the Gibson’s one-dimensional consolidation theory and the dispersion-advection equation of contaminant in saturated porous media, a theoretical model for coupled large strain consolidation and solute transport is herein presented, in which soil weight and biodegradation effect are first taken into account. Using numerical solutions of the derived model the transport and transformation of contaminant in a deforming soil layer are first studied thoroughly; the effects of different parts and parameters of the model are then analyzed respectively. It is shown that the large deformation of soil has complex effects on the transport of contaminants in clay layer. On one hand, soil deformation can accelerate the transport speed of contaminant, and on the other hand, decrease of coefficient of permeability due to soil consolidation is able to increase the breakthrough time of contaminant. These two different effects rely on many factors, such as the thickness of soil layer, adsorption ability of soil, etc. The obtained results from this study are meaningful by assessing the separating capacity of natural clay barrier for contaminant transportation.

The fractal structure is a common phenomenon of soil. Through analyzing influence domain(Voronoi domain) of the fractal structure connection point, the bearing capacity of particle connection is converted to stress intensity. Some beneficial results are obtained. Values of fractal dimension of particle system structure influence soil strength obviously. The particle of basic unit is more, the ring from the particle is longer, the space for the ring is larger; it is more instable in mechanical property, the strength is lower. The stage number of fractal structure determines the size of the maximum pore. The stage number of fractal structure is more, the size of the maximum pore is larger, the equivalent stress intensity is lower. The couple stress intensity is inversely proportional to the area of basic structure unit (two-dimensional). That is to say, the basic structure unit is larger, the couple stress intensity is lower. Therefore, it can be concluded that the particle is larger, the couple stress intensity is lower when other conditions are same.

On the basis of preparation and characterization of calcium-based hydraulic consolidant, this paper makes a preliminary study of consolidation conservation of historical earthen sites under moisture circumstance. Analytic results of scanning electron microscope and X-ray diffractometry show that Ca(OH)2 are transformed into a kind of acicular secondary CaO with diameter 50 nm and length 200 nm after being calcined, and this nano-sized secondary CaO are transformed into oval plate-like Ca(OH)2 with size 200-300 nm after being slaked. Meanwhile, research results indicate that calcium hydroxide crystals undergo both substantial size reduction and clear morphological change, developing nanometer, plate-like and acicular crystals upon aging. Results of consolidation experiment of moist earthen samples reveal that permeabilities of nanometer lime-alcohol dispersions are superior to that of analytically pure Ca(OH)2-alcohol dispersions, and consolidation effects of calcium-based hydraulic consolidant are obvious. It is possible that calcium-based hydraulic consolidant will become a new consolidation material used for conservation of historical earthen sites under moisture circumstance.

Usually a physical model can be built to simulate the failure process of slope and study the instability mechanism of slope, while inclined model is a typical loading method to simulate the failure process. As a loading method, the controllability of loading mode and similarity of stress field during inclining process are significant points that can influence the application of the method. In order to study the controllability of test, taking bulk slip mass for example, the influences of inclined model and centrifugal loading methods on anti-sliding safety factor of slip mass are analyzed. The results show that anti-sliding safety factor decreases persistently with the inclination angle increasing in the inclined loading mode. But the anti-sliding safety factors of centrifugal loading test are influenced obviously when the acceleration is in the range of 1g-10g(where g is acceleration of gravity). In order to compare the similarities of stress field in the model before and after inclining, a numerical model of physical slope is built to simulate stress fields with different inclination angles. The results show that the stress state in the middle of slope keep steady; the stress state in the front part of slope changes greatly when the inclination angle is larger; variation of local stress field is propitious to simulate the failure process of reservoir landslide. In order to verify the application effect of the inclined model to landslide failure process, a slope model test is taken based on the prototype of Qianjiangping landslide; the failure process of landslide is obtained. Comparing with the results simulated by discontinuous deformation analysis (DDA) method, the failure form obtained from inclined model test is closer to the real condition of landslide.

The main research way of the surface subsidence due to underground mining is local observation and prediction based on the probability integral at present. These ways for studying surface subsidence is only can observe and infer the phenomenon of the subsidence; it is not study of the law for the movement process of the whole rock up the coal mining room. The rock stratum near by the surface will form a bend band when the ratio of the depth of the embedment and the thickness of the coal seam up long-wall mining coal face is very large. The bend band is one of key rock stratum near surface. Presumed this key rock stratum is controlled the rate and shape of the subsidence basin and the rate is far below the key stratum rock thick. Used the theory of key stratum to estimate the location of the rock stratum near surface and selected the suitable bending function, the surface subsidence basin model is set up by the way to survey the elasticity sheet. Discussed the applicability scope and parameter determine of this model is. This model is taken into consideration much factor of the rock stratum up the mining room, so the ideal for this model is more progress than use the probability integral function to predict the surface subsidence.

With the project of Jintan underground gas storage, taking the cavity actual bearing conditions as the object of study, carrying out unloading confining pressure test of salt rock under different conditions, the complete stress-strain curves, deformation characteristics are obtained. The test results show that axial and radial strains increase slowly in the initial stage of unloading confining pressure; and the relation between strain and confining pressure is linear. Along with the confining pressure continuous decrease, axial and radial strain values increase sharply. Comparing the loading and unloading curves, under the conditions of the same maximum principal stress, when the unloading confining pressure is the same as triaxial compression pressure value, the axial and radial strains variations are larger than that of loading conditions. Under the same initial stress conditions, the changing magnitude of stress required for rock failure is less than that of triaxial compressive process. It is shown that the plastic deformation of salt rock is different from hard rock of brittle failure under unloading confining pressure. The conclusion can be useful in underground gas storage engineering stability analysis and gas injection/extraction process.

Based on uniaxial compression tests on gypsum specimens, a series of digital images of materials are obtained during the process from damage to failure. According to the gray correlation coefficient of the digital image, the damage magnitude is built to reflect damage evolution of the material. A series of binary images of the damage evolution are obtained by image processing. The fractal and multifractal spectrum theories are adopted to describe the damage evolution on material surface. The results show that the spatial and temporal corresponding relations exist between the distribution evolution of gray correlation coefficient and the localization of surface deformation. With the increase of damage on specimen surface, the relationship between fractal dimension and strain is linear; the curve of multifractal spectrum changes from symmetric single-peak form to left concentrated form and the spectral width decreases.

The shear behavior of joints was not easy to predict under constant normal stiffness (CNS) conditions. The normal compressive stress would increase during shearing when the joints dilation took place. Meanwhile the increasing of compressive stress would cause the restriction of dilation, which would finally reduce the increment of compressive stress. A simple model was presented to simulate the joints shear behavior under CNS conditions. It was based on the relationship between normal displacement and shear displacement of the joints in the shearing process, from which the normal compressive stresses in the CNS conditions were calculated iteratively and the shear stresses were obtained finally. The influences of parameters of rock joints on shear behavior under CNS conditions were also discussed. The results show that the shear stresses are determined coordinately by the constant normal stiffness and the normal deformation parameters of joints, including the uniaxial compressive deformation and the decreasing of dilation angle; and the shear stress will reach a high value if the joints are not easy to compress during CNS shearing process.

Based on the similarity theory and the design data of Yangtianqing tailings impoundments of Yuxi Mining Co., Ltd. in Yunnan province, a series of laboratory simulation model experiments of tailings dam-break surges with floating debris in different collapse forms (1/4, 1/2 and the entire instantaneous collapse) were carried out in a uniform geometry flume of College of Resources and Environmental Science. The flow characteristics of slurry from tailings dam-break had be explored in the simulation model experiments. The experimental results show: (1) The collapse gate of tailings dam has an obvious influence on the impact stress, depth and evolution characteristics of slurry from tailings dam-break. (2) The slurry evolution course at the sections of downstream has an obvious attenuation phenomenon, and the slurry flows faster in the front, the depth and the impact stress vary along the long trail. (3) With the collapse gate augmenting, the impact stress and the slurry depth is increased obviously at a same section and the law of increase tendency is nonlinear. (4) The flow pattern of slurry has undergone great changes at the sharp bend flume; the vortex appears at the inner side and the reflection phenomena appear at the outside, the vortex and reflection phenomenon in entire instantaneous collapse condition are greater obviously than which of 1/2 and 1/4 instantaneous dam-break. (5) The time of the front slurry arriving at a same section of downstream in entire instantaneous collapse condition is far less than that of 1/2 and 1/4 instantaneous collapse conditions. With the collapse gate diminishing, the peak of impact stress is weakened and the time that the impact stress gets to the peak value is delayed. The results can provide some references to study of the characteristics of slurry flow in different collapse gates deeply and there is an important real significance to conduct the mine enterprises to take some corresponding actions to prevent and control the disaster of tailings dam-break.

Based on frost heave and frost boil disease mechanism analyses of embankment in permafrost regions, a new synthetical embankment with permeable geotextile, block stone interlayer and waterproof geotextile is proposed, whose anti-frost heave and boil effect is investigated by a model test. The results show that, compared with common embankment, the new synthetical anti-frost heave and boil embankment can decrease its temperature and have good cooling effect whether the air temperature is high or not. Moreover, it can decrease water content effectively; and the decrease ratio of water content is increasing with period increasing. These properties are advantageous to prevent frost heave and boil diseases from occurring and developing. What’s more, the new synthetical anti-frost heave and boil embankment is easily constructed and its cost is also low. Therefore, it has extensive application prospects.

The water pressure equilibrium system of deep tunnel is composed of groundwater, surrounding rock, grouting ring and lining, which can not be systematically investigated by the traditional methods for the stress and plastic zone of tunnel. The elastoplastic solution for deep tunnel is carried out. The surrounding rock, grouting ring and lining are assumed as isotropic continuous elastoplastic medium. Based on the elastoplastic mechanics, groundwater hydraulics theory and Mohr-Coulomb criterion, the calculation formulas for stress and plastic zone of axisymmetric deep tunnel under the combined action of four factors are deduced. To calculate a deep tunnel, Matlab is adopted to edit routine for the computation. Compared with the calculated results obtained from the traditional solutions, the correctness of deduced formulas is validated; and the defects of traditional methods are indicated. The influence of grouting parameters on plastic zone and the method for deciding optimum thickness of grouting ring are also discussed.

Based on the laboratory tests, the fractal characteristics of granularity for loose micaschist were studied by the fractal geometry theory; and the relevance of the fractal dimension with coarse granule and shear strength parameters was discussed. The results show that: (1) the change trend of fractal dimension is inversely related to the coarse granulae, that is the fractal dimension will increase with the decrease of coarse granulae; (2) according to the calculations, when the fractal dimension is in the range of 1.887-2.631 the size distribution grading of loose micaschist is good, which indicated that the fractal dimension can take the place of Cu and Cc to represent the size distribution grading of loose rock materials; (3) there is a better relevance between the value of fractal dimension and internal friction angle under the fine grading, and the functional relation of which is negative exponent, but the regularity is not obvious between the cohesive and the fractal dimension.

Based on similarity theory and considered non-Darcy character in low permeability porous media, the theory about simulation experiments on the oil-water two-phase flows were researched. The dimensionless forms of controlled equations about oil-water two-phase flows were derived by the equation analysis method; and the similarity criterion about the waterflooding simulation experiment in low permeability cores was obtained. The dimensionless controlled equations were solved by the IMPES method; so the numerical simulator including similarity criterion was obtained. Through sensitivity analysis, the influence degree of every similarity criterion on experimental results was calculated and verified by waterflooding experimental results of low permeability cores. Results show that the similarity criterion whose sensitive factor is larger has greater influence on the experimental result. Contrarily, it has little influence on the experimental result. Therefore, when the physical model is designed and not all similarity criterions between the prototype and the model are equal, the larger similarity criterion should be given priority to be equal.

A model test was performed to study the failure progress of natural and reinforced slopes by a model box with the size of 1 m×2 m×4 m. The tests included three different grade angles of slope (30°, 45° and 60°) and two patterns of slope surface (flat and convex). The failure of slope was induced by tilting the model box and the failure progress was recorded with digital camera. The crack propagation, form of landslide mass and gradient angle of the box were summarized and analyzed. The results show that the form of slope failure is three dimensional and depends on the grade angles and patterns of slope; given the same grade angle, the flat is more stable than the convex but almost same in crack location; the reinforced slope is more stable and has a different failure form. The study results are useful to understand better the progress and form of slope failure, and provide a scientific base for treatment of landslide.

Lateral stress relaxation is one of the important rheological characteristics of soil under confined compression condition. Confined rheological tests are carried out on the revamped consolidation apparatus. The results show that the lateral stress relaxation curves and the vertical creep curves of soil appear synchronous process which consists of unsteady, steady and sudden change stages under confined compression with constant load. Then the mechanism of lateral stress relaxation is analyzed based on the test curves by using the theory of structural grain directional array and the strength theory of soil. Some conclusions can be achieved through mechanism analysis that the three stages relaxation characteristics of lateral stress are induced by the interaction between compaction recovery and shear fracture of soil structure; and the limit state of lateral stress in stable relaxation stage is controlled by the shear strength of soil. In addition, the relaxation extent of lateral stress in higher stress level is more remarkable than in lower stress level. These conclusions will be favorable for further study of the relation between long-term bearing capacity and settlement of ground.

Uniaxial unconfined compressive strength tests are conducted on Shanghai frozen clay which have three different water contents. Through the analysis of experimental results, the compressive strength of frozen clay is affected by temperature, loading rate, water content and dry density. Test results show that the lower the temperature and the greater the loading rate, the higher the compressive strength of frozen clay. The parameters of exponential function model concerning compressive strength and temperature as well as the parameters of power function model concerning compressive strength and loading rate are deduced. It is also established the equation of compressive strength based on the variables of temperature, loading rate and water content (or dry density). By orthogonal analysis, the influences of each factor on compressive strength of frozen clay are in the following descending order: temperature, loading rate and water content.

It’s found that the compression of pile shares a high proportion of the overall settlement in overlength pile foundation. Assuming the pile foundation as a rigid body in the equivalent pier method is not appropriate. A method considering compressibility of pile is proposed to calculate the settlement of super-long pile foundation. By analyzing the existing test data of overlength piles, a fitting equation expressed by compressibility coefficient of rock-socketed pile shaft is given; and a coefficient of 0.5 for non-rock- socketed pile is obtained. The formulas for settling ratios of pile shaft and pile tip are deduced. Meanwhile, the Matlab program is realized. At last, considering compressibility of pile, a case study is presented to calculate the settlement of overlength pile foundation; and the calculated and measured results have good agreement.

Initial geostress field is a basic index for underground engineering design. According to geological data of Jiangbian hydropower station diversion tunnel area, a numerical model of this area is established by fast Lagrangian analysis of continua in three dimensions (FLAC3D). The mixed boundary conditions and lateral pressure coefficients which change with depth are applied to simulate different kinds of rocks, fault fracture zone and alteration zone along the diversion tunnel, so as to conduct positive analysis. According to the measured principal stress data of the engineering site, based on the principle of radial basis function (RBF) neural network, back analyses of rock mechanical parameters and initial stress field are made. The calculated results are consistent well with the measured results and meet accuracy requirements. The results show that the back analysis results are in line with the actual project; and back analysis method is reasonable.

The deformation and stability of gentle anti-dip red sandstone slope in Hubei section of Shanghai-Chongqing Expressway is investigated. The high-steep slope in gentle anti-dip red sandstone is easy to soften and collapse. The unloading deformation of high-steep slope resulted from natural erosion can be dozens of millimetres to nearly 100 millimetres. The direction of unloading deformation overlaps with structural joints, which widen the joint fissure and increase the connectivity and finally provide a steep downslope failure surface for the high-steep slope. The unloading and softening deformations of highway cutting slope further increase the slope deformation and decrease slope stability; and the deformation modulus can decrease by 80%. Groundwater flows into unloading fissures and causes a certain height of hydrostatic pressure. Rock mass strength is significantly decreased by the softening effect of groundwater and the softening coefficient of rock block generally is about 0.3-0.7. Under 30-40 m hydrostatic pressure, the stability coefficient of slope decreases from 5.56 to 1.96 before excavation and from 2.77 to 1.07 after excavation. All of these adverse effects decrease the stability of anti-dip slope and even cause failure. It is concluded that reinforcements should be installed immediately after the slope cutting and measures should be taken to prevent the accumulation of groundwater in the unloading fissures, so as to reduce softening of slope.

Generally, for some advanced open metal mines, the combined mining of open-pit and underground is adopted to extend the life of open pit mine or tide over interim of open-pit to underground, which makes the issues of the slope stability under underground mining highlighted. The slope factor of stability (FOS) solved by limit equilibrium method (LEM) is a constant value with the same geometric shape, upper load and material properties etc. of the slope, so it can not reflect the influence of underground mining on slope stability. The vector sum method which based on stress field can overcome the above shortcoming is used to solve the FOS of slip face; meanwhile, the searching of critical slip surface before and after mining is done by combined method of genetic algorithm and ant colony algorithm. Finally, an assumed example and two engineering cases are given to show the methods’ effectiveness of solving the FOS and searching the critical slip surface, as well as to indicate the variation of the open-mining slope under underground mining.

Random-fuzzy statistical method can be used to reflect the space variation of geotechnical parameters. The method for determining the weight coefficient is discussed. Especially, the significance of “reference point” is studied. The results show that when the reference point limitlessly approaches the core point, the corresponding maximum membership degree is just the desired correct result. Based on the principle of random-fuzzy statistical method, an iterative calculation procedure is proposed to calculate the objective function. To analyze the geotechnical parameters in a certain nuclear power plant project, the curves of membership degree of each rock sample against reference point, as well as the procedure curves of reference point approaching core point, are obtained. The results show that the exponential function well expresses the function of membership degree. The distribution of membership degrees of samples exhibits normal distribution of narrow region. Therefore, the random-fuzzy statistical method is consistent with the practice; and then it is better than the conventional random method.

In order to explore the large deformation mechanism and control method of deep soft roadway, analysis is made based on the engineering background of level -885 m east wing rail roadway of Zhuji Coal Mine, Huainan mining area. This roadway is a typical deep soft rock of high geostress, of which the surrounding rock becomes extremely unstable, showing strong nonlinear deformation characteristics and high deformation rate after excavation. Rating of the large deformation is firstly made. The surrounding rock stress field and displacement field are analyzed by Hoek-Brown elastoplastic constitutive model. Considering the strength of surrounding rock, the influences of disturbance, the cross-section shape, the roadway deformation mechanism are revealed finally. Optimized supporting method is proposed which is paid great attention to the floor supporting and bottom shearing support. Numerical simulation and field monitoring show that the new method obtained good effect and it’s a kind of effective method to controlling large deformation of surrounding rocks of deep roadway.

For great destructive debris flow, predicting the likelihood of its early warning is an important means of disaster prevention and mitigation, as well as scholars focus on the key issues. Based on the principle of efficacy coefficient method, analyzing the meteorological and geological environmental factors synthetically; evaluation factors such as hill slope, relative height, vegetation cover, along the groove loose material reserves, 5 d cumulative rainfall, maximum rainfall intensity per hour, and intraday rainfall are selected. Using the improved analytic hierarchy process to calculate the weight coefficients of evaluation factors, a early warning of debris flow prediction model is established. Taking an early warning of debris flow in Xiuyan for example, the model is tested to predict the results which reflect the actual situation better. The debris flow early warning model has higher reliability and practicability, and it can provide new ideas and methods for early warning of debris flow prediction.

According to the construction conditions of Kuiqi No.2 small-space tunnel with super-large cross-section and eight traffic lanes in the second phase project of Fuzhou International Airport Highway, a discrete element analysis program is established to simulate the construction process. In the program, the double-heading construction method, CRD method and CD method have been simulated. The settlements of vault, horizontal deformations of middle rock pillar, horizontal deformations of surrounding rock and plastic zone of surrounding rock are analyzed and the advantages of the three methods are compared. Considering the characteristics of Kuiqi No.2 Tunnel, the practical construction scheme is optimized. The double-heading method is changed to CRD method at the tunnel entrance. The modification of construction method has great contribution to cut down the cost and to reduce erection time. The results provide some reasonable references to design and construction for similar engineering.

Landslide deformation prediction has significant practical value that can give the guide for preventing the disaster and protecting the people’s life and property safety. Form the point of system theory, the displacement time-series can be divided into trend item and deviate item. Combined with rheological theory of rock and soil and principle of time-series, these two items can be researched based on deep research of main environmental variables that have obvious influences on landslide deformation. The trend item of displacement time-series can be extracted by grey system model. Evolutionary neural network, constructed by combining genetic algorithm and artificial neural network, can be used to construct the nonlinear relationship between main environmental variables and deviate item. According to creep stage and deformation response to the environmental variables, the comprehensive model must be changed in real time. So the dynamic gray model-evolutionary neural network prediction model of landslide deformation can be constructed by this train of thought. Applying this thinking and method into research of some landslides in the Three Gorges reservoir area, the validity and practical value of this model can be demonstrated. And it also shows that the dynamic prediction of landslide deformation is very crucial.

Huangtupo landslide is studied in detail as a typical example in the Three Gorges reservoir area. Combined with the monitoring data of the groundwater table of the landslide, the impact of reservoir water level variation on groundwater table of the landslide is studied. A finite element computational model of Huangtupo landslide is established for seepage analysis; and the reasonable boundary condition of the model is defined. The transient seepage field of Huangtupo landslide under water level variation is computed using SEEP/W program of Geo-Studio analysis software. Moreover, the dynamic variation of the phreatic line is also analyzed. It is found that the impact area of water level variation on phreatic line is within the range of 300m in the front of the landslide. The location of phreatic line in the front of the landslide is predicted when water level rises and decreases. The stability affected by the phreatic line changing in reservoir bank landslide under water level variation is analyzed. This paper offers a useful reference for the study of phreatic line and stability analysis of reservoir bank landslide.

Standard drillability test is carried out at atmosphere pressure without considering the effect of confining pressures. The test results mainly reflect the intrinsic characters of rock. Downhole rock is under different stresses and these stresses influence the rock drillability a lot. Based on analysis of rock drillability test, the invasion depth of tooth is an important influential factor on rock drillability. A model for calculation invasion depth is presented considering both rock features and confining pressures, based on Mohr-Coulomb strength criterion. Through comparing rock drillability tested with invasion depth calculation, a close relationship can be built between invasion depth and drillability. Since the invasion depth formula includes the influences of rock features and confining pressures, the rock drillabilty under real drilling condition can be predicted by calculating invasion depth.

To better understand the effect of facing rigidity on the deformation and failure of reinforced-sand retaining wall, a series of results obtained from the laboratory model tests with different facing rigidities, are simulated by a nonlinear FEM incorporating an elastoplastic constitutive model for sand. The constitutive model has been developed based on the modified plastic strain energy concept, which can simulate the effect of stress path accurately. By the comparisons between the numerical and experimental results, it is found that the load-settlement relationships of the reinforced-sand walls and the effects of facing rigidity on the bearing capacity and deformation and failure of reinfroced-sand retaining walls obtained by the presented FEM agree well with those from the physical experiment. With the increase of facing rigidity, the inhibition of facing on the shear bands increases and the peak bearing capacity of reinforced-sand retaining walls are also improved due to the increase of the sand strength σ1 induced by the increase of the confining pressure σ3 of sand.

Lots of shallow landslides in residual soil slopes are triggered by rainfall every year in Southeastern coastal area of China. Prediction of the rainfall-induced landslides is a hot research topic. Rainfall intensity-duration curve(I-D curve for short) is used commonly by previous researches to predict the landslide induced by rainfall. Firstly, the geological conditions of residual soil slopes and climate condition in Southeastern coastal areas of China are presented. Then the cross-sections and engineering properties of the residual soil slopes are presented. A finite element software, Geo-Studio, is used to study the effects of the initial moisture condition, shear strength, saturated permeability coefficient, slope angle, thickness of residual soil layer and rainfall pattern on I-D curve. Results from the parametric analyses show that shear strength, slope angle, saturated permeability coefficient and rainfall pattern influence the I-D curve significantly. With a decrease in shear strength, an increase in saturated permeability coefficient or an increase in slope angle, the rainfall duration causing a slope failure shows a decreasing trend. The influence of initial moisture condition on I-D curve is significant when rainfall intensity is lower. When rainfall intensity is larger than saturated permeability coefficient of the residual soil layer, the infiltration capacity is controlled by permeability coefficient; the rainfall duration causing a slope failure doesn’t change with the increasing of rainfall intensity. The research results can provide a basis for the application of I-D curve to predicting rainfall-induced landslides in residual soil slope in Southeastern coastal areas of China.

As a new light-retaining structure, the reinforced earth retaining wall has been widely used in roads, railways and ports. And with the rapid development of the technology of reinforced earth retaining wall, the types of facing are also more and more abundant. A two-dimensional (2D) finite element analysis is conducted to simulate a reinforced earth retaining wall for embankment by using the finite element software Plaxis. To investigate the influence of different facing types on the mechanical behavior of the reinforced earth retaining wall for embankment, the calculated results of reinforced earth retaining wall with three facing types (wrapped facing, overall facing and assembled facing) are analyzed, including the lateral earth pressure, the vertical earth pressure, the lateral deformation of retaining wall, the strain of reinforcement, and the factor of stability. It is found that the numerical results of vertical and lateral earth pressures are less than theoretical results. The reinforced earth retaining wall with the wrapped facing has a larger strain than those with the other two facing types. Furthermore, the three facing types have little influence on the overall stability of reinforced earth retaining wall. These results provide theoretical guidance for engineering application.

The pile-soil interactions are constrained by the pile cap in pile groups with cap, while mutually independent in pile groups without cap. The mechanism of negative skin friction variation in pile groups with cap is analyzed briefly. Under the condition of groundwater level falling, the negative skin friction behaviors of pile groups with cap are analyzed by three-dimensional finite element method. The analytical results show that the negative skin friction of pile groups with cap is generally similar to that of a single pile: as the loads on cap increasing, the neutral point moves up, additional settlement increases and the downdrag decreases, though there are differences between piles in different positions. The constraints of settlement of piles in various positions by the cap are significant when the load is not large; so that the neutral point of piles are almost coincident. As the load increasing, the deformation of the cap increases and the neutral points of piles become more various, lowest for the corner pile, second for the perimeter pile and highest for the center pile. The negative skin friction of each pile in pile groups with cap mobilizes differently along the depth. It is mobilized most fully for the corner pile, second for the perimeter pile and least for the center pile.

Based on Biot’s wave theory, dynamic response of a circular lining tunnel in a saturated poroelastic soil due to a moving ring load is investigated. The liner is modeled as an elastic body and the soil is modeled as saturated porous medium. In order to uncoupling governing equations, two scalar potentials are introduced to represent the displacement for the solid skeleton, the pore fluid and the linner. According to boundary condition and continuity condition, the analytical solutions of dynamic response, such as stress, displacement and water pressure, are derived in frequency and wave-number domain by using Fourier transformation. Numerical results are obtained by inverse Fourier transformation. To compare the results, dynamic response of three tunnel models (tunnel in elasticity, tunnel in saturated soil and lining tunnel in saturated soil) is calculated. The results of numerical example show: (1) the velocity of the moving load greatly influences dynamic response of three tunnel models; (2) large difference between the tunnel in elasticity and tunnel in saturated soil, so the soil near the tunnel should be modeled as saturated porous medium in abundant water field; (3)the influence of the liner on the dynamic response of the tunnel is remarkable; so the liner effect must be considered in the dynamic analysis of the tunnel.

The problem of dynamic stress concentration around a shallow cylindrical cavity incident by steady-state shear horizontal SH wave in an anisotropically elastic half-space ware solved; and the rules that anisotropy of the medium influenced dynamic stress concentration around the cavity were investigated. By using the function of complex variable and multi-polar coordinate system, we constructed scattering wave function of the cylindrical cavity, which automatically satisfied the zero-stress boundary condition on the horizontal surface in elastic half-space and the Sommerfeld radiation condition at infinity. According to zero-stress boundary condition of the cylindrical cavity, we solved coefficients of the scattering wave function by least square method. Finally, the effects of different media characteristics, wave numbers, and embedded depth on dynamic stress concentration factors around the cylindrical cavity were analyzed, when SH wave incident with different angles. Numerical results show that: the dynamic stress concentration factor around cylindrical cavity increases obviously in anisotropically elastic half-space in contrast with isotropic one.

The method of soft soil subgrade reinforcement with chemical churning pile is used more and more in projects of subgrade treatment. At present, the researches about chemical churning pile usually focus on improvement in construction techniques or bearing characteristics of single pile. But research about bearing characteristics of chemical churning pile groups is not much. Based on MIDAS-GTS three-dimensional finite element analysis, the influence of design parameters on bearing characteristics of chemical churning pile groups is studied. These design parameters of chemical churning pile include layout, elastic modulus, length, diameter of piles, and distance between piles, the parameters of interface between piles and soil. The results show that the vertical settlement of soil within the range between surface and pile bottom is reduced in soft soil subgrade reinforced by chemical churning piles; but the method has little effect on the vertical settlement of soil under pile bottom. Larger pile diameter and higher material strength can improve the bearing capacity of composite subgrade. But different layouts of chemical churning piles and whether to set up Goodman interface element have little influence on bearing capacity of composite subgrade.

Foam in porous media can plug some pore channels and reduce gas mobility. Direct observation of foam flow patterns in porous media is difficult and therefore research on relationships between gas mobility and bubble size is scarce. The influence of bubble size on fluid resistance in porous media is simulated using the Navier-Stokes equation combined with the conservative level set method. The computational results reveal that the effect of bubble size on flow resistance is pronounced. The pore wall cannot constrain bubble deformation when size of the bubble is smaller than that of the pore throat. In that case, the flow resistance is steady in the flow and is the same as resistance of the single-phase liquid flow. Therefore, small bubbles cannot plug pore channels. The pore channel constrains bubble deformation when size of the bubble is larger than that of the pore throat; and the flow resistance is fluctuant in the flow. The maximum resistance increases linearly with the increase of bubble volume. When the flow resistance reaches the maximum, it decreases linearly with the increase of bubble volume. Alternation of the increase and decrease of the maximum resistance is periodic; and the period is unit pore-body volume.

Engineering regional geologic condition is an important factor that affects the stabilization of underground cavern group, while the common numerical analysis soft wares have some disadvantages such as the long time consumption for modeling, low accuracy and the difficulty in reflecting the real complex geological features. Aiming at these problems, a mixed data structure， in which nonuniform rational B-spline(NURBS) is predominated，is used to carry out the 3D detailed modeling of the complex regional geological structure; and the whole 3D refined geological model of a large underground cavern group in Southwest China is established by this method. Based on this geological model, a numerical model including complex geological factors such as the space surface faults, formations have also been built; and combine the implicit and explicit module of ABAQUS, the underground cavern group excavation and dynamic response under seismic load have been simulated. The results indicate that: This approach not only reflects the actual geological condition to the greatest degree, but also makes against the mesh generation and numerical calculation; thus it provides an accurate and practical model for the dynamic response analysis of underground cavern group and important technical support for the seismic safety evaluation of underground cavern group.

In order to evaluate the deformation control mechanism of shield tail void grouting, the influence of cementation on consolidation process of cemented mortar is studied by the self-made experimental apparatus of consolidation deformation. On this basis, consolidation deformation model of cemented mortar is built, which can reflect the influence of cementation. The numerical calculation program is made, which is verified by experimental results. The numerical calculation model of cemented mortar consolidation deformation will play an important role to improve the simulation accuracy of shield tunnel construction.

Aiming at the simulation problems on the inner anchoring section of prestressed anchor cable, composite element model is presented, which provides a new idea to solve this problem. The most remarkable feature of the model is that it not only can describe steel strand wire, mortar, interfaces and other detailed structures, but also simplify calculation mesh. Elaborate simulation is conducted in order to verify the new method. Steel strand wire, mortar, interfaces and other structures are discretized in detail. The results show that the axial displacement and stress are exponential decreasing along the steel strand wire from outside to inside. The longer inner anchoring section is not better for anchoring effect, but it is more suitable for 3-5 m. These are proved by field monitoring. Numerical example is carried out to display the validity and rationality of the method.

Based on a comprehensive study of existing data of hydropower projects and the features of radial basis function (RBF) interpolation, a model for three-dimensional strata block via interpolation of RBF is built. During the process of blocked interpolation, a weight function in order to keep the continuity at the conjunction of two blocks is adopted. With the formation of the data for each layer, merging these data between layers and adding fault information, a three-dimensional strata model is obtained finally. Taking Xiaowan Hydropower Project for example, a corresponding model through the method of blocked interpolation of RBF is built; and access to any section is provided. Finally, the correctness and feasibility of grid blocked strata modelling are verified.

A three dimensional nonlinear finite element model of pile group foundation of a high-speed railway bridge was built. Combined with the corresponding data obtained from field tests, the rules of pile axial force, pile side friction force, soil additional stress, pore water pressure distribution, excess pore water pressure dissipation and settlement of pile group foundation were analyzed. The calculation results show that the axial forces of corner piles are larger than the side piles which are larger than the center piles; and the axial forces of corner piles and side piles reduce greatly along the pile body; and the axial forces of center piles decrease slowly. Moreover, the regular pattern of pile side friction is that the pile side friction measurement of corner piles are larger than the side piles which are larger than the center piles generally; and the amount of relative displacement between pile and soil is bigger on the upper and less on the lower. That is to say, the amount of relative displacement between pile and soil on the upper of pile is larger than on the middle and lower of pile. Furthermore, the soil additional stress and excess pore water pressure generated by external loads mainly concentrate in soil under the pile cap within a certain range; and their attenuation gradients decrease along the depth gradually. With the increasing of the consolidation time, the settlement of pile group foundation arrives to be stabilized.

Through borehole drilled in the top rock, the bore observing system by bore resistivity method is formed; and the distortion and collapsing characters in the top rock of the working face can be tested dynamically during digging process. According to mining velocity the changing characters of electric field in different times can be gained. And the changing law of overburden failure affected by mining can be researched comprehensively. Limited by testing condition in the spot of laneway, through single borehole in the top rock the testing data have the full space effect, the explaining result and location for rock failure is affected in different extents. Its resolution for the law of overburden failure is decreased. Through model test and practical detection, the resistivity testing method using the single borehole in the top rock is improved. The bore-laneway resistivity method is formed through laying the poles in the laneway, and the binding character of the resistivity data is enhanced compared to the single borehole system in the top rock. It provides the base for the resistivity inversion and the height judgment of the two belts. The practical researching results show that the bore-laneway resistivity CT method has sensitive reaction to structure change affected by mining; and its resistivity section is clear and dynamic. The resistivity ratio section and background detection can resolve effectively the characters of the process in the coal mining. The explaining capable of the detection achievements for the overburden failure is improved. The result is helpful to renew the practice of the overburden failure.

Stress history of soft soil analyzed by in-situ test technology can avoid the structural disturbance of soils during sampling and laboratory experiments, and better reflect their real property. Traditional overconsolidation ratio (OCR) calculation methods of cone penetration test with pore pressure measurement (CPTU) technology are mainly based on overconsolidated soils and lack consideration of those soils under the condition of underconsolidated state. Therefore, it shows certain limitations in practical application. Based on literature review, a consolidation state evaluation method is introduced in detail. First, the in-situ initial pore pressure is deduced through final part of the incomplete pore pressure dissipation test curve together with the extrapolation method of inverse time square root of time. It means that there exists inherent pore pressure if the initial pore pressure is greater than hydrostatic pressure; and the soil is underconsolidated. Then, the degree of underconsolidation of soft soil can be quantitatively evaluated by calculating the parameter of consolidation state. Engineering application indicates that the method is not only reasonable but feasible, and can be widely used without limitation of soil property and region. The method can effectively determine the consolidation degree of soft soil without any laboratory consolidation test. The research achievement is instructive for reasonable engineering property assessment of underconsolidated soft soils.