In order to study the soil-water characteristic curve (SWCC) of Guilin lateritic clay in full suction range, three suction control or measurement methods are used: the pressure plate method, filter paper method and saturated salt solution method. Some tests are performed to study the influence of dry density on the SWCC. The result shows that the air entry value of compacted Guilin lateritic clay with dry density of 1.4 g/cm3 is about 20 kPa. The SWCC of Guilin lateritic clay is different from the typical SWCC. In the transition zone, there are three lines with different slopes and the slope of middle segment is small. When the suction increases to 367 MPa, the water content of the soil is only 0.74% .It can be inferred that the water content and saturation degree will decrease to zero if the suction increases to 106 kPa. When the SWCC is expressed by the relation between suction and water content, the SWCCs with different dry densities coincide with each other in the high suction range, that means that the dry density has no influence on the SWCC. When the SWCC is expressed by the relation between suction and saturation degree, the SWCC with high dry density is higher than the smaller one in the lower suction range. When the suction is high, the SWCCs with different dry densities coincide with each other.

Expansive soil will appear volume expansion under moisture adsorption condition. It is very important to study the soil-water characteristics of expansive soil under moisture adsorption and expansive conditions. Considering nine Hebei expansive soils as the study objects, soil-water characteristic curve (SWCC) tests by osmotic method and filter paper method are carried out. Filter paper method is used to measure the lower suction range, while osmotic method is used to measure the higher suction range. Moisture adsorption tests are carried out by steam humidification method. Based on soil-water characteristics tests and moisture adsorption tests, the volume change rules of expansive soils under wetting condition can be obtained. The experiment data are then curve fitting by using Matlab, and the gravity water content-suction curves (w-ψ curves) and the volumetric water content-suction curves (θw3-ψ curves) are obtained. The influence of the volume change of expansive soil under moisture adsorption condition on the θw3-ψ curves is analyzed; and the variability and correlation between curve fitting parameters of w-ψ curves and θw3-ψ curves are also studied. The results show that the steam humidification method is a good approach for moisture adsorption test. During the steam humidification process, the moisture is adsorbed slowly and uniformly, and the shape of soil sample remains unchanged. The void ratio?gravity water content curve can be divided into four stages, which are initial stage, approximate linear stage, nearly horizontal stage, and ascent stage along the saturation line. The difference between the two types of SWCCs (w-ψ curves and θw3-ψ curves) is due to the volume change of expansive soil samples during the wetting process, and the extent of volume change depends heavily on the water content of expansive soil samples after the moisture adsorption process. The variability of w-ψ curves is less than that of θw3-ψ curves. For both of the two types of SWCCs, the variability of parameter n is relatively small, which means that the slopes of SWCCs are close to each other for different soils. The variabilites of parameters a and m are larger than that of parameter n. The corresponding curve fitting parameters of w-ψ curves and θw3-ψ curves are linearly correlated. Therefore, the curve fitting parameters of θw3-ψ curves can be preliminary estimated by those of w-ψ curves.

In Northwest China, the climate is mainly arid and semiarid and loess is widely distributed. This paper firstly presents the climate characteristics of three representative cities in Northwest China for nearly 50 years and the water storage capacities of the three types of loess. The water balance method proposed by Chen，Khire et al is used to evaluate the feasibility of using loess as soil cover material, and then the design thickness of monolithic loess soil cover is determined. The analyses demonstrate that: in Northwest China, hot rainy and the lush vegetation in summer compared with cold dry and the withered vegetation in winter , the intensities of precipitation and evapotranspiration have good synchronization, which is just application for soil cover. When the loess is used as soil cover material in the Northwest China, the design thickness of monolithic soil cover ranges from 0.54 to 1.92 m. The design thickness depends on the climate condition and the type of loess. From arid, semiarid to semihumid regions, the thickness becomes larger. For a given region, the design thickness for the silty loess is the least, and that for the sandy loess is the largest. The use of loess as soil cover material for landfills in Northwest China has advantages with respect to both technical and economical aspects. It is deserved to put the technique into engineering practice and call for more research.

For researching the self-property of yielding anchor cable in the high slope supported, and getting first-hand data of yielding support, the article taking the high slope located in Hongping power plant in Jiangxi province as engineering background, and using a new yielding anchor cable which is produced by Tuqiang Engineering Materials Co., Ltd., field experiments on different length of free section and yielding anchor cable are conducted. Then reveals: Part of the appeared obvious yielding slippage; yielding effect is significant. But the pressure value is great different between tension of orifice and the design of yielding support. It indicated that orifices tension is not as ideal all passed to the anchor cable inside the hole; instead a large part of the orifice tension will be used to overcome the fritional resistance between the anchor cable and anchor hole, And quantity has reached the degree of which is not allowed to ignore. At the same time, test reveals that the length of anchor and free section, number of beam and anchor hole construction quality play a crucial influence on the value of the friction resistance; the longer anchor cable and free section, the more number of beam, the worse the construction quality are , the larger frictional resistance is. And then design focus and further research contents about slope protection by anchor cable in future are put forward.

Hong Kong-Zhuhai-Macao Bridge Gongbei tunnel is located in coastal areas. Its groundwater is connected to the seawater, foundation pit bottom of Gongbei tunnel is reinforced by dry jet mixing method and high pressure jet grouting method. Under the action of corrosive ions in seawater, strength and stability of cemented soil produced by reinforcement would get changed; thus impact on engineering safety. According to difference between the two kinds of construction technology，two kinds of cemented soil test blocks which contain or not contain corrosive substance were made, one-component chemical solutions of different concentrations were prepared to model water erosion environment, then the prepared cemented soil test samples were put into the corrosive solution to soak for scheduled short period (≤28 d). By unconfined compression test, SEM and ion chromatography test, change laws of microstructure and unconfined compression strength of cemented soil test samples with corrosion time and solution concentration after short period soaking in one-component erosion solution; change law of ion concentration in corrosion solution with corrosion time was obtained respectively. Based on chemical component of brine, two-component chemical solutions of different concentrations were prepared to model water erosion environment; then the prepared containing corrosive substances mucky cemented soil test samples were put into the corrosive solutions to soak for scheduled long period(≥90 d). By unconfined compression test, change laws of unconfined compression strength of cemented soil test samples with corrosion time and solution concentration after long period soaking in two-component erosion solutions were obtained. These offer reference frame for temporary and long-lasting cemented soil engineering design and safety maintenance.

In order to reveal the degree and rule that the soluble salt influences the loess thixotropy, taking Ningxia Tongxin loess as the object and its dry density, water content and salinity as factors, the thixotropy of loess is studied by designing the orthogonal test scheme. The results show that thixotropic parameter of loess increases with the growth of the dry density and salinity, and decreases with the growth of the water content and increase with the growth of the age. The sequence of various factors is water content, dry density and salinity, which affect the loess thixotropy. Based on the orthogonal test results, single factor experiment is carried out with the salinity as the factor. It is found that there is a logarithm relationship between thixotropic parameter and salinity; and there is a good correlation between them. It is obvious that the soluble salt affects on the loess thixotropy, the soluble salt is one of the important factors. The conclusion will have important guiding significance on the foundation design, construction and treatment in the loess area.

According to the anti-pullout anchor experimental data, the dynamic broken line model that the anchorage load transfer properties changing with the depth is presented. Firstly, the anti-pullout anchor experiment, including the main parameters and test data, is briefly introduced. Based on that, anchorage load transfer curves of different depths are analyzed and dynamic broken line used for fitting calculation is proposed. Then, by using dynamic broken line model and anchorage axial force and displacement energy method formulas, a matching computation of test data is carried out. The results show that the calculation results coincide with the experimental data. It vindicates that using the dynamic broken line model in fitting calculation is reasonable. At last, applicable conditions and the supplementary role of the dynamic broken line model in test research and engineering design are discussed. The distribution of different depth strata geostresses is considered by the dynamic broken line model. Geostress is not directly involved in the calculation, but because of its parameter setting based on the test and relatively simple iterative calculation; the method provides a feasible reference to compute the anchor bearing capacity more sophisticated.

Mononobe-Okabe theory is a widely used method to calculate seismic earth pressure at present; but some hypotheses of which have certain limitations. In light of the deficiency of Mononobe-Okabe theory, and considering the effect of retaining wall deflection on earth pressure, the diagonal slice method is used to deduce the strength distribution of seismic cohesive earth pressure under complex states; earth pressure resultant and its action point. The analytical solution of critical rupture angle is given with graphical method. Research results show that fill cohesion and seismic coefficient influence earth pressure signally; ignoring the surface cracking of cohesive fill and the impact of the earthquake on the uniform overload and the crack fill equivalent overload would make the result of active earth pressure turn small, whose deviation would turn big as fill cohesion and uniform overload goes up; earth pressure is in linear distribution along the height of wall in different horizontal seismic coefficients; the given formula fits wider situations, and effectively improves the Mononobe-Okabe theory.

Taking RMT-150C rock mechanics testing system developed by Institute of Rock and Soil Mechanics，Chinese Academy of Sciences as the main test platform, five aspects of sandstone in the 96 kN peak with different frequencies and wave loadings in Yichang are studied：relationship between vertical force change rate and time, relationship between vertical deformation rate and time, relationship between apparent elastic modulus and time, relationship between the lateral deformation rate and time, relationship between instantaneous Poisson's ratio and time. Influence of different frequencies and waveforms on the relationships above is drawn.On the basis of putting forward the linear relationship between the non-lag period of apparent tangent modulus and vertical force，calculation formulas and parameters of the triangular wave and sine wave are obtained in different frequencies. The comparison of the calculation and measured values shows that the proposed calculation formulas can be well fitted with the changes rule with milliseconds of the deformation rate of different waveforms and different frequencies. On this basis, the paper gives the triangle and sine wave energy calculation methods, and comparative analysis shows that the listed computing formula and method can make accurate prediction of millisecond on the triangle and sine wave at different frequencies and energy value of different loading rates.

Sufficient experimental evidence shows that a soil cannot reach the fully saturated condition during wetting process, even the matric suction decreases to 0 kPa, and small amount of air is trapped in the pores, rendering the soil to be more compressible than expected in the early beginning of compression process. At this state, the behavior of the soil is different from that of its saturated counterpart. On the other hand, existing coupling constitutive models of unsaturated soils would predict that the soil becomes fully saturated, which is inconsistent with experimental results. Considering the air entrapment effect, a constitutive model with coupling capillary hysteresis and plastic deformation is modified. Comparison of the simulated results and experimental data illustrates that the new model can effectively address the effect of air entrapment on the behavior of unsaturated soils.

The deformation failure and energy dissipation of backfill body are closely relative to confining pressure. Experiments are taken to investigate backfill body samples under uniaxial compression and triaxial compression. Based on the experimental results, the internal relations among deformation feature, failure mode, energy dissipation and confining pressure are studied and compared. The results show that the peak strain of backfill body increases with the increase of the confining pressure, and takes a linear correlation. Under a low confining pressure, backfill body has a brittle failure characteristic and presents a strain softening behavior; as the confining pressure increases, the mechanical feature of backfill body performs by a way of transformation from brittleness to strain hardening; the cement/tailing ratio and solid concentration are higher, the critical value of the confining pressure from brittle to ductile is greater. The forms of crack and fracture propagation are diverse, which can be sorted into single type, parallel type, intersection type and complex type. The main macrofailure modes are X-shaped and Y-shaped shear failure. The forms of failure plane are classified by linear smooth friction surface, arc rough friction surface, linear rough friction surface, terrace rough friction surface. The peak strength also increases linearly as the confining pressure increasing. The sensitivity of cohesion to cement/tailing ratio is higher than that of solid concentration. The deformation energy of backfill body at different compressed stages increases to a considerable extent with the increase of confining pressure. The relations of the amount of energy dissipation before yield deformation stage and after yield deformation stage, unit volume strain energy and total energy consumption take a positive proportion of the confining pressures.

The mechanism of creep from the perspective of internal energy is analyzed. Based on the strain energy theory, a creep constitutive model is established by combining the Perzyna viscoplasticity theory and Nishihara model, which can describe the whole process of transient creep, steady state creep, and accelerated creep. The model takes into account the influence of stress state on the accelerated creep, and defines the critical strain energy density to effectively judge the occurrence time of accelerated creep. On the basis of the unified creep constitutive model, a practical simplified creep constitutive model is built by adopting Drucker-Prager yield criterion and associated flow rule; and using the yield stress ratio to reflect the creep strain rate change of accelerated creep, which can predict the accelerated creep and reflect the whole process of the three stages of creep. As the simulation result is basically consistent with the test data, the research results provide a new idea for the study of rock creep fracture process.

For the sake of investigating the accumulative plastic deformation and its influencing factors of silt with different compaction degrees, moisture contents and stress levels under the repeated loading, a series of dynamic triaxial tests is carried out. According to the relation curves between accumulative plastic strain and loading number，the critical dynamic stresses of silt are obtained. The experimental results demonstrate that the critical dynamic stress values of silt rise with the increase of compaction degree ,and in reverse of moisture content.In order to avoid damage of the pavement structure, the stress state of subgrade should be controlled within the boundaries of the critical dynamic stress. In view of this, the test data within the critical dynamic stress is analyzed; and a new accumulative plastic deformation prediction model of subgrade soil is put forward. The model takes into account the influencing factors of stress and loading number. Through regression analysis, a consistency between the predictive results and the experimental data is obtained. It is shown that the model is accurate and credible. The proposed mode can provide parameters for the subgrade accumulative plastic deformation calculation based on mechanics empirical method. For typical cement concrete pavement structure, the accumulative plastic deformation of silty subgrade under different axial loads and axle configurations are obtained; and it can provide ideas for further evaluation of the effect of accumulative plastic deformation on pavement structure.

Based on the modified Biot theory, the effects of grain compressibility, frequency, porosity, fluid viscosity and dynamic permeability on the velocity and attenuation of the three bulk waves (P1, P2, S) in infinite two-phase porous media are studied by numerical calculation, respectively. Numerical results show that: (1) the velocity and attenuation of compressional waves (P1, P2) are variable and approximately linear with grain compressibility, while those of shear wave (S) almost keep constant, and by quantitative comparison, it is found that whether the effect of grain compressibility can be neglected or not depends on the ratio between skeleton bulk modulus and grain bulk modulus . (2) The porosity affects the velocity of P1 and S obviously; and it can be predicted that mutual conversion between P1 and P2 when the porosity almost reaches 1.0. (3) Both the fluid viscosity and the dynamic permeability have effects on the velocity and attenuation of P1, P2 and S, but for each of the waves, the variation trends with those two parameters are almost opposite. (4) The velocity and attenuation of the three bulk waves increase with frequency; and among them P2 is affected by frequency most.

With rock sample of coal seam roof as matrix and steel wire as bolt and steel sheet as steel strip, anchored rocks have been experimented by means of three-point-bend. Testing results show that: as the differential properties on compressive and tensile of rock，the speed of tensile strain growth is greater than that of compressive and cracks begin to extend on the lower surface of rock and gradually propagate upward in the bending process. The flexural behavior of bolt anchored specimen has been enhanced, while the mechanical properties of rock are improved in anchorage zone, and a certain amount of tensile stress is shared by steel belt and bolt. The cross section stress distribution of specimen could be divided into three stages in accordance with the failure process. The first is elastic stage. Crack generation and propagation is the second stage. The bearing capacity of rock start to deteriorate, and tensile stress gradually shifts to the steel belt, bearing capacity of anchored increases dramatically because crack propagation of rock is limited. The third is failure stage, bolt lost function, deflection increases while bearing capacity of the specimen tends to be stabled.

A practical algorithm of reliability analysis for slope stability is presented based on response surface method and secondorder reliability method (SORM). Independent random variables in U-space are chosen as basic variables and transformed into correlated non-normal variables in original X-space for computing the performance functions. The response surface is constructed using an iterative algorithm to ensure its accuracy with minimum computational expense. Then, the probability of failure is evaluated using the first order reliability method (FORM) and SORM. The accuracy and efficiency of the proposed method are illustrated for a rock slope with plane failure mechanism, via comparing with Monte Carlo simulations, pure FORM and stochastic response surface method. The influence of correlation among random variables and selection of sampling range around tentative design points on the inferred reliability results are investigated. The parametric sensitivity and physical property of random variables obtained from the reliability analysis are also discussed. The proposed method can be used for reliability analysis of practical slopes and also for reliability-based design of reinforcing structures.

In order to investigate the swelling effect of coal induced by gas adsorption, based on the assumption that the surface energy change caused by gas adsorption is equal to the change in elastic energy of the coal, a theoretical model is developed to describe gas adsorption induced swelling. The formulas of adsorptive expansion stress and strain of coal are derived. The model also is tested by experimental results of gas adsorption induced coal swelling from three aspects, such as low pressure, medium pressure and high pressure. The results show that the model agrees well with experimental data of coal deformation induced by the gas adsorption. It is shown that the model is able to describe the differences in swelling behaviour with respect to gas species and at different levels of gas pressures. It is also shown that the volume of the adsorption gas can be ignored when the effects of gas pressure on coal deformation is considered.

In order to obtain interrelation between anisotropic mechanical characteristics of jointed rock masses and ultrasonic propagation variation, by making the cylinder samples with a precasted joint surface, the ultrasonic test and uniaxial compression test of jointed samples with 7 joint dips are conducted. The results show: (1) The ultrasonic wave velocity test values of jointed samples are discretization and obey the normal distribution. The average of wave velocity is between the intact samples and the gypsum samples, and decreases linearly with increase of joint dip. (2) The joint surface with various joint dips has a great influence on mechanical characteristics of jointed samples, so it has remarkable characteristics of anisotropy in stress-strain curve, deformation, strength and failure modes. (3) There is large difference between the mechanical characteristics of jointed samples and the ultrasonic wave propagation variation, and it will have a great error to determine the mechanical parameters via the ultrasonic wave velocity.

Dynamic compression test has been performed on sandstones subjected to 800℃ based on split Hopkinson pressure bar (SHPB) and high-temperature furnace MTS652.02. We study the dynamic properties of sandstone specimens whose strain rate varies within the range between 17.904 s-1 and 62.600 s-1. The test results show that, after heated to 800 ℃, dynamic stress-strain curves of sandstone can be roughly divided into compaction phase, elastic deformation stage, microcracks evolution stage, crack unstable growth stage, strain softening stage and unload stage. With the increasing strain rate, the dynamic elastic modulus and peak stress of sandstone increase with logarithmic trend, while the peak strain decreases with a logarithmic form. The failure mode of sandstone is mainly typical tensile failure in low strain rate, while the proportion of shear fracture surface gradually increases as the increasing of strain rate; failure mode changes from tensile failure to shear failure. Undergoing 800℃ heat treatment，sandstone failure is gradually severe with the elevated strain rate, and the degree of failure is more significant sensitivity at high strain rates.

Seepage flow is one of the mainly hydraulic conditions for debris flow, different seepage discharges possess various seepage forces and scouring abilities which can induce different scales of debris flow. Through flume experiment, this study measures the pore water pressure by piezometer tube at three cross-sections, records the movement of fine particles and collapse process of coarse particles by high definition camera technology in micro respect, which is used to analyze the soil seepage fail and scouring effect in the process of debris flow formation. On this basis, conducting the experiment on fixing the slope angle of flume device is 7 degree and regulates the constant seepage flow discharge of 120, 170, 265 and 320 ml/s respectively, it analyzes the effect of the flow state on soil particles failure and debris flow initiation under different seepage flow discharges. The results indicate that the migration of fine sand particles and collapse of coarse particles which lead to the rearrangement of the soil structures and enlargement of the pore water pressure, are the important reasons for soil particles failure, initiation and scouring by low soil resistant; with increasing of seepage flow discharge, the flow velocity and pore water pressure increasing rapidly, it attained that the coarse particles fail to move are mainly affected by seepage force and flow scouring. Meanwhile, the movement of the soil particles and water flow shows three different flow states, i. c. presented slightly slide, transitional slide and rapid slide.

The destruction of the rock mass is the compression-shear damage that mainly along the shear failure surface. Granite shear rheological experiment in Bangpu mining area in Tibet was carried out. The shear test curve is analyzed and an improved nonlinear Newton components is introducted based on the Burgers model; and then a modified Burgers shear rheological model has been put forward. The stability of the excavation slope at Bangpu mining area is analyzed for a long time by using the new model's parameters. The results show that, (1) The modified Burgers shear rheological model can fit well the three stages of the rock rheology, especially for the accelerating rheological stage, has a well practicability. (2) The excavation slope's displacement is heightened and the stress is also changed in central steps area when considering the rheological long time effect; support and early warning measures should be strengthened in the area.

Landslide early warning system is an effective tool to reduce the rainfall induced landslide hazard. Warning system against single landslide has a huge potential based on reliable physical mechanism. However, the complicated system usually involves many parameters and algorithms so that it is not widely acknowledged until now. In our study, we constructed a relatively simple landslide technical warning system based on an infinite slope model in the laboratory. The details which include warning idea, calculation of warning time, and information transmission are introduced. Experimental results from physical model validated the performance of this technical warning system under the scenes of different rainfall intensities and the initial water contents. Although the errors caused by soil erosion, and uncertainty of slip surface, and disagreement of initial water content, the technical warning system is still proved to have a reliability in the evaluation of the physical landslide model failure.

High pressure jet grouting can directly reinforce weak soil layers of soft soil foundations. In order to investigate the reinforcing functions of the direct reinforcement of weak soil layers to foundations, a group of model tests of natural foundations on weak soil layers and reinforced foundation is performed in comparison. In order to form reinforced foundation , a group of 3×3 piles is set in the weak soil layers.Test results show that direct reinforcement method of weak soil layers can greatly improve foundational settlement characteristics and bearing capacity. Upon reinforcement , piles are noted for good transfer loads, greatly reducing the compression of weak soil layers. Pile top load increases linearly with the increase of applied loads, and top loads of corner piles are the biggest, that ones of side piles are second, and that ones of center piles are smallest. Upper part of piles are subjected to negative friction, lower part of piles are subjected to positive friction, and the maximum axial force for pile is located 25 cm from the pile top. The average pile-soil stress ratio of reinforced area decreases with load increasing.

Unsaturated hydraulic parameters are very important for calculating rainfall infiltration process and stability of landslides. Double rings infiltration tests are conducted on Huangtupo landslide in Three Gorges reservoir area to obtain the saturated hydraulic conductivities of the shallow soil deposits of the landslide. The water content and matric suction of the shallow soil deposits of the landslide are monitored using real-time monitoring system; and a large amount of data is gotten. The soil-water characteristic curves and their fitting parameters are simulated with the van Genuchten’s three-parameter model for the soil-water characteristic curve. Substituting the saturated hydraulic conductivities and the fitting parameters into van Genuchten’s hydraulic conductivity model yields the hydraulic conductivity function of the shallow soil deposits of Huangtupo landslide under unsaturated condition. Therefore, the hydraulic parameters for calculating stability of Huangtupo landslide under rainfall effect are obtained.

The strong dynamic pressure manifestation on the island fully mechanized caving face largely increases the possibility of rockburst. Two strong dynamic pressure manifestation events of the island fully mechanized caving face are analyzed by making use of microseismic and electromagnetic radiation monitoring. The law of energy accumulation and release in coal, as well as the monitoring data variations of microseismic and electromagnetic radiation, which pre and post rockburst, are obtained. The coal of working face generally has a short energy storage time before the rockburst. The number of microseism events and the total energy of microseism events are few in this period, which is monitored by the microseism system. And at the same time the coal electromagnetic radiation intensity value and the pulse number continually increased during this period. The microseism event silence period of working face as well as coal electromagnetic radiation intensity value and pulse number continual ascension period can be seen as rockburst precursor information. By transforming these precursor information into quantitative early warning parameters and index, the method of working face rockburst multiparameter early warning is proposed. Finally, the engineering practice shows that this method is effective.

Two groups centrifuge tests of pit foundation supporting with scattered row piles are carried out by Tongji University. Combined with three-dimensional finite element numerical simulation, the suitability that the specification method is used to calculate the internal forces and displacement of pit supporting structure with scattered row piles is explored. In addition, a theoretical calculation method of earth pressure of pile considering soil arching effect is proposed. Finally, the calculation model of internal forces and displacement of scattered row piles considering soil arching effect is created. The results show that, for pit supporting structure with scattered row piles when the ratios of pile spacing and pile diameter are 2, 3 and 8, the soil between piles can’t form soil arching effect. In addition , when the ratios are 4-7, the soil arching effect between piles is obvious. The results of pile internal forces and displacement by specification method are larger than the result by centrifuge test. Furthermore, the pile internal forces and displacement of pit supporting structure with scattered row piles calculated by the proposed calculation method are more reasonable.

This study investigates the principles of frequency-size of geological disaster in loess hilly region. Baota district in Yan’an city in Shaanxi province is chosen as the typical geological disaster region in loess plateau. The database of geological disaster in Baota district is built through 3S technology, field survey and remote sensing interpretation. In the view of the holism and in the base of scale distribution analysis and maximum entropy principle, the theory that the parameters of frequency-size such as the length, width and thickness of collapse, landslide and unstable slope accorded with negative exponential distribution is come up for the first time using mathematical statistic method. As a result, a simple and effective formula about frequency- size distribution is put forward. At the end, the formula is verified by the example of Baota district. (1) The results mainly show that the geological disaster of Baota district is mainly middle-scale landslide and collapse; however, large-scale disaster plays important role in the control of total area and volume of collapse. (2) Then this study defines the grade index of volume size for researching size distribution of geological disaster. The results show that the size grade index of landslide, collapse and unstable slope is mainly in (5.5, 6], (4, 4.5] and (5, 5.5], respectively. (3) The frequency-size distribution of collapse, landslide, and the length, width and thickness of unstable slope accord with the exponential relation; furthermore, the curve would not have rollover effect. (4) One of simple methods to solve the frequency-size distribution is to get the square root of area and cube root of volume. The results show that they present negative exponential distribution with a good fitting effect (R2>0.9, P<0.05). Thus the formula plays important role in the prediction of the occurrence frequency of landslide in any size.

Swelling deformation of expansive soil due to moisture absorption often leads to safety problems of engineering. Taking Nanyang mid-expansive soil as research object, the triaxial expansive experiment has been realized by improving the water inlet control system and the measurement of external volumetric strain. And the relationship between the volume expansion rate after sufficient moisture absorption, the final water content and the initial water content, the average principal stress has been obtained through the triaxial expansive test. Experimental results show that the volume expansion rate and final water content in different stress states decrease while the cover load or the average principal stress increases, which has a good linear relationship in semi-logarithmic coordinates. Through theoretical derivation, the unified relationship and expression of expansion models in different stress states are established. And applying the expansion model in the numerical calculation, law of stress field distribution of expansive soil slope considering swelling deformation is analyzed; plastic zone developing character of expansive soil slope with different expansion grades in the condition of sufficient moisture absorption is compared; effect of replacement measures with different treatment thicknesses is proved. Operation of this expansive experiment is simple, and the expression of this model is relatively concise, whose parameters are easily obtained. This model can be used in numerical calculation and simplified calculation, which has good practical value.

The subgrade frost boiling under ballastless track is a special form of high-speed railway subgrade defects appearing in recent years. In order to study the effect of the frost boiling on dynamic characteristics of ballastless track subgrade, in-situ survey and train-induced vibration tests were carried out in Shanghai-Nanjing intercity railway defects section. The vibration characteristics of ballastless track subgrade under the condition of forst boiling are analyzed. The results show that the subgrade frost boiling mainly resulted from the high content of fine particles in graded gravel and the cracking in expansion joints and side joints of foundation plate. The frost boiling at subgrade bed reduces the support and constraint effect of subgrade on the ballastless track, and intensifies the vibration of ballasted track structure, especially to the foundation plate of ballastless track. The vibration amplification effect increases with the increase of train speed. The defect also changes vibration wave transmission between ballastless track and subgrade bed, which restricts the energy dissipation function of subgrade bed. When the train speed reaches 247 km/h, the amplitude of vibration displacement at the surface of subgrade reduces by 45%. The vibration displacement transfer function from the foundation plate to subgrade bed decreases by 2/3, and the value is between 0.22-0.39 in dynamic loading mainly frequency range (0~15Hz) of the subgrade.

Tensile cracking-sliding loess collapse is the most recurrent disaster in the expressway construction in loess area. The maximum vertical tension cracking depth in trailing edge of loess slope is obtained from the limiting equilibrium equation of soil; the constitutive relation between vertical fissure mass and the potential sliding surface mass is established by the water weakening function; the equation of balanced camber and cusp is formulated from the expression of total potential energy of the collapse, then the catastrophic model of cusp for tensile cracking-sliding loess collapse is established. The formation mechanism for tensile cracking-sliding loess collapse is explored based on the mode. After excavation, the tension crack in trailing edge of loess slope is formed, and then the fissure is filled with water. The water filling increases the shear modulus of vertical tension and decreases the shear modulus on the potential sliding surfaces. When the saturation degree of loess mass reaches a certain value, the slope system undergoes mutation and the sliding surface is formed; then the core of the soil body moves unceasingly to the free surface. Once the core of soil body sliding out of steep slope, collapse will be happen. Based on the limiting equilibrium equation and the Mohr- Coulomb's law, computing formula of the stability for cracking-sliding loess collapse is established. The research results will be of valuable reference for the design and construction of loess collapse control.

To deeply know transfer properties and distribution model of negative pressure in fresh hydraulic reclamation muck foundation in the process of vacuum preloading technology with no-sand horizontal drainage cushion, based on a similar project in Gaolan Seaport Area in Zhuhai Seaport, a field experiment research was carried out. The research results show that: (1) Vacuum negative pressure reduced by at least 16% in the process of transferring to horizontal drainage cushion, and reduced by up to 57% in the process of transferring to the bottom of vertical drains. (2) For transfer properties of vacuum negative pressure in different depths, to a certain extent, it depends on dead weight sedimentation behavior of soils in different depths. The higher the content of coarse particles in certain depth is, the less the loss of vacuum negative pressure in corresponding depth is. But on the whole, the loss of vacuum negative pressure in the transfer path from vertical drains to soil is very serious, at least 67%, which is the main reason why soils strength is increased only a little after improved by no-sand vacuum preloading technology (NSVPT). At last, it is put forward that the distribution model of vacuum negative pressure. It is time-varying linear attenuation model when transferring in the horizontal drainage cushion; but it is time-varying nonlinear attenuation model when transferring in the vertical drains, depending on the site condition.

In the microscopic view, rock is composed of crystal grains and the contacts between them. During the chemical weathering process, the bonding materials are corroded and the connections between the particles are weakened which would lead to evident aging effect on the mechanical properties of rock. Based on the existing contact model, the chemical weathering process of rock was idealized as the solution of the bonding materials which resulted in the decay of the strength and stiffness of the bonds between the particles. In this way, the factor of chemical weathering is induced into the existing contact model. According to establishing contact model considering chemical weathering, DEM is used to simulate and analyze the corroded experiments and the discrete element simulation results. The results show that: the new model can reflect the aging effect on the strength of rock; the strength will decrease with the erosion; the new model can reflect the aging effect after the fracture pressure stage in the compression test. The elastic modulus and failure strain will decrease with the erosion; the failure of bonds between the particle, namely the growth of the microfracture, is the reason that leads to the aging effect. At the same time, the simulation results of the tests combined chemical weathering and loading show that a suitable construction speed should be chosen to ensure a safe and efficiency construction.

In view of the fact that the conventional formula or numerical method of penetration resistance for bucket foundation do not take the soil squeezing effect into account, large errors may occur for some bucket foundations with small diameter or large diameter with bulkheads in it as the restriction effect from the cylinder wall or bulkheads induced higher soil squeezing effect inside the cylinder than outside. In order to reveal the difference of soil squeezing effect between interior and exterior, an arbitrary Lagrangian– Eulerian method is used to simulate the dynamic continuous sinking process for real simulation of the soil squeezing effect during sinking by overcoming the problems which involve large deformation and nonlinear contact. The numerical analysis results show that the earth pressure of the internal cylinder wall is almost 10 times higher than that of the external wall when the ratio of the embedded depth to the diameter is about 1.6. The mechanism of the soil squeezing effect is elucidated by analyzing the soil squeezing displacement and stress distribution. At last, a penetration resistance formula for bucket foundation considering the effect of soil squeezing is proposed which obviously improves the stability of penetration resistance calculation since the calculation results are in good agreement with the test results.

In light of the limitation of the traditional response surface method for slope reliability analysis with high nonlinear implicit performance function, Gaussian process regression (GPR) model，which is a capable of solving the highly nonlinear regression problem with small samples and high dimensions, is applied to rebuild response surface of implicit performance function. Basing on the optimum sample selected by the function of uncertainty evaluation of GPR model, an iterative algorithm is presented to update GPR response surface self-adaptively. Thus, a new method combing GPR based dynamic response surface with Monte Carlo Simulation (MCS) method for slope reliability is proposed. The accuracy and feasibility of the presented method are demonstrated by numerical examples. The reliability of three slopes are analyzed using the presented method. The results show that the proposed method has higher efficiency and higher accuracy compared to traditional response surface method. It could be achieved easily and can directly take advantages of existing slope analysis codes without any modification. Thus, the proposed method provides a powerful tool for fast analysis of slope reliability.

A model consisting of three-dimensional (3D) layered saturated ground and absorbing boundary applied at the bottom was established in this paper. By introducing the Fourier and orthogonal transformations, Biot’s equations for the saturated soil are generated into equations governing Love and Rayleigh modes. By dividing the ground into several thin layer elements along the vertical direction and introducing linear interpolation function for the elemental displacement fields, the equations governing Love and Rayleigh modes for a single thin layer element are derived and then assembled to obtain global modal equations. After solving the homogenous global modal equations, the eigenvalues and corresponding eigenvectors of the saturated ground are obtained for Love and Rayleigh modes, separately. Eventually, the Green function for the 3D saturated ground is obtained for point loads by mode superposition method. Numerical results are presented to portray the evolution processes of eigenvalues of Love and Rayleigh modes with respect to the increasing excitation frequency and soil permeability. The Lamb problem of a homogeneous and layered saturated half-space is solved and compared with the numerical integration solutions given by Philippacopoulos. Through the comparisons, the obtained Green function is proven to be valid and accurate. Meanwhile, it does not require numerical integration with respect to Hankel functions and can take the soil stratification into consideration in a natural way, so as to improve the computation efficiency.

In this paper, an analysis algorithm which can be used to determine critical sliding surface and critical height of slope, based on numerical stress field, is presented. Upon the algorithm, firstly, the stress field of slope can be obtained by using the finite element analysis method to get more accuracy. Secondly, through simulation of slope, the laws of generation and movement of particles similar to the process of chain reaction are studied. Finally, the critical sliding surface can be determined. Therefore four conclusions can be drawn: (1) A method for determining the critical sliding surface of slope on account of numerical stress field is proposed, which can find potential failure path while no disturbance of the shape and location of slope sliding surface. (2) By controlling such four factors as range and boundary, excitation source, diffusion path and path metrics, the algorithm can get higher accuracy and simultaneously higher efficiency. (3) The algorithm takes the effect of strength anisotropy on stability of slope into consideration. And it is valid to compute the critical slope height. (4) A detailed calculation example has verified the proposed algorithm. Compared to calculation results obtained by the two methods of PSO and Monte Carlo, the reliability of the algorithm could also be proved.

As a basis of crack research of expansive soil, crack features of quantitative description contributes to further investigate the influence of cracks on engineering properties of expansive soils. Taking surface cracks of expansive soil as research objects, crack images are captured by using digital imaging, and parametes of crack features are obtained through optimizing and improving methods of crack image processing and crack feature extraction. For methods of crack image processing, it showed that improved local threshold binarization method could distinguish crack and background better than Ostu method. By marking connected areas, globally distributed noises on the crack binary image is eliminated effectively; and employing closing operation, tiny holes and gaps could be filled. The above methods make the crack binary image clearer and more reliable. For crack feature extraction methods, lookup table method is adopted to quickly identify crack endpoints and intersections, which helps count number of crack branches. Improved endpoints recognition algorithm was used to remove burrs from crack trunk, which makes the statistics of crack length more accurate. And improved minimum enclosing rectangle algorithm is used for statistics of crack width, which improves the calculation accuracy and saves the calculation time. Rose diagram is employed for statistics of crack orientation, which could be more intuitive to analyze the change law of crack orientation and number.

In order to show the mechanism of piping development considering development of weak zone, three models are built by means of flume model tests and PFC3D software to study the influence of the extended pore channels on particle migration process. The dynamic process of piping caused by the transportation of fine particles in the soil is studied by sand launder model test of piping and numerical simulation of PFC. Based on the results of the numerical simulation, the rules of the sample’s meso-movement and the liquid’s movement are studied and are compared with the results of sand launder model test. The simulation results agree well with the model test results. The result indicates that the larger the size of weak region, the greater the pressure change, the more loss of particles, the shorter the time to failure is. The result indicates that the critical hydraulic gradient derived by numerical simulation is nearly equal to that derived by sand launder model test and theoretical analysis. Therefore, researching the piping by PFC is reasonable, there are great practical significance and broad application prospects for the study of piping development considering development of weak zone. The results are valuable to further probing into the piping mechanism in sandy soils.

In the permafrost region and artificial frozen soil engineering, there are massive interface layers between frozen soil and architectural construction, but it is lack of experimental methods for frozen soil-structure interface mechanical deformation research. For this, based on the developed apparatus called large-scale multi-functional cycle direct shear system for frozen soil-structure interface ( DDJ-1), the shearing box of frozen soil was modified to highlight the interface layer of frozen soil ,and the measuring system of tiny deformation was developed, thus the experimental system was composed. Using this system, the mechanical properties experiments of interface layer can be performed under different boundary conditions; the displacement of soil can be measured in different positions; and the deformation properties of interface layer can be studied under different temperatures, roughnesses and normal stresses. The results show that, the apparatus can accurately reproduce the mechanical and deformational behaviors of the interface layer between frozen soil and structure; meanwhile, it can provide a experimental basis for carrying out researches on the frozen soil-structure interface layer.