In order to study the properties of anisotropically consolidated silt subjected undrained cyclic principal stress rotation, series of tests are performed. The tested hollow cylinder silt samples have the initial relative density of 70%, and are consolidated with different consolidation ratio(Kc) before cyclic principal stress rotation.The results show that for the samples with Kc≤1.5, they collapsed at low or medium strain and liquefied, but when Kc > 1.5, the samples’ strain increases stably and the pore water pressure developed into dynamic equilibrium states; and the peak values of pore pressure in dynamic equilibrium states are lower than those in the liquefaction failure states. On the other hand, differing from the isotropically consolidated samples, the samples with Kc between 1.1 and 1.5 have the maximum pore water pressure at liquefaction lower than the initial effective spherical stress. Furthermore they decrease with the increase of Kc, but barely dependent of dynamic shear stress. So do the pore water pressure at collapse states. The collapse cycles of anisotropically consolidated samples are larger than that of the isotropically consolidated ones with the same shear stress level. But there are no monotonic relationship between collapse cycles and Kc. Finally, a model of pore water pressure development for the anisotropically consolidated silt under cyclic principal stress rotation is put forward, which could reflect the collapse characteristics as well as the effects of consolidation ratio and dynamic shear stress level.

Size effect and wall effect are very common problems in seepage test of broadly graded coarse materials. A series of seepage tests are performed. The size effect is analyzed and the principle for apparatus size selection is studied. It is proposed that the apparatus diameter is not less than 6 times of test material’s d85. Effects of different methods for treating grains of size over limit on permeability test results are discussed. It is concluded that carefully taking equivalently alternative method is acceptable; while scale method is not. The wall effect is discussed and the thickness of wall treatment layer is proposed.

According to the constitutive equation of rock brittle fracture and 3D renormalization group theory, it is obtained the mathematical expression of stress ration between the critical point before fracture and peaking point. The acoustic emission (AE) characteristics of deep purple red sandstone under uniaxial compression are tested and obtained in the laboratory. According to the relevant test data, it is shown that the stress ratio between the AE mutation of critical state and peaking state has a value of nearly to 74%, and the deviation is less than ±9%.

To research the influence of water content (optimum water content, flow lower limit water content, flow upper limit water content) on basic properties of light weight soil, engineering properties of mixed soil are investigated by density test and unconfined compressive strength test. The results show liquidity of mixed soil can be controlled feasibly by liquidity indexes . When water content are on the points of flow lower limit water content and flow upper limit water content, unconfined stress-strain relation curves are almost coincident. So when water content is between flow lower limit water content and flow upper limit water content, engineering properties of mixed soil are approximative. Unconfined compressive strength decreases rapidly with increased water content, but there are no significant differences for the strength on the points of flow lower limit water content and flow upper limit water content. No matter how much the water content is, strength-age relation can be predicted by hyperbolic model. Empirical relations between strength of 7 d and 90 d and strength of 28 d are summarized. When water content is optimum water content, there is only a little shrinkage. When water content is between flow lower limit water content and flow upper limit water content, the range of line shrinkage ratio is [1.53%, 4.71%], and the range of volume shrinkage ratio is [4.53%, 13.46%]. Shrinkage property can be influenced by water content and cement dosage. Wet density of mixed soil can be predicted approximately by ideal density model, there is some error for predictive value, and error range is [3.834%, 8.231%].

Test data show that dynamic deformation characteristics of Shanghai soft soils are consistent with law of strain softening; and they can be described by Davidenkov model well. Firstly, based on Davidenkov skeleton curve, the dynamic shear stress-strain curves for loading and unloading are constituted by Masing rules; and the equations of incremental tangent shear modulus of skeleton curve and hysteresis curves are derived. Then the dynamic stress-strain relation is extended from one-dimensional to three-dimensional strain space. Using the development platform of FLAC3D, the nonlinear dynamic model of soils is programmed, which is based on Davidenkov skeleton curve and according with generalized Masing rules; and the validity and rationality of the program are validated by a complex stress-strain loading path. Finally, based on the soft soils test data of other related study, the calculated results by the program and test data results of related study, which contain the relation curves of dynamic shear modulus ratio vs. shear strain amplitude and damping ratio D vs. shear strain amplitude , are compared under series of different levels of shear strain amplitude. Study results show that compared with Hardin-Drnevich model which is widely used in engineering, the - curves and D- curves based on the Davidenkov skeleton curve are fitting to the soft soils test results better, so as to prove the rationality and practicability of the proposed constitutive model, and can be used for the dynamic response analysis of soft soils sites in Shanghai.

The presence of cracks can trigger landslide after rainfall. The saturated/unsaturated hydraulic conductivity is a key parameter to study the slope stability. In this research a random crack is made using high-resolution machine. An apparatus is developed to conduct seepage experiment through the random crack; and the saturated hydraulic conductivity of the crack can be obtained. The unsaturated hydraulic conductivity is predicted using the saturated hydraulic conductivity and the soil water characteristic curve. Results show that the saturated hydraulic conductivity is 0.1 m/s when the average aperture of the random crack is 0.4 mm. The hydraulic effective aperture is 0.35 mm, which is smaller than the average aperture. The hydraulic conductivity is proportional to the square of the average aperture, which is consistent with the cubic law. The unsaturated hydraulic conductivity curve shows that the hydraulic conductivity decreases very fast when the matric suction is larger than the air entry value. When the matric suction reaches the suction corresponding to the residual water content the influence of matric suction on the hydraulic conductivity is limited. Finally, the hydraulic conductivity approaches a constant value.

It’s important to study the relationship between water content and shear strength of unsaturated soils for engineering practice. On the basis of concluding the previous tests results, direct shear tests of undisturbed soil and remolded soils of which the water contents are controlled by two different ways are conducted, choosing the unconsolidated silt of Tertiary as a study object. The results show that the shear strengths of soils decrease with increasing the water content. The main influence of increasing water content on shear strength is decreasing the cohesion; and the influence on the internal friction angle of soils is little. The relationship between cohesion and water content of unsaturated soils can be described by two lines and the slope of the second line is greater than the first line which imply that when water content reaches some value, the cohesion of soils decline fast. The way to change the water content of remodeled soils by controlling the dry density of soils and adding different mass of water, has not only changed the water content of soils, but also the compaction and structure of soils. So the change of shear strength is influenced by both water content and compaction of soils; and it should be paid close attention when analyzing the test results.

Based on the concept of settlement controlling design, the composite piled foundation of raft, cushion and scattered piles has been applied to the ground treatment of Beijing-Shanghai high-speed railway ballast track, in order to achieve the goals of effectively reducing the post-construction settlement and make full use of the natural foundation bearing capacity. The field test of CFG(cement fly-ash gravel) composite piled foundation has been carried out to explore settlement controlling mechanism of the foundation reinforcement technology. Through long-term observation of foundation settlement, the pressure of pile and soil, raft pressure at the top and bottom during the process of high-speed railway filling, standing and preloading and unloading; the variation laws of the embankment settlement , pile-soil stress ratio and load sharing ratio, and the variation of raft pressure with the changes of both the filling height of the embankment and the consolidation time are analyzed. The results indicate that the soil between piles shares large loading pressure in the early filling, which resulted in differential settlement between piles and soil; and then raft can significantly improve the bearing capacity of piles and stress concentration degree of pile top under the regulating role of the cushion; and the settlement of foundation soil occurs mainly in the reinforcement area. Measured results provide experimental basis for revealing the bearing mechanism and deformation characteristics of composite pile foundation, and guide the optimization of design parameters of high-speed railway CFG composite piled foundation.

In order to study the influence of water content on the strength and deformation of slip soil, select a large scale landslide’s slip soil is selected to conduct consolidated-drained triaxial shear test with different initial saturations. Study the volume strain of unsaturated soils is studied by adopting a new gas and water converting device. The results show that the water content has great influences on the strength of slip soil; the higher the initial saturation is, the lower the strength value is. Strength parameter c with saturation is the ladder-like drop relationship; and linear relation could be established between strength parameters ? and initial saturation. The higher water content is, the smaller the soil sample’s volume deformation is; and the parameters of Duncan-Chang model such as K, Kb, and G are affected largely by water content; and then the linear formula could be established between the initial saturation and these parameters of Duncan-Chang model. But other parameters of Duncan-Chang model such as n, m, F, Rf, and D, which are little affected by water content, have little difference value under different initial saturations, so the averages are made as the model parameters under different saturations.

Laterite soil is one kind of high plastic clay being very sensitive to environmental heat and moisture variation, and mixing optimal ratio of lime into laterite soil is made when construction to improve pavement performance and prolong the life span. Engineering properties of subgrade are obviously affected by soil moisture state and its drying-wetting history during excavation and exertion of the expressway. Experimental investigations on strength and deformation properties of lime-treated laterite soil and laterite soil are carried out, considering two drying-wetting paths which are exactly accordant with practices. The results indicate that: with uniformity drying-wetting cycles, lime-treated soil, internal friction angle increase a little and cohesive strength decrease with shearing strength reducing and pavement performance has not improved greatly. With directional drying-wetting cycles, lime-treated soil have less drying-shrinking cracks with unconfined compression strength and deformation resistance decreasing a little and the long-term strength and deformation performance enhanced significantly.

In order to study the complex characteristics of double-arch tunnel during excavation, model and in-situ monitoring based on a double-arch tunnel with integrated middle wall are conducted to study the displacement and the stress of middle wall during excavation by bench cut method with middle drift. The effect of each excavation stages is analyzed in detail. The test results show that the displacement and stress are effected more significantly by the excavation of calotte than by the excavation of bench. The displacement-time curve is in a shape of S and the maximum displacement locates at the top of later excavated tunnel. Because the excavation of tunnel makes the stress in the other side of middle wall increase greatly and the stress in the excavation’s side increase slightly or decrease, the bending moment in middle wall is induced with the direction from the earlier constructed tunnel to the other by the excavation of earlier excavated tunnel and decreases with the excavation of later excavated tunnel.

Gravelly soil has been widely used as impervious material in high earth-rock dam in recent years. Taking the 189m high Pubugou rockfill dam for example, the seepage stability experiment in the core wall material of Pubugou dam is described. The experiment results indicate that the content of fine material is the main factor which determined the seepage stability. Ways to distinguish fine-grained soil from coarse-grained soil, to calculate the optimal fine material content ,and to judge the seepage stability by fine material content are also compared. The test result addresses the assessment is valid that the gravelly soil can be the impervious body of a dam that which requires the content of grain size less than 5mm is more than 35% and grain size less than 1mm is more than 15%, while it is not regarded as an precondition that the grain size less than 0.005mm have to be more than 10%.

As the construction project of port terminals developing seaward, engineering geological conditions get increasingly complex; it faces major challenges to build high-pile wharf on super thick soft clay foundation. Prestressed high-strength (PHC) pipe pile comes to the fore in designing to build the super-long foundation because of the deeply buried bearing stratum. This paper analyses the bearing mechanism and transfer rule of super-long PHC pile through test piles and numerical computation of pile (Its design pile length is 85m.) from a military wharfs. It comes up with the improved hyperbolic model on the base of transfer function method, and calculates vertical static load of test pile. The results are as follows. The calculated values of pile axial force and pile top displacement agree well with measured values, so as to prove that the curves proposed in this paper reflect the actual situation of the interaction between axial loading PHC pipe pile and soil; and it can provide guidance to design super-long PHC pipe pile in soft clay.

Comparative tests on the density, mechanical and seepage properties of rockfill materials are performed by preparing the same in-situ grading curve as different grading curves based on the scale methods. The test results show that according to the scale by means of the equivalent replacement method, owing to that the content of soil particles less than 5 mm does not change and the filling relation between coarse and fine particles is poor, the corresponding density and mechanical properties are the worst, and the coefficient of permeability is the largest. According to the similar grading method, one of the hybrid methods, the content of soil particles less than 5 mm gradually increases and the filling relation between coarse and fine particles is obviously improved; the relevant density and mechanical properties become larger and larger, however, the coefficient of permeability gradually decreases. At present, there are no specific and definite stipulations for the grading scale methods in Chinese codes and specifications. It is necessary to propose scientific laboratory scale methods for rockfill materials based on large quantity of laboratory and in-situ tests.

A series of experiments of chemical grouting into a fracture with flowing water are carried out by using fracture grouting equipment based on orthogonal test design. The correlation among water plugging effect, seepage pressure variation, and grouting technology is obtained by analyzing the test results. The results show that the seepage pressure curves of grouting into a fracture with flowing water can be divided into four types, including single peak type, platform type, multi-peak type and ladder type. The water plugging effect is good when the seepage pressure curves are platform type and multi-peak type. It is poor for water plugging when the seepage pressure is ladder-type. In order to improve the water plugging effect and save the grout, the grout amount should be increased while the seepage pressure is peak type; but it should be decreased while the seepage pressures are platform type and multi-peak type; and the volume ratio of grout should be regulated to short gel time while the seepage pressure is ladder-type. The results can improve the efficiency and technology of grouting based on seepage pressure monitoring.

Based on generalized potential theory, the modeling principle of establishing soil constitutive model and soil-structure interface constitutive model are similar; but the former is established in three-dimensional stress spaces according to triaxial shear test; the latter is established in two-dimensional stress space according to simple shear test. Under the simple shear test condition, the soil-structure interface problem can be regarded as a two-dimensional question in the space composed by normal stress and tangential stress, and the test result can be considered as two vectors, which composed by stress and strain respectively. According to the mechanical behavior of interface, the potential function and plastic state equation are determined; and general description of multi-potential surface interface constitutive model is deduced. Further, taking the two potential functions equal normal stress and tangential stress respectively, and a simplified multi-potential surface model of soil-structure interface is presented, which can be directly applied to the finite element numerical analysis. Finally, the proposed modeling method is verified by test examples. The model prediction results have been compared with experimental data; and results show that the modeling method is reasonable and practical. Research results indicate that the method presented is more convenient to establish the soil- structure interface constitutive model; and the elastoplastic stiffness matrix can be directly obtained without the determination of plastic potential functions and yield function.

The vertical load field test of nine large-diameter cast-in-situ bored piles is made in Tangshan LNG tank area, in which three piles are of tip post-grouting; three piles are of expanded branches and bells by 3-way extruding arms; three piles are of squeezed branch. Based on the static load and pile stress test results, the vertical load transfer laws of these three kinds of different construction techniques of cast-in-situ bored piles are analyzed. The results show that: the loading-settlement curves of three different construction technology piles have no obvious inflection point; the post-grouting pile load transfer process performs the characteristics of friction piles; pile lateral friction bears all load; the piles of expanded branches and bells by 3-way extruding arms and the squeezed branch piles load transfer performs the end bearing the characteristics of friction piles, pile tip resistance is 20% to 30% of the total load; the axial force and the pile-soil relative displacement variation of these three different construction technology test piles are similar; the tip resistance and lateral friction play asynchronous and influence each other; the pile lateral frictions have shown intensification. The entire tank area requirements of the single pile bearing capacity is not less than 8 100 kN, the bearing capacities of three construction technology piles can meet the requirements.

Residual stresses at the pile pit during pressure grouting are studied theoretically based on the solutions of expansion of spherical cavity and one-dimensional consolidation. By analyzing of the dissipation process of residual stresses, the analytical solutions of residual stresses dissipation with time and diffusion radius are obtained for assumed initial exponential pore pressure distribution. Also, a simplified solution discarding effect of grout spread radius is compared with the present method for different relative parameters. Parametric studies show that rheological index, consistency index, compression modulus and consolidation time are the key issues affecting pile residual stresses. In addition, the validity of the proposed model is tested by comparing the results from field measurements. This research is great important for the theoretical studies and practical applications of the residual stresses.

After excavation of caverns, the surrounding rock mass of them usually generates a lot of stochastic distribution of penetrative cracks which directly affects the stability of surrounding rock mass. It is important to study the deformation and deformation characteristics of rock mass with stochastic distribution of penetrative cracks. Based on linear elastic theory and linear stiffness theory, the computational model of deformation of rock mass with stochastic distribution of penetrative cracks is established by probabilistic approach. Equivalent elastic modulus and equivalent Poisson’s ratio are also presented. The effects of material parameters and geometry parameters of rock and cracks on the equivalent elastic modulus and equivalent Poisson’s ratio of fractured rock mass are studied. The following conclusions can be concluded: the equivalent elastic modulus and equivalent Poisson’s ratio all increase with the increase of elastic modulus of rock. The equivalent Poisson’s ratio increases with the increase of Poisson’s ratio of rock. The equivalent elastic modulus and equivalent Poisson’s ratio all increase with the increase of normal stiffness of cracks. With the increase of shear stiffness of cracks, the equivalent elastic modulus increases, while equivalent Poisson’s ratio decreases. With the increase of mean space of cracks, the equivalent elastic modulus decreases, while the equivalent Poisson’s ratio increases when the mean dip is smaller and decrease when mean dip is larger. With the increase of mean dip of cracks, the equivalent elastic modulus firstly decreases and then increases, while the equivalent Poisson’s ratio firstly increases and then decreases. The model can more comprehensively consider the effects of material parameters and geometry parameters of rock and cracks on the deformation of rock mass. So the model has some reference value in studying deformation of surrounding rock mass of caverns.

The problem of site selection evaluation for salt cavern gas storage arises along with the rapid development of salt cavern gas storages. Based on the classification of the influence factors and the analysis of site selection for salt cavern gas storage, Analytic hierarchy process is used to build a layer structural model. Using expert investigation method, the importance weights of 18 influence factors are obtained. Then taking the advices of the experts on salt cavern gas storage building and the related research results into consideration, index suitability standards and synthetical evaluation standards of site selection evaluation for salt cavern gas storage are put forward. Combined with the importance weights of 18 influence factors, a formula is developed to calculate the synthetical appropriate value P of site selection. The results provide a feasible method and theory for the construction of salt cavern gas storage in China. Finally, this method is used to evaluate the suitability of building salt cavern in Yunying salt mine. The result is consistent with the expert opinions, which shows that this method is reasonable.

Based on the principle of enlarging perimeter with the same section area, X-section cast-in-place concrete pile (abridged XCC pile) is developed by changing the convex of circular-section to concave. As a new special section pile, the ultimate bearing capacity is calculated by empirical formulas in standard. The in-situ static load tests are carried out based on the foundation treatment project in Qiaobei sewage treatment plant in Nanjing. Besides, a finite element model is established to simulate the XCC pile composite foundation under the rigid base by software ABAQUS. The ultimate bearing capacities are discussed considering some factors including elastic modulus of pile, modulus of surrounding soil, pile length, cushion thickness and cushion modulus. The results indicate that XCC single-pile composite foundation can increase the bearing capacity by 20% more than that of traditional pile. The ultimate bearing capacity of XCC four-pile composite foundation can increase the bearing capacity by 12.35% more than that of traditional pile. The ultimate bearing capacity increases with the increase of pile modulus, cushion modulus surrounding soil modulus and pile length. From the factors, the effect of modulus of surrounding soil is most obviously.

This paper uses both linear and nonlinear strength parameters in several typical rockfill dams’ slope stability analysis, clarifies the intrinsic factors that lead to the differences; the position of critical sliding surface is considered to be shallow, thus, shearing strength of coarse grained materials at low confining pressure is vital in slope stability analysis. Based on statistics of rockfills in several typical rockfill dams at home and abroad, power function strength criterion proposed by De Mello is thought to be more reasonable to express coarse grained soils’ strength in its whole confining pressure range. By drafting dam slopes with different heights and gradients, working stress ranges are determined. This study suggested a method to specify the linear strength parameters based on working stress ranges, these linear strength parameters have a good consistent with nonlinear parameters in slope stability analysis.

As a typical oblique inclined bedding carbon slope, Jiweishan slope does not collapse laterally and results in a deposit landslide, but creeps down the dip at initial stage and then turns into an overwhelming apparent-dip rockslide. On the basis of field investigation, several causes of Jiweishan landslide are discussed in terms of lithology, structure, karstification and underground water, weak intercalation. According to failure mechanism, three dimensional stability of limited equilibrium analysis has been done based on key block theory. 3DEC software is brought in to study the apparent dip-sliding mechanism and deformation character by simulating the initial failure process. Parameters value of discontinuous and corroded rock mass for numerical analysis are also discussed. Conclusions could be drawn via analysis that the slope creeps down the dip initially under gravity and tension crack and lateral crack are generated along karstification steep-crossing joints forming independent driving blocks in the rear. Underground water continuously softens weak intercalation and that leads to rising of residual sliding force of driving blocks and stress accumulation in the key block. Finally, the intensive karstification zone is sheared, and it causes overwhelming apparent-dip rockslide. Numerical simulation results demonstrate that after shear strength reduction of weak layer the karstifiction zone is sheared and sliding masses enter into large-scale deformation stage. This shows controlling and hindering effect of the key block and the key factor of Jiweishan landslide’s occurrence is weak intercalation softening. It also indicates that mining goaf mostly leads to increment of compression stress in rock mass over the roof and does not affect displacement of sliding mass.

The chamber pressure control is a key operation for controlling the impact of the earth pressure balance (EPB) shield excavation on the environment. Based on the monitored data, the water and earth pressure distribution properties in chamber and at the excavation face of a super-huge diameter EPB shield tunneling are studied. According to the construction parameters analysis, it is found that the increment of chamber pressure could be calculated by the construction parameters, such as rotation speed of screw conveyor and advancement rate. In addition, the water and earth pressure at excavation face could not be transfer to the chamber completely, and the transmissibility is about 76.3%. The research results of this paper provide valuable references for the setting method of the chamber pressure of the super-huge diameter EPB shield.

For many unstable slopes, local or transient large displacement often occurs, even collapse due to excavation, rainfall or earthquake. The large lateral soil displacement may generate additional internal forces and deflection in stabilizing piles. Based on the two-stage method, the Winkler’s model is adopted to simulate the effect of pile-soil interaction, and the horizontal displacement control equations of a single pile are established. By considering the continuity condition and the boundary conditions, the analytical solutions of control equations are obtained and verified by monitoring data and Poulos’s elastic continuum method. Finally, with the typical engineering accident, the influence of lateral soil movements on adjacent stabilizing piles in slope is investigated by parametric analysis. It shows that the pile deflection and bending moment are obviously affected by soil lateral movement model, such as maximum displacements, distribution shapes and center of gravity, displacements energy, etc, on which it should be pay more attention practically.

Soil-water characteristic relationship is a function about the connection between matric suction and water content. The research shows that the air-entry value has great influence on the drying scanning curve when the starting point of the curve is near the highly saturated level. A capillary hysteresis internal variable model (HIVM) put forward by Wei Changfu is able to simulate the hysteresis characteristic of the scanning curve; but the influence of the air-entry value is neglected. There exist some deviations between the simulation of the drying scanning curve and the factual results. Based on the theory of HIVM and the empirical model about the traditional soil-water characteristic relationship, a modified HIVM is put forward. The influence of the air-entry value on the drying scanning curve whose starting point is near the highly saturated level is considered in this new model. While in drying path, the effects of air-entry value on the scanning curves that the original points at the highly saturated range is considered. According to the data from the simulation calculation to the various soil samples, in the modified HIVM, the influence of the air-entry value on the drying scanning curve is considered; so it is better than the original model.

Practical engineering activities are closely related to engineering properties of soil-rock materials under low confining stress. Cases of landslides of Levees and dams due to earthquake were summarized and analyzed; and it revealed that the depth of landslides was usually less than 7m, and the effective overburden stress was usually not more than 100 kPa. 106 cases of the foundation liquefaction were analyzed; and it is revealed that the foundation liquefaction occurred mostly at where the effective overburden stress below 100 kPa. In the present study, only the properties of soil-rock materials under high confining stress are paid great attention, and in applications the parameters of soil-rock materials under low confining stress are assigned the same as those under medium to high confining stress; while the reliability of this parameter selection method is disputable for the properties of soil-rock materials are seriously dependent on the stress. Therefore, study of the engineering properties of soil-rock materials under low confining stress and discussing the corresponding parameters selection method in numerical simulation have great significance both to engineering practice and scientific research.

Pit-in-pit excavation is becoming more and more popular, and concerns are increasing on the influence exerted by the interior pit. However, the calculating depth in design remains a puzzle, taking the exterior pit excavation depth is a risk, while the interior is conservative. This paper raises a concept of equivalent depth and two parameters called equivalent depth coefficient and equivalent impact angle based on analysis of various relative position of interior and exterior pit, width and depth of the former, whose feasibility is proved. The equivalent depth converts the pit-in-pit into normal excavation model, and the equivalent depth factor quantifies this kind of conversion.

The Kala Hydropower Project, located in a narrow and deeply-cut valley on the middle course of the Yalong River, is subjected to serious seepage and leakage problems due to complex geological conditions at the dam site. In order to reduce the quantity of seepage flow through and around the gravity dam and prevent the dam and its foundation from seepage failure, a seepage control system consisting of grouting curtain, drainage hole array and drainage tunnels is designed. For performance assessment and optimization design of the seepage control system, a numerical method combining a substructure technique, a variational inequality formulation of Signorini’s type and an adaptive penalized Heaviside function (short for SVA method) is adopted. Numerical results at a typical overflow dam section and the whole dam site demonstrate that the primary design is a proper and considerable scheme for seepage control but further optimization can be performed in designing the layout. The results show that: ① the grouting curtain can effectively raise the groundwater level at the upstream of the grouting curtain, increase the bypass seepage path and reduce the uplift pressure in the dam foundation, and the drainage system can significantly reduce the pore water pressure in the dam body and the uplift pressure in the dam foundation; ② the drainage hole spacing has significant effects on the free surface locations with an appropriate spacing of 3.0~4.5 m.

The containing water body is one of the primary factors to impact the safety in production all the time. The transient electromagnetic method plays an important role on the advanced detection of water disaster in tunnel. Because of the detecting particularity in full space condition of tunnel, the detecting and forecasting results are often affected by the layout way of detection, and it often expresses in serial fields such as the interference factor rejection, depth calculation of resistivity, space judgment for abnormality, and so on. For acquiring more reliable detecting results, the testing arrangement is improved in the article. The detecting section in the direction of centre line is added, and it forms the detection method of four-section ahead of tunnel with the roof section, along tunnel section, and bottom floor section. The judging ability of space for the containing water body ahead of tunnel is enhanced. Through contrasting the results of the convention detecting pattern, the advantage of four-section method for geology body judgment is analyzed because of its combining cross-section and longitudinal section. The detecting practices show that it is reliable to use under 10 ?•m as the criteria of the resistivity to forecast the low resistivity field in the tunnel along the 6 coal seams for the advanced detection by the four-section transient electromagnetic method. It has important instructing value for driving safety of tunnel.

X-section cast-in-place concrete pile (XCC pile) can save concrete usage under the same pile perimeter. However, there were relative little studies of the lateral bearing capacity affected by X sectional shape. Based on three key control sectional parameters (outsourcing diameter, open space, and open arc angle), the moment of inertia equation under arbitrary direction axis are built. Then, the moment of inertia influenced by sectional parameters are discussed. Finally, optimized X section type is proposed, of which the moment of inertia can be improved with the same areas or perimeter. The results show that, the moment of inertia increased with outsourcing diameter increasing, open arc degree decreasing, and open space decreasing. Hence, appropriate increase outsourcing diameter, and reduce opening angle and arc, can help improving the moment of inertia, thereby improving the overall bearing capacity of X-section cast-in-place concrete pile.

A predictive model of ultimate bearing capacity for large-diameter and super-long steel pipe piles is established based on Support Vector Machine(SVM) and Independent Component Analysis(ICA). Firstly the FastICA algorithm of independent component analysis is imported to abstract the independent components, which can better express the essence in sample data and keep statistics independent without correlation as well as obey the Gaussian distribution, from large-diameter and super-long steel pipe pile data measured in an actual engineering. Secondly, by determining the support vector machine as classifier, whose input are the previously extracted components and whose output is the predicted bearing capacity, ICASVM_Q model is established to predict bearing capacity of large-diameter and super-long steel pipe piles. By data testing of a bridge engineering, it is shown that the predicted results of ICASVM_Q are better than SVM_Q which uses original engineering data as input of SVM model. Studies indicated that the modeling method by combining SVM and ICA used to predict ultimate bearing capacity of large-diameter and super-long steel pipe piles is feasible and the predicting bearing capacity of the ICASVM_Q model can be referred by designers in engineering. This method can also serve as a reference of intelligent forecast in other areas.

Suction embedded plate anchors are used to moor large floating structures in deep water. The loss of embedment due to keying of plate anchor during installation needs to be predicted accurately in practical applications. The keying process of frictional anchors in normally consolidated clays is investigated using a large deformation finite element approach. In the large deformation analysis severe distortion of the soil mesh, which is induced by significant translations and rotation of the plate anchor, is avoided by frequent mesh regeneration. The maximum shear strength along the ‘anchor-soil’ interface is updated by means of current embedment depth of the anchor. The numerical results are validated by comparisons with the experimental data from centrifuge model tests. It is found that the roughness factor of ‘plate anchors-kaolin clay’ interface is valued about 0.3. Totally, the loss of embedment is increased with reduction of roughness factor; however, the loss of embedment depends on the combined influences of anchor roughness, anchor thickness ratio and eccentricity ratio of the pulling force. The influence of anchor roughness on the embedment loss may be enhanced when the thickness ratio and the eccentricity ratio become smaller.

For the foundation, slope and backfill supported by retaining wall, which consist of the over-consolidation clay, dense sand or non-associated plasticity material, the appearance of strain localization during the gradual process of the failure and instability of these geotechnical structures will lead to the change of the type of governing partial differential equation. Furthermore, this change results in non-unique and the mesh-dependence of solutions obtained by standard finite element method (FEM). In order to overcome these difficulties, on the basis of the strong discontinuity analysis (SDA), the embedded discontinuity finite element model is employed to investigate the failure processes of foundation, slope and backfill. Numerical examples show that this model can effectively simulate the post-failure processes of geotechnical structures and improve the objectivity of response with respect to the mesh size. The results also show that, this method can be taken as a beneficial supplement to traditional limit equilibrium method in stability analysis of slope and foundation.

Field measurements from practical projects show that the deformation of enclosure structures of narrow foundation pits is relatively smaller than that of super-wide foundation pits; and the latter is often accompanied with kick-out deformation. As the conventional finite element method commonly doesn’t consider the influence of the excavation width on earth pressure on enclosure structures, which causes the design for narrow foundation pit more conservative and results in wasting more, and it also takes more risky for design of a wide pit and creating risks during construction. This paper derives a new calculation method adopting reduction factor of load on the enclosure structure, taking impact of excavation width into consideration. From which the load value is regulated to improve the bar-system-FEM commonly used for foundation pit design. Three centrifuge model tests have been done for foundation pits with different widths of 24 m, 32 m and 42 m respectively. The test results show that the calculation results of the traditional bar-system-FEM are obviously incompatible with the test results when the impact of foundation width is considered. The theory of this paper is used to analyze the test results, which proves the reasonableness of the method. This method is a necessary amendment to the bar system FEM and deserves the popularization in the design of foundation pits.

A model considering rolling resistance in particles is introduced into the distinct element method (DEM) for analyzing the earth pressure against a rigid wall subjected to translation movements in the passive state. The evolution of earth pressure with the wall displacement is analyzed together with micro mechanical parameters by comparing the cases with and without considering the rolling resistance of particles in the granular backfill. Results show that the earth pressure increases linearly with the increase of the wall depth regardless of the effect of rolling resistance; and the total thrust acts at approximately one third of the wall height from the base of the wall in both cases. The increase of the resultant earth pressure with displacement is more prominent in the case considering rolling resistance than that neglecting the rolling resistance. The result considering rolling resistance is more close to the classic Coulomb's solution. According to the field of average pure rotation rate, the velocity of soil particles adjacent to the base of the rigid wall is larger, implying a quick energy dissipation taking place at that region, and it becomes even larger in the case considering the rolling resistance than that in the case without considering the rolling resistance.

The problem of pile foundation response to impact loading on adjacent field is a dynamic interaction of the whole system consisting of piles and soil under the impact load. To study the potential vibration of the pile foundation affected by impact loading on adjacent field, the vibration is simulated with finite element method (FEM). Using FEM software of ABAQUS a coupled finite element-infinite element (FE-IFE) model is created; the pile foundation response to impact loading on adjacent field is analyzed; then the factors affected pile foundation response are considered; some useful conclusions are drawn; the value of vibration amplitude is determined by energy of impact loading and distance between pile foundation and impact site; and the wavelength of pile foundation vibration is determined by distance between pile foundation and impact site.

Based on the theory of breakage mechanics，the structural loess is conceptualized as binary－medium model consisting of bonding brick and frictional band. Shear band is structural loess’ breakage, localization band sprout and development is dynamic process that bonding brick is translating into frictional band. Applying the double parameter breakage ratio binary-medium model of structural loess, the process of structural loess localization band sprouting and expanding is simulated with the numerical simulations method, the localization shear band shape, speciality and law under different disfigurement project are studied; it is found that the strain localization on a shear band of structural soil at originally is some sets discontinuous little local breakage area step by step developed, connected and formed the shape of whole destruction with the external load increased. Combining binary-medium model with general finite elements, visual reappeared the course of the local shear band germination and progress.

The variation of temperature and pressure may lead to decomposition of gas hydrate in a hydrate-bearing sediment (HBS); meanwhile, several coupling processes are induced, including phase transition, pore water and gas pressures dissipation, heat transfer and skeletal deformation. A mathematical model is developed to describe the decomposition process of gas hydrate-bearing sediments based on the theory of porous media. The model properly considers the coupling effect among pore water/gas flow, phase transition, the kinetic process of hydrate dissociation, heat transfer and the skeletal deformation. Based on the finite element method, a numerical model describing the process of gas hydrate decomposition is developed and a computer program is compiled. Through numerical simulation of both depressurization-based and heating-based production processes, variation of displacement, pore pressures, temperature and other parameters in gas hydrate bearing sediments reservoir are analyzed. The results indicate that reservoir deformation and excess pore pressure are induced by depressurization and heating method with varying degrees, meanwhile, the seepage and heat conduction are contained in the gas hydrate dissociation process.

This paper presents a numerical study of the resistance and failure of cemented seabed burying an uplifting pipe using distinct element method (DEM). The mechanical properties of cemented sand are firstly simulated and analyzed with various inter-grain bond strength; and then, local deformation, distribution of broken bond, and displacement fields are investigated to analyze the failure mechanism of cemented seabed with different bond strength during pipe uplifting; Finally, uplift resistances and upheaval displacement of cemented seabed are discussed with respect to bond strength effect. The results show that the ground deformation and inter-grain bond failure are mainly located in overlying soils of the pipe. Furthermore, The backfilling of soils beneath the pipe vanishes as the increase of bond strength, an apparent tensile-failure rupture above the pipe, and an enhanced uplift resistance of cemented seabed are observed. In addition, the upheaval displacement of seabed increases with the pipe uplift displacement.

Draining is one of most effective seepage control measures for geomaterials and engineering structures, of which the essence is through forming the potential spillover boundary or low water level boundary in flow region to realize the seepage control. Induced by the seepage boundary of drains, the seepage flow may exhibit a strong nonlinear effect. The variational inequality formulation of Signorini condition has been theoretically proved to be an effective approach for steady and non-steady seepage problems with drains, but needs further experimental validations. For this purpose, a laboratory test is performed on the seepage behavior in a sand flume with five horizontal drainage galleries, then the effectiveness and correctness of the variational inequality method of Signorini condition is validated by experimental data. The experimental results show that: in steady seepage flow condition, the upstream three drainage galleries in the sand flume have a dominant effect on controlling the seepage flow, while the other two drainage galleries in the downstream side lose the draining effect; and the numerical results agree well with experimental observations. In non-steady seepage flow condition, the numerical results somewhat deviate from the experimental results due to low accuracy of piezometer tubes, inhomogeneity of the sand sample and negligence of capillary effect. The non-steady seepage flow process in the sand flume with complex drains, however, is still satisfactorily demonstrated. The effectiveness and correctness of the variational inequality method of Signorini condition is validated by the seepage flow test; and it provides an effective approach for optimization design of seepage control structure in geotechnical engineering under complex drains.

Due to the situation that intensive cavern group system has to be used to improve resources (oil & gas) storage efficiency in China, the stability and contraction distortion of the existing salt rock storage group model are discussed. The single cavity model and cavern group model are built according to the result of sonar cavity survey, and the influence laws that how cavern group operating model effects the cavern stability are proposed through the comparison and analysis of the simulation results. The laws show that asymmetric volume shrinkage and irregular deformation can be induced by the following three factors, the difference in position and depth, formation dip of interbedded and shape difference between adjacent cavern; different from which the maximum displacement zone usually appeared in a fixed position near the waist in single cavern model; there are no fixed position of maximum displacement because of the influence of nearby caverns in the cavern group model; with the properties of high stiffness, low creep resistance and the strong shear strength near the salt-mudstone interface, the mudstone can improve storage cavern integrity and stability when it penetrates the whole cavern group; considering that the stratigraphic dip interlayer deformation property has bad influence on the cavern group leakproofness, the stretching at the mudstone-salt interface and the torsional bending of mudstone can cause cracking in the mudstone layer: and the breakthrough crack could make single cavern lose the ability to operate alone and then affect the whole operating efficiency of the cavern group.

Infiltration of atomized rain by flood releasing is an important factor to the stability of slope by plunge pool for high dam. In order to analyze the effect of atomized rain infiltration in Wudongde hydropower station, the two-dimensional unsaturated and unsteady seepage field is modeled for a typical profile of plunge pool slope, and is simulated with the FEM. The range of the saturated zone and the pressure head of the groundwater in the slope during the infiltration is analyzed under different slope protection conditions. It is shown that for the slope formation with high permeable layer overlying relatively low permeable layer, the pressure head in the resistivity water layer will raise gradually with the increase of infiltration recharge. Application of impermeable material to the slope surface as protection treament can largely decrease the infiltration of atomized rain into the slope, thus the influence of atomized rain on the seepage field of slope is significantly reduced.

Discrete element method (DEM) is adopted to simulate the whole failure process of reservoir bank slope. The flow chart of this paper is carried out and its corresponding software is developed. The basic principles of DEM are introduced. The disadvantages of the existing methods of calculating landslide velocity and advantages of DEM are analyzed. The height and shape of the surge of the reservoir stirred up by the landslide is simulated by combining the block information provided by DEM and wave equation, the heap shape of the landslide is also carried out by DEM. The feasibility and accuracy of the method is verified by case studies. The results of the examples indicate that the block velocity on the slope calculated by DEM agrees well with that the energy conservation method and Pan Jiazheng method; the DEM is more convenience and has a higher efficiency. The height of surge stirred up by multi-blocks is greater than that of single-block due to the plus of surges, which indicates that it is important to consider the plus of surges when analyzing the height of surge. The heap shape of the blocks provides basic data for the disaster assessment of landslide. The sliding of the block and the generating and transmitting of surge are also carried out by a self-developed DEM software, which provides a new idea for the study of the start, the process and the risk assessment of slope failure.

Finite element method is often used for solving unsaturated soil seepage problem. However, numerical difficulties such as slow convergence rate and inaccurate results are commonly existed in numerical analysis because of the highly nonlinear soil-water characteristic curve and hydraulic conductivity function. Based on a rational function transformation (RFT) method, a new temporal adaptive transformation method with under-relaxation (ATUR1) is proposed to solve the unsaturated soil seepage problem. It is shown that the transformation in ATUR1 can reduce the nonlinearity of solution profiles of the Richards' equation both spatially and temporally; thus the inefficiencies in the numerical solution process caused by these nonlinearities can be overcome. The under-relaxation technique can further increase the efficiency by curbing the oscillation tendency during iterations; and the temporal errors during the whole simulation can be controlled effectively by the automatic temporal adaptive scheme. Numerical examples show that the proposed ATUR1 method is a robust and efficient numerical method for practical unsaturated soil seepage simulation.

With the rapid development of highway and runway construction and the widely application of silty sand subgrade, the stability of silty sand subgrade under aircraft loads should be further studied. Based on Byrne model describing the variation of pore pressure in saturated silty sand, the Lagrange difference method was introduced to analyze the effect of aircraft loading on silty sand subgrade pore pressure, displacement and instantaneous destroyed areas. The laboratory model tests were carried out to validate its rationality. Results show that the excess pore water pressure, displacement distribution and stress state in silt sand subgrade are influenced significantly by loading frequency, loading time and load peak,especially, loading frequency 5 Hz is a key control indictor and should be given consideration in the design.

In order to study the dynamic response of subway station structure subjected to surface ground explosion, a simplified model of airblast forces is demonstrated in detail. Whereafter, the improved concrete dynamic Cam-Clay model of soil and the concrete damaged plasticity constitutive model are used for the dynamic analysis of subway station when 100 kg TNT detonates on ground surface. Meanwhile, the influences of soil stiffness and buried depth on dynamic response of subway station are taken into consideration. Finally, the dynamic response of station structural subjected to far-field explosion wave is analyzed. The results show that, the central roof of station has small tension damage. When the buried depth is less than 5 m, the dynamic stress is larger. The smaller the covering soil stiffness is, the more energy of the explosion the covering soil absorb. As the frequency of the explosion waves is very larger, the dynamic stress of the station subjected to far-field explosion wave is smaller. The results will be benefit anti-explosion design of underground structures.