In this study, the effect of the loading angle on the flattened Brazilian test is reviewed and the correction coefficient of the indirect tensile strength formula is summarized. Three dimensional finite element models for the flattened Brazilian disks are established to study the equivalent stress distribution by considering two kinds of loading angles. Based on the Griffith strength criterion, the equivalent stress distribution is affected by the loading angle in terms of stress distribution along loading diameter and flat ends. Moreover, the maximum equivalent stress occurs at edges of the flat ends in both two models. Three dimensional discrete element model is also constructed to study the initiation and propagation of cracks in the flattened Brazilian test. The micro-cracks first concentre at edges of the flat ends. However, macro-cracks, which will lead to the final failure of the specimen, initiate at the central disc. The results from the finite element method and discrete element method can be verified mutually. Compared with experiment phenomena, it is found that the precision of the two flat ends have a significant impact on the fracturing mode. The method of placing shims between the specimen and test machine is feasible to conduct the flattened Brazilian test conveniently.

Defects exist in vertical reinforcement, such as drainage capacity and large bearing capacity cannot be achieved at the same time. This study developed a new type of porous pipe pile with drainage function. It is assumed the tube flow for pore fluid, and the continuous pore pressure according to Poiseuille equation. Then, the analytical solution of strain consolidation is deduced. The drainage pile presents the best consolidation capacity compared to sand drain, gravel pile and undrained pile. The effect of pile modulus, mattress modulus and radius ratio on consolidation are also analyzed. Drainage capacity and modulus are two main factors that affect the consolidation performance. The drainage capacity is the most important. Within the same drainage capacity, greater the modulus of the pile produces faster consolidation process.

Based on triaxial shear tests of structural cube loess samples with different water contents, residual strength effect and relationships between structural indexes and strength parameters are studied, based on which the uniform strength formula for plane strain is corrected. Variations of Mohr circle of soil stress behind the wall under the seismic conditions are analysed. By using the method of level layer element, calculating seismic passive earth pressure of loess filler considering intermediate principal stress, structure and residual strength effects is established. The results indicate that cohesions and friction angles calculated by unified strength theory increase with unified strength parameter b. The structure of loess has a huge influence on cohesion while the effect of friction angles is not obvious. The total seismic passive earth pressure coefficient increases with the increase of b value and structural index, while it decreases with the increase of horizontal seismic coefficient. The residual strength makes a more contribution to seismic passive earth pressure coefficient for large structure than for small structure.

In a strong earthquake, the liquefaction-induced lateral deformation of ground has induced severe damages to the ground structures and the underground lifeline engineering. It is foreseeable that the safety of subway underground structure is seriously threatened by the seismic liquefaction-induced lateral deformation of ground. For this reason, the earthquake response of a subway underground structure buried in a soil foundation with a slight inclined ground surface was investigated by shaking table tests. The results demonstrated that the soils beside the underground structure were not liquefied synchronously with the soils near the slope toe were easier to be liquefied than the soils near the slope top. When the soils in the slope was liquefied, they would flow down along the slope, which can induce the uplift of the ground surface near the slope toe. Meanwhile, it was found that the lateral deformation of soil in the slope was larger than that of soil near the slope toe, and the lateral deformation of soil near the slope top was smallest. The results also revealed that the underground subway station floated more severely than that of connected tunnel, which could induce seismic damage at the connection part between the tunnel and subway station.

Pre-disintegrating carbonaceous mudstone has been widely used in the embankment engineering as embankment filler in Southwest China. In order to study the deformation and strength characteristics of pre-disintegrating carbonaceous mudstone under loading and soaking condition, a new type of wetting deformation test device is developed. A series of deformation tests on pre-disintegrating carbon mudstone samples are carried out according to the orthogonal experimental design. The test results show that the pre-disintegrating carbon mudstone will exhibit a large vertical deformation at initial loading and first immersion, which consists of both compressive induced deformation and wetting induced deformation. The influences of vertical load, cycle number, immersion time, compactness and moisture content on the maximum vertical deformation of pre-disintegrating carbon mudstone decrease in sequence. The variation of shear strength during wetting deformation is mainly due to the change of cohesion. The influence level of cycle number, immersion time, vertical load, compactness and moisture content on cohesive strength of pre-disintegrating carbon mudstone decreases accordingly. The shear strength decreases sharply first and then tends to be stable with the increase of the vertical deformation. The function relation between shear strength and vertical deformation is obtained. The results can provide some references for deformation calculation and engineering practice of carbonaceous mudstone.

The segmental collapse of loess will not occur because of unloading. But loess collapse potential is generally evaluated without considering the influence of unloading. The coefficient of unloading collapse is obtained by unloading collapse test. The completion ratio of collapse is defined to represent the degree of loess collapse before unloading. The unloading ratio is defined to represent the degree of unloading. The calculation formula of unloading collapse coefficient is derived by completion ratio of collapse and unloading ratio. Through unloading collapse test, the unloading collapse of loess is measured in different unloading and collapse conditions. The specific expression of the unloading collapse coefficient is obtained by analyzing test results. It is suitable to calculate unloading collapse coefficient in either initial pressure, unloading amount and collapse condition. The calculated results based on the proposed equation are in good agreement with the test results. The loess collapse deformation have been further summarized by defining coefficient of collapse potential under the condition of unloading.

Microbial induced calcite precipitation (MICP) technology is applied to the formation of in-situ bio-mineralization crust on the surface of desert, which enables floating dune to be semi-fixed and fixed, hinders wind erosion, and fundamentally blocks the source of sandstorm. Two bio-mineralization test plots (TP1 and TP3) were built using two different microbial strains on the Aeolian sand surface in Ulan Buh desert, Inner Mongolia Autonomous Region of China. The field-scale experiment methods and processes were designed to evaluate and analyze the strength of bio-mineralization crust and its long-term stability in the desert environment. Staphylococcus, extracted from local Aeolian sand, and Sporoscarcina pasteurii, a traditional bio-mineralized bacterium, were used to induce the formation of calcium carbonate crystals. Through penetration tests in site, the penetration resistance developed along the depth of bio-mineralization crust was recorded on the 7th, 14th, 28th, 60th and 210th day. The strength of bio-mineralization crust was converted according to the value of average penetration resistance at 2.0 cm of the crust. The variation of strength of bio-mineralization crust with mineralization time was summarized. From visual observation in site, the bio-mineralization crust began to form on the 4th day. The average thickness ranges from 2.0 cm to 2.5 cm on the 7th day, and the strength of bio-mineralization crust induced from Staphylococcus was 1.05 times than that of Sporoscarcina pasteurii. For the bio-mineralization crust TP3 induced from Sporoscarcina pasteurii after freeze-thaw cycles on the 210th day, the average thickness decreased from 0.7cm to 1.0cm, the strength was reduced by 19% and the content of calcium carbonate was reduced by 15%-30% compared with that on the 7th day. However, the strength of bio-mineralization crust TP1 induced from Staphylococcus on the 210th day was reduced only by 2%, which is a little less than that on the 7th day. MICP technology can be applied to the formation of in situ bio-mineralization crust in desert. The bio-mineralization crust developed from Staphylococcus has better strength performance and long-term stability in desert environment than that from Sporoscarcina pasteurii.

A series of undrained triaxial shear tests on undisturbed Nanyang expansive clay under saturated K0 condition have been performed. Two different stress paths, reduced triaxial compression (RTC) and reduced triaxial extension (RTE), four axial consolidation stress (80kPa, 160kPa, 240kPa and 320kPa), and three stress rate (0.02 kPa/min, 0.2kPa/min and 2kPa/min) were configured by GDS triaxial system. Based on the experimental data, the relationship among initial tangent modulus Ei, ultimate deviatoric stress qult of expansive soil, consolidation stress, and unloading rate was established. The results showed that the stress-strain relationship of expansive soil was hyperbolic along the unloading paths in both RTC test and RTE test. The shear strength increased as the stress rate and confined pressure increased monotonously. The changes of initial tangent modulus Ei and the ultimate principal stress difference qult were similar to the shear strength. The initial tangent modulus Ei increased exponentially and the ultimate principal stress difference qult increased linearly as the confined pressure increases. Based on the modified Duncan-Chang model, the prediction formula considering the stress rate was built for expansive soil under K0 consolidation condition.

Bucket foundations are widely used in ocean engineering. The determination of the penetration resistance is a key to the successful application of this type of foundation. In ocean engineering, the properties of silt is largely different from sand and clay. But the existing calculation method of penetration resistance of bucket foundation is generally for sandy soil, which neglects the influence of the cohesion c on the penetration resistance. In this paper, three bucket foundations with different types of tip are penetrated by dead-weight and suction pressure. The relations between penetration resistance and penetration depth are measured in the different penetration stages by dead-weight and by suction. Two methods for calculating the penetration resistance of bucket foundation in silt were derived. The effect of drag reduction in different tips were analyzed. Studies have shown that the calculation value of the penetration resistance of bucket foundation by specification in slit is 20% smaller than measured value. Two methods proposed in this paper that can not only accurately calculate the penetration resistance, but also can reflect the drag reduction effect caused by suction. The sharp-tip can reduce the half of the tip resistance and the anti-drag ring reduce the half friction resistance. However, the anti-drag ring will destroy the soil around the wall and formed a seepage channel, which fail to provide the penetration force.

When the natural soil is influenced by the unloading induced by the excavation, its stress-strain relationship shows a quite difference with the relationships obtain from the conventional loading test of undisturbed natural soil. At present, commonly applied soil constitutive models are established based on the conventional tri-axial test, where soil is subjected to isotropic confine pressure and uni-axial loading stress. In addition, these constitutive models do not take the influence of initial K0 consolidation and the unloading induced by excavation into consideration. In this paper, a new model is proposed based on the Cam-clay model and the principles of Ohta-Sekiguchi model. In the proposed model, to adjust the elastic region and reflect the influence of the initial K0 consolidation, the hardening axis in p–q stress space is rotated by introducing a stress ratio. To describe the three-dimensional anisotropic stress state, the transformation stress method is introduced to the model. By all these approaches above, this newly proposed model is able to reasonably describe the strength and deformation of soil under initial K0 stress and complex stress-train relationships under unloading induced by excavation. The rationality of this proposed model is verified by comparing the predicted results with the results obtained from typical laboratory tests.

The dynamic characteristics of X-section cast-in-situ concrete (XCC) pile-geogrid composite foundation under half sine wave loading simulating different static and dynamic loads from a moving vehicle axle are investigated in large-scale model tests. The dynamic stress of an XCC pile, soil arching, dynamic soil pressure, the stress transfer coefficient of the cushion, dynamic strain of the geogrid are analyzed. The mechanism of XCC pile-geogrid composite foundation influenced by the static and dynamic loads of vehicles is preliminarily revealed. The test results show that the influence depth of dynamic loads on stress of an XCC pile is 2 meters. More dynamic stresses are supported by the soil between piles and the effect of a geogrid on the road shoulder is weakened with the increasing of the static and dynamic loads. The stress transfer coefficient of the cushion located in the center of subgrade is constant with the increasing of the static and dynamic loads. The cumulative deformation of a geogrid increases rapidly with the increasing of the static and dynamic loads as the value of the ratio of dynamic strain is over 0.048.

The rockburst experiments were conducted on red coarse-grain granites with different water saturations by using true triaxial rockburst test system. Then this study analyzed the characteristics of strength and deformation, damage and ejection process, failure mode and acoustic emission (AE) of rock specimens after rockburst with different water saturations. The relationship between the water saturation and kinetic energy of rockburst ejection and the influence mechanism of water on rockburst were discussed as well. The results showed that when the water saturation of specimens exceeded 0.3, the peak stress and yield stress of the specimens were significantly lower than those of natural specimens. With the increasing of water saturation, the ejecting behavior of small particles decreased, the spalling behavior of small rock slices increased, and the bulging behavior of rock plates weakened during the process of rockburst. Moreover, the volume of rockburst pits decreased, and the particle-size distribution of rockburst fragments became discontinuous. With the increasing of water saturation, the duration of ‘quiet period’ decreased, in which AE impact number dropped significantly before rockburst. Besides, the AE impact number increased at the moment of rockburst, while the accumulated absolute energy and the energy release rate declined, which indicated that the plastic failure of specimen enhanced. The rockburst kinetic energy of specimens decreased obviously with the increasing of water saturation, which exhibited a monotonous linear relationship between the kinetic energy and water saturation. Water mainly showed softening and water wedge effects on rock, and the viscosity of water also affected the ejection of rock fragments.

Considering the universal existance of damaged rock mass in the actual environment, the typical sandstone was selected to investigate the creep and saturation induced damage. The damage variable analysis and calculationunder different influence factors were carried out. Based on unloading failure tests on damaged sandstone samples under different influence factors, the morphological characteristics of the unloading failure surfaces were compared and analyzed by using ST400 type 3D surface topography instrument, and the influencing mechanism of creep and saturation induced damage on the morphology of the unloading failure surface was discussed. The damage variable analysis shows that the elastic modulus method can well reflect the damage degree under different influence factors, while the ultrasonic detection method is sensitive to saturation and incapable to describe the damage degree of sandstone after creep and saturation. Morphology characteristic and fractal characteristic of the unloading failure surfaces from specimens with different damage degree show that the creep and saturation damage increases the overall roughness of the unloading failure surface, which makes the dispersion and fluctuation of the failure surface become larger. Meanwhile, the creep and saturation damage results in low roughness and obvious anisotropy of the failure surface and the fractal dimension decreases first and then increases with the damage changes from negative to positive. Compared analysis of two group specimens shows that saturation after creep damage has no significant influence on morphological characteristics of the unloading failure surface, which means that creep damage is the main influence factor.

A series of soil water characteristic curve tests and triaxial shear tests were carried out on different structural unsaturated compacted loess samples after increasing or decreasing moisture to the same water content and dry density. The influence of different structures caused by the change of molding water content on matric suction and stress-strain characteristics as well as the structural parameter was investigated for the unsaturated compacted loess. The results indicate that the structure caused by the molding water content has a obvious effect on the soil water characteristic curve of unsaturated compacted loess. The matric suction increases with the increase of the molding water content when it is less than plastic limit. The compacted loess, which has the agglomerate structure with uniform pore size, results in relatively maximum suction at its best water content. The stress-strain curve of sample with optimum structure state is at the top of the coordinate. The degree of structural weakening is relative lighter when the water conent is less than the optimum molding water content, resulting in the stress-strain curve moves downward gradually. On contrarily, when the water conent is higher than the optimum molding water content, the degree of structural weakening is relative higher, which makes the stress-strain curve at the bottom. The proposed parameter m?r can reasonably reflect the structure of compacted loess, which overcomes the deficiency that the optimum moisture content and maximum dry density indexes cannot reflect the influence of soil structure in compacted soil engineering. The yield structural parameter m?r0 can reasonably reflect the degree of structural weakening of compacted loess with different molding water contents, and the degree of structural weakening is also reflected in the triaxial shear failure strength.

The damage of brittle rock is induced by its microcrack growth which significantly affects the deformation and strength of rocks subjected to the compressive loadings. However, the relationships between microcrack growth and the variable shear properties (cohesion, internal friction angle, and shear stress) are rarely studied. In this study, the relationships between internal friction angle, cohesion, shear strength and micro-parameters at the peak point of stress-strain relationship are proposed, according to the stress-strain relationship triggered by crack growth and the Mohr-Coulomb failure criterion. By introducing the Mohr-Coulomb yield criterion, the theoretical expression is established for dynamic variations of cohesion, internal friction angle and shear stress along with microcrack growth or strain at plastic deformation phase of brittle rocks. Cohesion, internal friction angle, and shear stress firstly increase until to maximum values, and then decrease with the increasing crack growth or axial strain in brittle rocks under compressive loading, which is corresponding to the stress-strain constitutive curves in triaxial compressive tests. Finally, the rationality of the proposed theoretical expression is verified by comparing with the experimental results. Besides, the effects of friction coefficient between microcrack interfaces on the relationships between cohesion, internal friction angle, shear stress and crack growth or axial strain are discussed.

Based on the theory of correlation function, a new method for calculating the dynamic modulus and damping ratio of dynamic triaxial test is proposed. Based on viscoelastic constitutive model, the amplitudes of strain and stress can be captured by analyzing the autocorrelative function of strain and stress variations with time, respectively. Thus, the dynamic modulus can be calculated. The damping ratio is determined through the characterization of the phase lag between the strain and stress time-histories which can be captured by the cross-correlation function. A series of undrained multistage strain-controlled cyclic triaxial test was conducted on saturated coral sand, Nanjing fine sand, and a type of undisturbed silty clay. The dynamic modulus and damping ratios were calculated from the experimental results using both the correlation function (CF) method and the conventional hysteresis loop (HL) method. The results show that the CF method is applicable for the calculation of dynamic modulus and damping ratio of different types of soils. The results show that the precision of the CF method for the modulus and damping ratio is significantly higher than that of the HL method within the strain amplitude of 1×10?4. When the strain amplitude is greater than 1×10?3, because of the strong nonlinearity of soil as well as the asymmetry of the stress-strain hysteresis loop, the damping ratio of soil calculated by the CF method is more reliable.

We focus on the weak intercalation of Permian carbonaceous shale and analyze mineral composition, microstructure, and shear creep characteristics of Permian carbonaceous shale under different levels of normal stress during three evolutionary stages: original soft rock, interlayer shear zone, and sliding zone. The analysis results indicate that during the evolutionary process of the weak intercalation stage, the mineral compositions and content of the shale changed, and the clay mineral content gradually increased from less than 5% in the original soft rock stage to 5%-10% in the interlayer shear zone stage, and finally to greater than 10% in the sliding zone stage. The microstructure changed from compact to loose, and the bonding force between the particles was weakened. The creep displacement and the rate increases non-linearly with increasing shear stress. Under identical shear stress, the relationship of the creep displacement and the rate was that the sliding zone was greater than the interlayer shear zone, and the interlayer shear zone was greater than the original soft rock. The long-term shear strength gradually decreased, the drop in cohesion was greater than the angle of internal friction, and the cohesion was more sensitive to time than the angle of internal friction. The conclusions of this paper provided an important reference for the study of the development and mechanism of layered rock landslides controlled by weak intercalations.

The frequency of seismic waves is one of the most important features of ground motion, and the seismic response of the slope under an earthquake is the combined effect of different frequency components of seismic waves on the slope body. The large-scale shaking table tests were conducted on a slope with the horizontal soft interlayer, and the corresponding response spectrum characteristics of horizontal acceleration were analyzed when the slope was subjected to the natural wave (2008 Wenchuan wave) excitations. Firstly, based on the Hilbert-Huang transform method, the original wave data was efficiently denoised and the Hilbert marginal spectrums were obtained using the reconstructed data. According to the marginal spectrums, the horizontal acceleration responses on the slope surface were analyzed in the frequency domain with different elevations and excitation intensities, respectively. Meanwhile, the peak horizontal acceleration response in the time domain were compared with the macro deformation and failure features of the slope. The research results showed that 1) with the increasing elevation, the spectrum amplitude increased accordingly and multiple peaks occurred in the spectral line. The upper part of the slope, especially the slope crest, was very sensitive to the shaking action. With the increasing excitation intensity, the distribution of the concentrated shaking energy gradually changed from two ranges (ie. 7-11 Hz and 15-20 Hz, high frequency) to one range (ie.7-11 Hz, low frequency). 2) when the excitation intensity increased from 0.2 g to 0.5 g, both the first and the second dominant frequencies (separately corresponding to the first largest and the second largest spectrum amplitude) demonstrated irregular fluctuations within a wide zone. This indicates there was a deterioration of the inner slope structure during this loading phase, but without the macroscopic deformation. 3) with the increasing elevation and the excitation intensity, the change law of the peak horizontal acceleration was similar to the change law of the first largest spectrum amplitude, but locally influenced by the second largest spectrum amplitude response. 4) in the low frequency (<5 Hz) range, an obvious weak response zone appeared in and around the soft interlayer (relative elevation is 0.25-0.75). Moreover, the shape and value of the spectrums irregularly varied in the zone. 5) the deformation and failure process was clearly controlled by the slope surface rather than the slope crest. A ‘resonance elevation’ should exist where makes the maximum response occur due to the interaction effect of the seismic waves and the slope body. Besides, this elevation is consistent with the estimated one by using the second dominant frequency (16 Hz) as the resonance frequency.

Combined with the assumption of normal stress distribution on sliding surface and the spatial analysis capability of Geographic Information Systems (GIS), a three-dimensional (3D) slope equilibrium model based on grid cells is established, and a GIS-based slope stability calculation method is proposed. In this method, a 3D slope stability analysis model based on grid cylinder elements is firstly established, and the spatial computational expression of each parameter in GIS is clearly articulated. Secondly, under the condition of limit equilibrium, a set of stability analysis equations, including three force equilibrium equations and one moment equilibrium equation of the sliding body, are derived for solving the three-dimensional safety factor. Finally, following the Mohr-Coulomb strength criterion and the assumption of normal stress distribution on the sliding surface, the three-dimensional safety factor is solved. Moreover, the component object model (COM) technology is used to develop a GIS-based 3D slope stability analysis module, which can be implemented for the complex algorithms and the calculation of multiple stratigraphic slopes and multiple combinations of factors in 3D slope stability analyses. The correctness and feasibility of the module are verified by three typical cases.

Deep rock mass is a block-hierarchical structure. Dynamic events cause rock mass to be separated from each other during wave propagation, resulting in a low friction effect, which can easily induce the large dynamic deformation of the rock mass in the equilibrium state. Based on the previous studies, the vibration system of rock block is simplified as the equivalent mass-viscoelastic model, and the slip rate weakening mode of the rock friction is introduced. Finally, the calculation model of rock block slip is obtained. The effects of viscoelasticity property of soft medium between rock blocks and the external loads on the relative displacement of the working rock blocks are analyzed. Calculation results show that when the elastic coefficient increases or the cohesive coefficient decreases, the low friction slipping is more likely to occur. With the increase of the external disturbance or horizontal force, the horizontal residual displacement of the rock block increases, and when their amplitudes exceed a critical value, the sustained sliding instability occurs. The critical energy triggering irreversible displacement and dynamic sliding instability is closely related to the value of shear force. With large enough shear force, extremely weak disturbances can induce large irreversible displacement or even dynamic sliding instability between rock blocks, while a greater impact disturbance is required with smaller shear force. When the shear force drops to a value lower than the dynamic friction strength, a single impact load cannot induce dynamic sliding instability but only irreversible displacement. The horizontal dynamic response of the purple sandstone block under the combined effect of vertical impact load and horizontal static force is measured. The experimental results are basically consistent with the theoretical calculation, which proves the feasibility of the model.

The varying cyclic confined pressures will aggravate the pore water pressure and the accumulated plastic strain of soil and even lead to the catastrophic accident. The triaxial tests with cyclic confining pressure were carried out to study the pore pressure, the axial cumulative plastic strain and the volumetric strain of saturated silty clay under different stress paths and cyclic dynamic stress ratios by using GDS triaxial apparatus under partial drained conditions. A mathematical model of accumulated strain for silty clay under cyclic confining pressure and cyclic dynamic stress was established under partial drainage conditions. The experimental results show that the pore water pressure, axial cumulative plastic strain and volumetric strain of the saturated silty clay increase as the cyclic dynamic stress ratio and the stress path slope increases. The dynamic pore pressure ratio versus vibration number curves divided into three stages: rapid increase stage, rapid decline stage and sustained stability stage, respectively. The axial cumulative plastic strain and volumetric strain increase as the vibration number increases. The pore pressure of silty clay tends to be stable, while the deformation rate decreases slightly, but the deformation increases continuously when the number of loading is more than 2 500 times. The supplementary experimental results show that the established model is in good agreement with the experimental results. The results will provide a theoretical basis for the foundation disaster control technology caused by traffic cycle load.

Due to the large deformation and its long time dependent characteristic of high rockfill dams, a method of using composite grout to increase the compression modulus and reduce creep deformation of rockfill materials is proposed for high rockfill dams. The composite grout is a mixture of fly ash and cement with the characteristics of easy flow and post hardening. The composite grout was first sprinkled on the surface of rockfills, which later infiltrated into the rockfills during the process of rolling compaction. Flow tests on glass balls were conducted to study the effects of mixture ratios and contents of composite grout on its flow characteristics. Confined compression tests and creep tests were finally carried out to investigate the compression modulus and creep deformation of rockfills with composite grout. The results show that the flow property of composite grout is related to the fly ash content, water-to-binder ratio, maximum sand size and mixed content. The filling of composite grout can effectively increase the compression modulus and decrease creep deformation of rockfills, especially for soft rock materials and poorly-graded rockfills. The composite grout mainly plays the role of filling, cementation and lubrication in rockfills.

Reinforced soil retaining walls are increasingly favored by designers in civil engineering because of its unique landscape performance and good seismic-resistance performance. As an integral part of the reinforced soil retaining walls, facing has a significant influence on its bearing capacity. In view of the fact that the existing design codes cannot consider the effect of facing form on the mechanical deformation characteristics of the structure itself, centrifuge model tests were carried out on walls with full-height panel facing and blocked facing. The following results are obtained: the displacement of the full-height panel facing is less than that of the blocked facing during the loading period. Since the larger displacement for the model wall with blocked facing, its horizontal earth pressure is smaller; stress concentration occurs at the bottom of the facing of the reinforced soil retaining wall. It is found that the soil-reinforcement friction coefficient for the reinforced soil retaining wall with blocked facing is larger than that in the case of full-height panel facing, while both of them are less than the recommended values from the design codes. The model walls are conservative due to the larger reinforcement length and the use of the anchor connector.

In practical engineering, the foundation is usually untreated, natural and heterogeneous. The phenomenon that threshold hydraulic gradient exists in clayey soil under low hydraulic gradient is gradually recognized. However, the consolidation model of heterogeneous foundations considering threshold hydraulic gradient is rarely reported. In this paper, based on seepage model considering threshold hydraulic gradient, the consolidation problem of heterogeneous foundation was studied, the change law of compressive modulus and permeability coefficient with depth under variable loads were obtained. One-dimensional consolidation model of single-layer heterogeneous foundation was established with an assumption that the compression modulus increases with depth, and the permeability coefficient decreases with depth. The influence of threshold hydraulic gradient i0, heterogeneous foundation parameter ?, x, ? and p on the consolidation characteristics of heterogeneous foundation were analyzed. The results show that, the rate of pore pressure dissipation becomes slower in heterogeneous foundation after considering threshold hydraulic gradient and settlement as well as consolidation rate of the foundation decreases accordingly. The consolidation rate is directly proportional to the value of ? and x while the final settlement of the foundation comes inversely proportional to them. The consolidation rate grows with the increase of ? and the decrease of p. However, the permeability coefficient may only change the settlement rate of foundation, which will not affect the final settlement of the heterogeneous foundations.

Considering the influence of the volumetric behavior on the soil state, a void-ratio-dependent shear strength criterion for unsaturated soils is proposed by introducing the state surface expression into the Vanapalli’s shear strength equation. The saturated shear strength parameters and two series of soil water characteristic curve (SWCC) corresponding to different void ratios are employed in the proposed criterion. A series of SWCC tests, isotropic compression tests and suction-controlled triaxial tests are performed on a soil mixture of tailing sand and speswhite China kaolin. The testing results indicate that the proposed criterion can provide a more accurate prediction of shear strength for unsaturated soils than that of convention prediction using a unique SWCC. It is proved that the principal source of errors in the conventional estimation of shear strength is related to the evolution of soil state caused by the volume change. Moreover, a method for accurately identifying the failure envelopes in different stress spaces is developed. Several mechanical characteristics of unsaturated soils, including an increase in the slope of failure envelope with suction in net stress versus shear strength plane and the influence of the net stress on the shape of the failure envelope in the suction-strength plane, are reasonably interpreted by this method.

According to the fact that of some water in soil cannot be frozen due to distribution of cationic diffusion layer on the surface of negatively charged clay particles, the theoretical formula of unfrozen water content is obtained by electrical double-layer theory based on Poisson equation of electrostatic field and static charge Boltzmann distribution. the empirical formula of classical unfrozen water content is almost identical to the proposed model. This paper describes the structure and causes of unfrozen water on the surface of soil particles, and quantitatively analyzes the effect of soil type, salinity and temperature on unfrozen water content. When the soil salt concentration is less than a threshold value, changes in salinity negligibly influence the unfrozen water content. This indicated different types of frozen soil texture (low salinity) have analogous structure of electric double layer. the empirical formula of exponential form can describe all unfrozen water content of low salinity frozen soil. The unfrozen water content is dependent on soil types, specific surface area. More clay particles in soil and larger specific surface area resulted in more unfrozen water content. Two existing empirical formulas have been used to verify the theoretical formula. Results prove that the theoretical formula for calculating unfrozen water content in frozen soil is reliable.

In order to investigate the impacts of fine content FC, relative density Dr and initial effective confining pressure on the shear wave velocity Vs of sand-silt mixtures, a series of bender element tests was performed on saturated sand-silt mixtures with different FC, Dr and . The test results show that Vs of loose and medium-dense mixtures firstly decreases and then increases as FC increases, while Vs of dense mixtures presents a trend of decreasing. At a fixed FC, the Vs of the mixtures decreases monotonically with the increase of the consoildated void ratio ec, but there is no a single negative linear relationship between Vs and ec of different FC mixtures. It is found that the Vs of mixtures with different FC, Dr and decreases monotonically with the increase of the equivalent skeleton void ratio esk*. The test data of three types of sand-silt mixtures in the literature also support this conclusion. The test results show that esk* is the only physical state index with negative linear correlation with Vs of sand-silt mixtures.

It is of great practical value to know the degradation process of coarse-grained soil particles, but the research on predicting the process of particle gradation has not been sufficiently executed yet. To compensate this insufficiency, the study on predicting model for coarse-grained soil particle breakage process was carried out using logarithmic probability regression mathematic method. Based on the probability theory, a logarithmic probability regression method was first set up to simulate the particle gradation process of coarse-grained soil in integral distribution curve frame. And then, a ratio of survival probability to death probability (also called breakage probability) was introduced into this setup logarithmic probability regression method to develop a prediction model for the coarse-grained soil particle degradation. The sensitivity analysis of the predicting model parameters was presented, and the degradation imitation for coarse-grained soil was discussed in the frame system of integral distribution curves. After that, a new formula to calculate the Hardin relative particle breakage index was presented to replace traditional formula for Hardin relative particle breakage index. The new model was applied to predict the coarse-grained soil particle breakage process of several experimental data reported by other authors. Application results show that the model-predicted integral distribution curves were very close to the experimental integral distribution curves. The good agreement between the predicted particle breakage process and the tested particle breakage process verifies the feasibility of this predicting model for coarse-grained soil particle breakage process. The results of this study are helpful for the understanding of particle evolution of coarse-grained soil with intermediate process.

The hydraulic fracturing (HF) behavior under CO2 condition is a key scientific issue in CO2-enhanced geothermal system project. The granite specimen was taken from the quarry in Zhangzhou, Fujian province. HF experiments were conducted to investigate the effects of CO2 and H2O on the HF process and crack propagation by using a new independently developed hollow cylinder. This study reveals that with the decrease of the viscosity of the fracturing fluid, a greater number and more sinuous microcrack branches form in the fracture process. This indicates that CO2 fracturing may be more conducive to the formation of the crack network, which helps to increase the heat exchange efficiency in the CO2-EGS projects. The fracture pressure of the specimen decreases with decreasing the viscosity of the fracturing fluid, which leads to the safe operation of the injection well with a lower value. The experimental results consist with the interaction mechanism of fluid rock from the convective heat transfer perspective, and its accuracy is verified.

This paper has performed a group of undrained unidirectional cyclic loading tests on undisturbed clay samples near planned metro line of Hangzhou. To simulate subway load, this paper has considered the characteristic that the trains always leave at intervals, so cyclic load is designed to consider regular intervals. Under cyclic loading with different amplitudes, dynamic loading durations and intervals durations, excess pore water pressure accumulations are observed. In this paper, the critical dynamic amplitude under cyclic loading with intervals is obtained and is found to be similar with that under cyclic loading without intervals. After that, an explicit model to calculate excess pore water pressure is built with an independent variable that describes cumulative dynamic deviator stress level. It is a new stress state parameter that can describe the effect of long-term dynamic loading in a cumulative way. The influence regulation of cumulative dynamic deviator stress level, vibration number and interval duration are presented and the dynamic deviator stress level and vibration number are much more important to excess pore water pressure accumulation than intervals. This explicit model is in the form of hyperbolic function with one major variable and a few constants. When predicting excess pore water pressure under different vibration numbers, these constants are also different but has relation with vibration number. The method to calculate the constants is also presented. In the end of this paper, testing results of several samples are presented to verify this model. Comparing the results predicted by the new model with an existing model with the measured data, the new model performs well.

This study is aimed to analyze the seismic wave response of coal and rock induced by the mining and the corresponding characteristics of wave field. Multi-channel microseismic monitoring system was installed for monitoring the propagation of the mining seismic wave in the rock roof and coal seam. Then the propagation and attenuation characteristics of mining seismic waves in two propagation media were further analyzed. Research results indicate the average velocity and acceleration of the mining seismic wave received by the rock roof are higher than those received by the coal seam. The accelerations of mining seismic waves in two media were both proportional to the explosive charge, but negatively correlated with propagation distance and medium density. The energy and signal duration of the mining micro-seismic wave showed exponential and linear attenuations with the propagation distance, respectively. The energy and signal duration in the coal seam near the explosive center were higher than those in the roof, while the energy and signal duration in the roof were higher than those in the coal seam after a certain propagation distance. The propagation distance of mining micro-seismic wave was limited, and the effective propagation distance in the roof was higher than that in the coal seam. Meanwhile, the effective seismic wave propagation distance was linearly and positively correlated with the explosive charge. The quality factors of the low frequency part of the mining seismic waves were higher than those of the high frequency part, and quality factors of the rock roof were higher than those of the coal seam. The research results contribute to the selection of the seismic wave propagation medium and optimization of the detector layout.

The uplift piles in soft rock with shallow overburden are common in the design of tower foundation of transmission line projects in western China, but there are relatively few studies on the uplift piles at present. The choice of pile side friction resistance value in soft rock in current codes needs to be improved. In this study, field tests in the south side of the Qingjiang river in Guangyuan City were conducted to investigate the bearing performance of 5 uplift piles. By analyzing the Q-s curve, the axial force distribution of pile shaft and the exertion of pile side friction, the standard values of pile side ultimate friction of severely weathered sandstone and weathered sandstone were obtained. The relationship between the average ultimate friction resistance and the uniaxial compressive strength (UCS) of the soft sandstone was obtained as well. A formula to predict the ultimate bearing capacity of an uplift pile was also proposed. In addition, comparison was made between the field test measurements and the value calculated using the existing standards. Our study found an exponential relation between the average side resistance of piles and the UCS of soft sandstone. The standard values of the ultimate side friction found in heavily and medium weathered sandstones were 472 kPa and 1,027 kPa, respectively. This finding provides an engineering reference for future projects.

Based on the characteristics of low frequency periodic pulse pressure, a new method was proposed for seepage control and reinforcement of a dam. A prototype test of a manmade homogeneous embankment demonstrated that the method, considering drilling disturbances and repetitive pulsating pressure on the permeability of strata, was feasible. The clay-cement slurry pulsation diffusion equation was determined using the multi-coupling software COMSOL to investigate the mechanism of fluctuating pressure under the clay-cement slurry diffusion. Finally, this research was successfully applied to the Hebi section of the middle route water diversion channel along the grout curtain slope. The results showed that the 28-day strength of stone was greater than 2 MPa and the permeability coefficient was reduced to approximately 10?5 cm/s, demonstrating that the clay-cement slurry pulsation control grouting technology can significantly improve the stratigraphic continuity. Observations were made on the slurry in the grouting hole near the soil and cement block, the adjacent grouting hole slurry vein staggered lap joint, and the overall performance of the impervious wall space of the three-dimensional structure. Based on a comprehensive analysis of the numerical simulation and the field test results, the dam grouting time fluctuation should remain between 1 800 s and 2 400 s, a reasonable grouting pressure pulsation should be between 0.2 MPa and 2 MPa, the pulse duration should be between 4 s and 8 s, and the pulse interval time should be adjusted to between 2 s and 6 s. These values ensure that the seepage and the reinforcement of the dam grouting remain in optimal engineering ranges. The channel slope continuity and integrity were improved, and significant improvement was noted for grout reinforcement sealing. The coefficient was reduced to 10?5 cm/s, and the core sample remained as a whole with the length up to 40 cm.

In order to obtain a deeper understanding of the deformation characteristics of the retaining structure and the adjacent buildings of deep foundation pit of metro station caused by deep excavation in soft soil, systematic monitoring and result analysis of deep foundation pit engineering of a metro station in deep soft clay area were carried out. It was found that grooving of diaphragm wall will cause lateral displacement of adjacent soil. The maximum lateral displacement of soil accounts for about 20% of the lateral displacement of soil during excavation of foundation pit. The average values of maximum lateral displacement of the retaining wall on the south side (namely the side of the pile foundation buildings) and the north side (namely the side of the shallow foundation buildings) during soil excavation were 0.091% He and 0.120% He, respectively. When the value of y/He ( y is the distance between vertical continuous wall direction and diaphragm wall, and He is the excavation depth) is less than 0.92, the magnitude of the settlement and differential settlement induced by excavation was relatively larger. The settlement of the ground surface was close to that of the shallow foundation settlement, while the settlement of the pile foundation was obviously less than that of the shallow foundation building among which the rock-socketed pile foundation building had the smallest deformation value. Both the shallow foundation buildings and pile foundation buildings were affected by spatial effect which was more obvious when the value of x/He (x, the distance from the corner in the longitudinal direction) was less than 1.5. When the value of x/He was greater than 2.0, the soil deformation near the adjacent buildings and retaining structures approached to a plane strain state.

The underground rock mass condition is very complex. Therefore, the deficiency of seepage monitoring data exists. To comprehensively analyze the underground seepage field in time and space, it is necessary to replenish the missing data. Three types of supplement methods of missing data are proposed: missing data in time sequence can be replenished by creating monitoring statistic model; missing data on spatial sections can be supplemented by regression analysis modified by physical factors; missing data in the whole area can be replenished by back analysis calculation. All these can reflect the regulation of missing data and the influence of chronological and spatial factors on measuring data. Integrated and comprehensive seepage field is obtained, by which seepage stability can be determined, providing reference to project evaluation. These methods are used in Tianhuangping power station. The results show that the complementary piezometric heads and flow rates are in good agreement with the measured data, the back-analyzed seepage field conforms to the engineering practice, and the locations where seepage failure may happen are effectively determined by the back-calculated field. Engineering suggestions are proposed based on the seepage stability, which has instructive meaning to project reinforcement.

The aquitard hydraulic parameters are important for basic engineering design, construction, groundwater resource evaluation and groundwater pollution prediction. A new method of borehole double-tube test is proposed to estimate the hydraulic parameters of aquitard in aquifer system, including vertical hydraulic conductivity K and specific storage μs. The drill pipe is drilled below the water level line by auger drill, and the outer pipe is laid after the target layer is exposed, so as to protect the wall and prevent the collapse of the soil layer. In the outer pipe, the inner pipe is embedded into the target layer by hammering, and the soil sample with a certain thickness in the inner pipe is used as the fixed soil column in the field test. Then the water is injected into the inner pipe rapidly when the groundwater level in the inner and outer pipe is stable, at the same time, and the fixed head is maintained through the Mariot bottle device. A mathematical model of soil column in borehole double-tube test is established, and the analytical solution of unit area flow rate of top and bottom of soil column with time is deduced. The dimensionless analytical solution is derived and the standard curve is obtained. As an example of the application for this method, a special borehole test was carried out in the open field near De'an Hospital, Tianning District, Changzhou, in the alluvial plain of Suzhou-Wuxi-Changzhou, the lower Yangtze River Delta. The hydraulic conductivity and the specific storage of fine sandy silt and silty clay in this area are determined as follows: K=1.66×10?6 m/s, ?s =8.21×10?3 m?1；K=6.06×10?7 m/s, ?s =2.26×10?3 m?1, respectively, which demonstrates that the method has good applicability for determining the hydraulic parameters of aquitard in the field.

Due to the existence of high geostress and high geotemperature, the rockburst disaster is highly possible during the excavation of the newly-built Sangzhuling tunnel in the lasa-Nyingchi project. According to the unloading-temperature drop coupling action, the numerical model was conducted to simulate the stress release process during the tunnel excavation at different temperatures. At the same time, the secondary stress field was measured on site. The influence of high geotemperature on the circumferential stress was comparatively analyzed. Finally, the effect of high geotemperature on rockburst occurrence was discussed by considering different criteria. The results show that the indices of stress release rate and large temperature drop are used to reflect the excavation unloading-temperature drop coupling function, which can reasonably describe stress characteristics and rockburst occurrence law under high-geostress and high geotemperature in the excavation process. When the temperature drop exceeds 55 ℃ and the stress release coefficient is greater than 40%, and linearly increase with the increase of stress release coefficient. The and achieve maximum values when the stress release rate reaches 100%. It is found that the stress at the arch foot increases fastest, following at the vault. With the increase of the stress release coefficient, the rockburst occurs earlier due to the high geotemperature, and the grade of rock burst also increases.

On the basis of construction of the No.29 open caisson of Hutong Bridge, which is the largest open caisson in the world, in-site monitoring tests were carried out on the entire process of the open caisson construction. By analyzing the monitoring data, it is concluded that results predicted by Rankine's theory of stationary earth pressure and its normative algorithm are significantly different from the measured data. The result of polyline distribution projection is not satisfactory because there are many influencing factors of lateral pressure and its distribution is complicated. Then, the influencing factors on the size and distribution of lateral pressure during the sinking and subsequent construction of caisson are studied. It is concluded that the main influencing factors of the lateral pressure during the sinking stage and the heightening stage are the slant of caisson, the depth of caisson, the step setting of caisson sidewall and the range of pressure relaxation. The causes and mechanism of various factors are explained based on comparison and analysis. The distribution of lateral pressure along the vertical caisson sidewall and the side frictional resistance calculation model are determined after eliminating the effect of the caisson slant on the lateral pressure of the ultra-deep large and subaqueous open caisson.

A two-dimensional finite element calculation model of subgrade-hill under the vibration of train is established, and the influence of the width, shape, aspect ratio of hill and soil properties on railway environmental vibration is studied. The result shows that the ground acceleration of railway environmental vibration is reduced, but the horizontal vibration displacement is significantly amplified, and the influence on vertical vibration displacement is not obvious. With the increase of the width and aspect ratio of the hill, the amplification effect of horizontal vibration displacement becomes notable. The larger the aspect ratio is, the more obvious the vertical and horizontal ground accelerations decrease. The influence of semicircular and trapezoidal hill on railway environmental vibration is consistent, but the horizontal acceleration at the top of the triangular hill is locally amplified, and the amplification effect of horizontal vibration displacement is more obvious than that of the trapezoidal and semicircular hills. When the soil is soft, the effect of the hill becomes significant.

Due to the complexity of foundation pit supporting structure, frequent occurance of collapse accidents and applicating limitation of traditional fault tree analysis(FTA) methodinduced by probability and accuracy logical relationship, a method for eveluating the foundation pit collapse probability based on T-S fuzzy fault tree is proposed. This method uses fuzzy numbers to describe the probability and fault state of each bottom event, which sloves the problems suffered by traditional fault tree that relies too much on accurate probability and fails to take the intermediate fault state of events into conisderation. At the same time, T-S model is used to replace the traditional logic and/or relationship, which reflects the fuzziness of fault mechanism and event connection, reducing the difficulty of building fault tree. This method can use the actual failure state or the fuzzy probability of the bottom event two different ways to calculate the collapse possibility of foundation pit, which can also guide the risk control work according to the analysis result of bottom event importance. Case analysis shows that this method is more suitable for engineering practice than traditional fault tree. It can scientifically and accurately evaluate the possibility of collapse and determine the key risk factors which can be an effective tool for evaluating the possibility of foundation pit collapse.

Based on the coal mining in Liupanshui area of Guizhou Province, the progressive failure process and failure mode of the slope above a mine-out area were studied by the centrifuge model test and numerical simulation. The displacement fields in mining process were obtained based on the centrifugal model test. Simultaneously, the FLAC3D was used to simulate the centrifugal model test process. The numerical results are in good agreement with the time history curve of the slope displacement obtained from the test results. By comparing the numerical and experimental results, it is shown that the distribution of the plastic zone and the testing points are basically consistent with the failure process of the slip surface. Meanwhile, the glide plane between the through slope toe and the goaf formed from the bottom to the top and it beard shear dislocation failure. The slip surface of the through-slope shoulder and goaf was a complicated failure process from top to bottom: tension failure at initial stage, tensile failure and shear failure simultaneously at middle stage and dramatic shear slip failure at final stage.

Generally, a finite element mesh or a regular mesh is used as the mathematical covering system in the numerical manifold method (NMM). The advantage of the regular mesh is that it has no requirement to conform to the boundary of the solution domain and various discontinuities. In this paper, the regular rectangular mesh was used as the mathematical mesh in NMM, and the analysis-suitable T-spline was introduced into NMM to realize the local refinement. As the analysis-suitable T-spline was defined over a mildly restricted T-mesh, it presents many important mathematical properties, such as linear independence, partition of unity and highly localized refinement capability. However, after an analysis-suitable T-mesh was locally refined, the generated new T-spline was not analysis-suitable. Therefore, a simple local refinement algorithm was developed in this paper to make sure that the refined mathematical mesh was still analysis-suitable. Moreover, the results from numerical examples show that the algorithm has strong applicability in large-stress gradient areas such as stress concentration area and crack tips.

The particle flow code (PFC) was adopted to simulate the cyclic shear test of saturated sand under undrained condition. The influence of different conditions of sand samples on liquefactions was studied. The meso-mechanism of the large limited post-liquefaction deformation was explained by pore distributions. A statistic code was developed to quantify the arrangement of particle and pore, and standard deviation of porosity was proposed to measure the post-liquefaction volume shrinkage potential. Then relationship between the standard deviation of porosity and the limited large post-liquefaction deformation was investigated. It was found that initial conditions have little effect on the ultimate state of post-liquefaction sample, while it only influences the cycle numbers of initial liquefaction. The large limited post-liquefaction deformation on saturated sand in laboratory test repetitively occurs during numerical simulations. The homogenization of pore and the increasement of distance between particles caused by the accumulation of sand volume shrinkage potential was the meso-mechanism of the generation of the large limited post-liquefaction deformation during cyclic shear. As a quantitative index of pore homogenization, standard deviation of porosity got a favorable correlation with the shear strain amplitude in each cycle.

The dynamic stress response of subgrade under moving train loads provides information on subgrade settlement prediction and condition evaluation. In this paper, a 3D dynamic finite element (FE) model, which considered the interaction of wagon-track-subgrade, was firstly built. And then, the vertical irregularity track spectra of China’s three major lines were applied to simulate the track irregularity. Through numerical calculation, the influence of vertical track irregularity on dynamic stress at the subgrade surface was investigated. The distributions of peak dynamic stresses at three locations of subgrade surface (beneath the rails and at the track center) along the track under the passage of the trains with various axle loads were statistically acquired. The normal distributions of peak dynamic stresses on subgrade surface were verified. The maximums of peak dynamic stresses were forecasted. The results indicated that dynamic stresses on the subgrade surface were asymmetric along the center of subgrade surface, attributed by the random distribution of track irregularity. The peak dynamic stresses were found to follow the normal distribution along the track. The dispersion of peak dynamic stresses gradually increased, and the distribution curve of peak dynamic stresses became steeper with the increase of axle load. The computing peak dynamic stresses were consistent with field test data, indicating that the 3D dynamic FE model and statistical analysis method were reasonable. The research results provide the basis for the reliability analysis of the dynamic deformation and accumulated settlement of subgrade.

With the increasing traffic mileage and operation time of tunnels in China, more and more tunnels have entered a period of high disease incidence. Groundwater is one of the most important factors easily causing the water leakage in tunnel lining. In this paper, a three-dimensional geomechanical model test system was developed to investigate the mechanism of the water leakage disease in tunnel lining with different buried depths. The model test system was composed of an extendable model bench, a loading system of ground stress and hydraulic pressure, a multivariate information real-time monitoring system and water leakage real-time measuring device. Using oil jacks and multi-function water pump, the system can simulate the behaviors of tunnels at different buried depths by the stepwise loading method. This model test system was applied to simulate the water leakage in tunnel lining under different buried depths. The evolution law of seepage disease in the tunnel lining crossing cross-fault tunnel under different burial depths was revealed through the analysis of seepage quantity, the seepage pressure and displacement information. At the same time, a preliminarily study was conducted on the combined treatment of blocking and drainage. The positive effect of drainage on reducing the lining seepage quantity was verified. The test results are in good agreement with the results from Kaiyuan tunnel lining seepage disease in operation period. This study proves that the system is stable and reliable, and the research methods and results can provide useful references for related projects.