In order to investigate the dynamic characteristics of reinforced gravel soil under cyclic loading, the consolidated undrained dynamic triaxial tests were carried out on the reinforced gravel soil with different numbers of reinforcement layers and confining pressures. The effects of the number of reinforcement layers and confining pressure on the dynamic characteristics of reinforced gravel soil were studied, and the development mechanism of axial cumulative strain of reinforced gravel soil was further analyzed. The results show that when the number of reinforced layers increases, the axial cumulative strain decreases, the rebound modulus increases, and the influence of reinforcement gradually decreases; when the confining pressure is increased, the axial cumulative strain of the soil decreases, and the rebound modulus and the dynamic pore pressure increase accordingly. As the number of reinforced layers and the number of cycle increase, the hysteresis curve gradually approaches the stress axis, and the hysteresis loop area gradually decreases, and the energy consumption of the soil weakens. Based on the stability theory and the indirect influence band theory, the mechanism of the influence of reinforcement on the development of axial cumulative strain is revealed. An axial cumulative strain prediction model of reinforced gravel soil that accounts for the effect of number of reinforcement layers is established. The parameters ?, ?, ? are linear with the number of reinforcement layers, and the model can effectively predict the deformation of reinforced gravel subgrade under cyclic loading.

The vibration isolation of piles on plane SH waves is simplified to a two-dimensional (2-D) plane problem of elastic wave scattering. Based on the periodic characteristics of the infinite structure in 2-D full-space, an analytical solution for isolation effect of plane SH waves by periodically distributed piles is presented. In the solution, the wave function expansion method together with Graf addition theorem are utilized. Only one periodic element is selected by using the characteristic that the scattering wave field of adjacent periodic elements is one phase different in the frequency domain. Assembling the contribution of the incident wave field and all scattering wave fields, the whole wave fields are obtained by introducing the boundary conditions to determine the unknown coefficients. The analytical solution can accurately solve the scattering problem of infinite periodic distributed piles, and analyze the vibration isolation law when the number of periodic distributed piles is large. It makes up for the shortage that is difficult to solve when there are many piles in the previous theoretical analysis. In this paper, the influences of pile number, pile stiffness, pile spacing and pile type on the vibration isolation effect are discussed. The results show that: 1) The method significantly reduce the amount of storage and calculation in the solving process. The finite period model converges to the infinite period model with the increase of the number of piles, which reflects the correctness of the method. 2) In general, the increase of pile stiffness is beneficial to improve the isolation effect, but it can’t improve vibration isolation effect infinitely. When the shear wave velocity of pile is five times of soil, the isolation effect is enough. 3) The pile spacing has a direct impact on the isolation effect, and reducing the spacing can increase the low frequency band gap width. 4) The type of pile has a significant impact on the isolation effect, the solid pile as a whole has a good isolation effect, and the pipe pile with flexible inner filling has a better isolation effect in the low-frequency segment.

Bedding structural planes play a dominated role in the failure process of carbonaceous slate under loading/unloading conditions. In this work, specimens with the clay mineral rich carbonaceous slate were sampled from Muzhailing tunnel of Shaanxi province in China. A series of Brazilian split tests for the rock specimens was conducted and the corresponding numerical simulations were performed using the cohesive zone model (CZM), in which different bedding angles in the rock were taken into account. This study indicates that the load-displacement relations of the rock specimens with different bedding angles under loads are similar to each other. All of them demonstrates identical basic characters that includes the initial stage, the rock specimens compaction, nearly linear elasticity, and finally complete collapse. The tensile strength of different specimens with bedding angles of 0o, 30o, 45o, 60o, 90o and divider are 1.59, 1.12, 0.89, 0.76, 0.66, 1.65 MPa, respectively. The anisotropy coefficients are 2.41 and 2.50 (divider), and the deterioration of such tensile strength is significantly related to the intrinsic defects and damage due to the water-rock effects. Furthermore, the failure modes and patterns of the rock specimens strongly depend on bedding structures, which can be classified as approximately pure tension failure, shear failure, and mixed tension-shear failure. Additionally, the three-dimensional numerical results show that the predicted split failure processes of carbonaceous slate by the CZM model are in a fair agreement with the results of laboratory tests. Therefore, the fracture mechanical parameters of CZM are valuable for similar tunneling engineering as a reference.

Based on the typical loess plateau slope of Kongtong district, Pingliang city, a 1:25 large-scale shaking table test is designed and accomplished using the conceptual model of the slopes with or without cracks. On the premise of satisfying the similarity principle, the dynamic response characteristics of model slopes of two kinds of structures are analyzed by inputting seismic waves in horizontal direction and vertical direction with different amplitudes. Results show that the horizontal and vertical seismic waves have obvious nonlinear amplification along the slope surface and the internal vertical direction, which reach the maximum value at the top of the slope. Under the horizontal seismic waves with the same amplitude, the acceleration amplification coefficient of the slope surface and section 4 are greater than that of the slope without crack at the same elevation in the middle and upper part of the slope, while in section 1, the amplification coefficient of the crack slope is smaller than that of the crack-free slope. After the seismic wave propagates through the slope soil, the predominant frequency changes significantly. With the increase of elevation, the slope will manifest selective amplification on middle and high frequency bands, which is more obvious on the side of fissure slope. Moreover, as the amplitude of seismic wave increases, the superior frequency transfers to the low frequency direction. However, the remarkable frequency attenuation is not obvious under the vertical seismic wave.

The undrained unloading tests of isotropic consolidation on soft dredger fill of Tianjin Binhai are performed using the stress-path triaxial apparatus to determine the effects of different unloading stress paths and unloading rates on stress-strain relationship, pore pressure variation and failure strength characteristics. Some findings are as follows. The stress-strain curves under each unloading path are approximately hyperbolic curves. Under the unloading stress path of UU0.0(radial unloading, axial not unloading), the deformation of samples exhibits axial compression, and the curves of pore pressure have sharp yield points. On the contrary, the deformation of samples under the path of UU2.0(both axial and radial unloading), UU∞(axial unloading, radial not unloading) and UL1.0(axial unloading, radial loading) show axial tension. In this way, the pore pressure increases with the increase of strain, and finally the growth rate of the pore pressure slows down and tends to increase steadily. Under the same stress paths, the larger the unloading rate, the slower the development of the pore pressure in the initial stage of unloading and the greater the peak pore pressure. The stress-strain curves at unloading rate of 0.1, 0.2 and 0.3 kPa/min are found that the initial tangent modulus is greatly affected by unloading rate under unloading compression paths, while it is not influenced under the tensile paths. The value of unloading failure strength is the maximum under the UL1.0 path, the minimum in the UU2.0 path, and centered in the UU∞ path. Under the same unloading path, the failure strength increases with the increase of the unloading rate. According to the normalization of stress-strain curves, the formulas, which considers the influence of unloading rates and unloading stress paths, are developed to estimate the initial tangent modulus and the unloading failure intensity.

To explore the effect of pore water pressure on shear creep characteristics of rock mass structural planes, an integrated die for fabricating structural planes and a JAW-600 multifunctional shear rheometer were independently developed. The shear creep tests were carried out on serrated structural planes under pore water pressure. The effects of pore water pressure on creep deformation characteristics, creep rate and long-term strength of structural planes were analyzed. The experimental results show that the structural planes under different pore water pressures have experienced instantaneous deformation, deceleration creep and steady creep stages successively, and the increase of pore water pressure promotes the development of the non-linear characteristics of the structural planes; the instantaneous displacement, creep displacement and steady creep rate of the structural planes gradually increase with the increase of pore water pressure, while the creep time, failure stress and long-term strength decrease with the increase of creep strength. According to the test results, considering the influence of pore water pressure on the model parameters, the instantaneous shear modulus, viscous shear modulus and viscous coefficient in the creep model are replaced by the function of pore water pressure, and a structural plane creep model reflecting the influence of pore water pressure is constructed. The model parameters are identified by the optimization analysis software, and the correctness and applicability of the model are verified by comparing the creep test curve with the theoretical model fitting curve. The research results provide some theoretical guidance for the long-term stability analysis of rock mass under the action of groundwater.

Soil freezing characteristic curve (SFCC) defines the relationship between temperature and unfrozen water content. SFCC plays an important role in estimating strength and deformation behavior of frozen soil as well as heat-water transfer in frozen soil. In this work, a new model for SFCC is proposed by explicitly considering capillarity and adsorption. The freezing of pore water is assumed to be dominated by capillarity (i.e., 0～?2 ℃) and adsorption (i.e., <?2 ℃) at high and low temperatures, respectively. The capillarity and adsorption are controlled by soil void ratio and specific surface area, respectively. Extensive experimental data found in the literature (i.e., SFCC with different void ratios; SFCC at wide temperature range; SFCC with different soil specific surface areas) are used to validate the newly proposed model. Three existing models are also adopted to compute the experimental data. Comparisons of the computed results show that only the newly proposed model can capture the void ratio dependent SFCC with one series of parameter. On the other hand, the newly proposed model performs better in computing SFCC at a wide temperature range and those SFCCs with high specific surface areas than those existing models.

Due to the presence of bedded or jointed planes, layered rock mass shows transversely isotropic characteristics in mechanics. Therefore, the existing isotropic creep model is difficult to fully reflect the creep constitutive model of transversely isotropic rock mass. In order to obtain the three-dimensional transversely isotropic creep constitutive model, the Burgers model is adopted to describe the characteristics of instantaneous strain, decaying creep and steady creep of transversely isotropic rock mass. Based on the assumption of constant Poisson’s ratio and three-dimensional isotropic creep constitutive equation, a three-dimensional creep constitutive equation of transversely isotropic rock mass is derived through differential operator method by substitution of transversely isotropic compliance matrix into isotropic compliance matrix. The new model also takes the differences of creep behaviours between specimens with horizontally and vertically oriented bedding into account. According to the characteristics of creep constitutive equation, a method for identifying the creep parameters in the three-dimensional creep constitutive model is proposed based on the creep test results. The model is applied to the identification of triaxial creep test parameters, and a comprehensive set of three-dimensional creep parameters are obtained. The rationality of the proposed creep equation is verified by comparing theoretical values with experiment results. The limitations of the traditional creep tests design scheme are further pointed out and some suggestions for creep tests design of transversely isotropic materials are given. The research results provide a new insight for the study of three-dimensional creep mechanism of rock mass and provide scientific support for the design of rock mass creep tests.

The argillaceous slate obviously shows softening characteristics under water-rock interaction. The relationship between the uniaxial compressive strength (UCS), elastic modulus, Poisson’s ratio and water absorption time in the softening process of argillaceous slate is analyzed by conducting uniaxial compression tests. The laws of pore generation, expansion and breakthrough in the softening process under water-rock interaction are studied by using the nuclear magnetic resonance (NMR). The relationship between porosity and water absorption time in the softening process is analyzed. The evolution rule of microstructure in the softening process of argillaceous slate under water-rock interaction is analyzed by the scanning electron microscope (SEM). Based on the fractal theory, the change rule of the fractal dimension under different soaking time is studied. The fractal dimension value of pore microstructure, porosity, UCS and elastic modulus are selected as the changes of describing the interaction system of argillaceous slate and water solution by using the nonlinear dynamics theory. The applicability of the model is verified with experimental data. The results show that UCS and elastic modulus decrease with the increase of water absorption time, showing a negative linear correlation, but there is no obvious relationship between the Poisson’s ratio and water absorption time. At the early stage of immersion, the water-rock interaction is strong, and the micropores in the slate expand and penetrate to form larger pores, and the porosity increases rapidly. With the increase of water absorption time, the pores in the argillaceous slate are connected with each other to form large pores, which leads to the complex network structure. The fractal dimension of argillaceous slate increases logarithmically and tends to be stable gradually. The results calculated by the nonlinear model are close to the experimental data, which shows that the softening process of argillaceous slate has the obvious nonlinear dynamic characteristics, and the softening law of argillaceous slate under water-rock interaction can be better characterized by the nonlinear dynamic model. The results can provide a reference for the theoretical study of soft rock-water interaction.

The penetration and extraction process of the spudcan of jack-up drilling platform may adversely affect the spudcan of the adjacent wellhead platform. The effect of soil strength and the influenced region after the penetration and extraction of spudcan were examined by performing the model tests and the theoretical analysis. A theoretical method for calculating the bearing capacity of an adjacent spudcan within the influenced region of the spudcan penetration and extraction is developed and compared with the model test results. The results demonstrate that, the relative compaction of sand is reduced after spudcan penetration and extraction, and the rate of reduction gradually decreases with increasing distance to the spudcan. The influenced region of the surrounding soil is approximately one times the diameter of the spudcan. The bearing capacity of adjacent spudcan is reduced due to the spudcan penetration and extraction, and the reduction rate of the bearing capacity decreases as the relative distance between two spudcans increases and increases as the relative penetration depth between two spudcans increases. When the relative distance between two spudcans is greater than 2 times the diameter of the spudcan, it can be considered that the spudcan penetration and extraction have no effect on the bearing capacity of the adjacent spudcan foundation.

The coarse-grained soil is prone to particle breakage under external loads and other factors. A series of single-particle fragmentation tests is conducted for mudstone and sandstone particles. Based on the size effect and fractal model of particle fragmentation, the relationships between the fractal dimension and single-particle crushing strength, fragmentation energy, and Weibull modulus are investigated. A single particle crushing process is analyzed using PFC3D and the modelling results are compared with that from the experimental data to verify the reliability of numerical code. The crushing strength and crushing energy of large particle size are then analyzed by numerical models. The results show that the fractal dimensions of different materials are different under the same test conditions. The fragmentation degree of sandstone with different grain sizes is greater than that of mudstone. The crushing strength of a single particle has an obvious size effect. In addition, the crushing strength and energy of single particle can be predicted by fractal dimension and particle size. The modified Weibull modulus can be also predicted by fractal dimension. The numerical simulation results agree with the experimental results and also agree with the predicted results. Besides, the modelling results of the single particle crushing strength with large particle size are also consistent with the predicted results. The crushing energy, however, shows slightly different, which requires further experimental verification. The research results can provide a reference for obtaining the single particle strength and deformation characteristics of large-size coarse-grained soil.

The existing research on foundation pit mainly focuses on the deformation caused by soil excavation. It is often believed that the retaining wall deformation would commence after soil excavation. However, some field measurements show that the dewatering conducted before soil excavation might have already induced retaining wall deflection and surrounding ground deformation, which could be at centimeter level. Apparently, the monitoring data excluding deformations caused before excavation will underestimate the environmental effect of the construction work. In order to investigate the mechanism of foundation pit deformation caused by dewatering before excavation, a similarity model test is conducted to simulate the dewatering process. In the laboratory experiment, by means of mini dewatering wells, the seepage process around wells is reproduced and the seepage effect on retaining wall deformation is studied. The test results indicate that the depression cone outside the foundation pit enlarges continuously during the dewatering. Meanwhile, cantilever-type wall deflection and spandrel-type surface settlement are observed. In addition, the dewatering leads to an apparent decrease of the pore water pressure in front of the wall, which further induces decrease of the lateral total pressure. In response to the stress change, the retaining wall moves towards the pit in a cantilever type to achieve a new equilibrium state, and further induces the surrounding ground deformation as a result of the ground loss behind the wall.

The soil-rock mixture (SRM) is composed of large-sized rocks, soils as filling component and pores. The strength and deformation characteristics of SRM are closely related to its fine contents (soil contents). The skeleton void ratio, referred to as the void ratio of skeleton particles, is proposed to study the strength and deformation characteristics of SRMs with different fine contents. Firstly, a series of compaction tests was performed to establish a packing model for SRM accounting for gradation effects, from which the expression of skeleton void ratio was derived. Triaxial drained tests were also conducted to verify the effectiveness of the proposed skeleton void ratio in predicting the strength and deformation characteristics of SRMs with different fine contents. It is found that the skeleton void ratio, compared with global void ratio, can better reflect the real density of soil-rock mixture by revealing the intergrain contact state of soil and rock particles. The mechanical behavior of soil-rock mixtures with different fine contents can be reasonably predicted by testing pure soils or rocks.

Rockburst has become an urgent safety problem in deep mining, and stress gradient plays a significant role in controlling rockburst. To explore the influence of stress gradients on the microscopic failure of surrounding rock, a pneumatic-hydraulic coupled rockburst simulation testing device was used to achieve six-sides loading in three-directions and the gradient loading in the top direction. When the gradient loading was applied at the top, the confining pressure was kept unchanged. Loading-unloading tests were carried out on rock similar material specimens by using rockburst physical models under different stress gradients. The analysis of microscopic morphology of failure surface was conducted using the scanning electron microscope (SEM). The results showed that failure phenomena and characteristics of rockburst were significantly different under varied paths of stress gradient. The greater the stress gradient is, the smaller the pores among the crystals is and the higher the density of the crystals is. The ratio of shear failure to splitting failure is different under different stress gradient paths. The higher the stress gradient is, the greater the ratio of shear failure is. The fractal dimension of detrital crystal contour increases with the increase of stress gradient.

Graded macadam fillings, the core filling of heavy haul railway subgrade bed is most affected by the train loading. Therefore, it is particularly important to study the dynamic behavior and accumulative plastic strain evolution characteristics of graded macadam filling under cyclic loadings. Firstly, graded macadam fillings with different fine particle contents were prepared, and a series of large-scale dynamic triaxial tests was conducted to explore the coupling influence mechanism of fine particle content, confining pressure, and dynamic stress amplitude on the specimen accumulative plastic strain under cyclic loadings. Additionally, based on the plastic stability theory, the dynamic behavior of specimens under different stress levels was determined, and the calculation model of critical dynamic stress in the plastic creep state was obtained considering the parameters of confining pressure and fine particle content. Finally, in combination with the experimental data, an accumulative plastic strain prediction model was established considering the stress level and fine particle content parameters for the dynamic behavior of plastic creep, and the physical meaning of each parameter was clarified. The research results can provide a reference for the health status assessment of existing heavy haul railway subgrades and the subgrade structure design considering the comprehensive control of strength and deformation.

In the study of early warning of backfill instability, the acoustic emission precursory characteristics have been recognized by many scholars. However, there are many forms of acoustic emission precursory characteristics, which have certain influence on the early warning of the backfill instability. Based on this, this paper attempts to establish a fixed form of early warning model of the backfill instability. First of all, based on the energy evolution characteristics and cusp catastrophe theory, an early warning model of backfill instability is constructed, and then the uniaxial compression acoustic emission verification test is carried out for backfill with different ash sand ratios. Experimental results show that the early warning state of backfill can be described by the interval composed of the catastrophe of dissipative energy and the catastrophe of releasable elastic strain energy, and the interval is defined as early warning interval. Moreover, the early warning intervals of backfill with different cement-sand ratios are unique, implying the model is extremely flexible and universal. The precursory characteristics of acoustic emission characteristic parameters with high recognition such as ringing counting rate are employed to verify the reasonableness of the early warning interval. It is found that the early warning interval calculated from the model is highly consistent with the time of the precursory characteristics of acoustic emission parameters, further proving the rationality and universality of this model and providing a new idea for the early warning of instability of backfill.

Based on the assumption of elastic support of soil nail, the expressions for calculating the real-time dynamic change of soil nail force and the seismic displacement of slope are derived by using the pseudo-static limit equilibrium method, considering the influence of real-time dynamic slip during earthquake. An improved method is proposed for calculating the seismic displacement of soil nailing slope under earthquake. The results of an example analysis show that the calculated time history curve of the slope horizontal displacement with and without considering the real time dynamic change of soil nail force are basically consistent. All results present a trend of step-wise increase, but the horizontal slope displacement calculated by the improved method is smaller, and the differences between results from two methods decrease gradually with the improvement of the overall stability of the slope. In the end, the rationality of the improved method is verified by comparing with the experimental data of shaking table test for a soil nailing slope.

This study focused on the influence of wall inclination and roughness on passive earth pressure for the retaining wall. Firstly, considering the friction between retaining wall and sliding wedge surface under passive state, the principal stress transfer law of a sliding soil wedge is described by the circular major principal stress trajectory. Subsequently, the method for determining the geometric parameters of the major principal stress trajectory is proposed. Then, the sliding soil wedge behind the retaining wall is divided into several circular thin-layer along the major principal stress trajectory. The new method of passive earth pressure is established by force analysis of the thin-layer element according to the static equilibrium condition. The method reflects the influence of wall-soil friction and wall inclination on the distribution of passive earth pressure. The problem that the complex stress of the element cannot be accurately considered by the linear thin-layer element method, commonly used in the current earth pressure analysis, can be avoided in the proposed method with more reasonable passive earth pressure calculations. Finally, comparison and analysis of distribution of passive earth pressure among the existing similar methods and the experimental results indicate the proposed method is reasonable and superior. Also, the influence of wall inclination and roughness on the distribution of passive earth pressure and the height of application of resultant force is discussed.

The physical and mechanical properties of aggregates are determined by their internal physical matrix-structuring, which cannot be directly demonstrated by traditional gradation curves. Also, there is a lack of optimal target function in designing of graded aggregates used in heavy-haul railway subgrade surface. This study established a grading curve model based on logarithmic probability regression equation and transformation of traditional gradation integral curve, and proposed a coefficient of matrix-structuring ‘R’. The mathematical expression of R was derived and the sensitivity of related parameters was analyzed. Based on the physical meaning of R, a practice engineering approach to optimize graded aggregates used in heavy-haul railway subgrade surface was proposed with the target of optimizing R. The feasibility of the proposed approach was verified by compaction test, large direct shear test and permeability test. The optimal value of R was determined by experimentation and optimization, between 21.17 and 22.08. Findings in this study provide reference for gradation optimization designing of graded aggregates used in heavy-haul railway subgrade surface.

In landslide stability analysis and design calculation, the residual strength value of slip zone soil is often selected, but many studies have found that the slip zone soil has self-healing phenomenon in the holding period, which is manifested as the increase of shear strength. For the red bed landslide dominated by creep, the application of recovered strength in the stability analysis of a reactivated landslide should be considered. The shear-hold-shear experiments are carried out on soil samples from a typical red bed landslide to determine the healing of shear zones under different vertical stresses and holding durations. The experimental data show that, the strength recovery occurs in the tests under different pressures, but the recovered strength will lose in very small shear displacement; the strength recovery value of the shear zone becomes larger and larger with the increase of holding time; self-healing of shear zones is more dependent on holding time than vertical stresses. The obtained friction coefficient values is fitted with the empirical formula of fault strength recovery, and the value of constant A under different vertical stresses can be obtained. The value of constant A can be applied to stability analysis of the reactivated landslide.

A self-made visual test device was used to carry out pullout model test of circular anchor plate, and the displacement and deformation fields of the soil around anchor plate were measured and analyzed in the limit state based on the digital photographic measurement technology. Under the test conditions, the ultimate bearing capacity increases nonlinearly with the increase of buried depth ratio, but the growth rate slows down gradually. The observed area surrounded by the soil sliding surface, the ground surface and the anchor plate present an inverted trumpet shape of “large bottom, small top, and long sliding surface”. The sliding surface can be approximated by two straight segments. The ultimate pullout mechanical model consists of an inverted trapezoidal cylinder with a small upper section and a large lower section and an equal-section cylinder. Based on the limit equilibrium conditions, an approach to calculating the ultimate bearing capacity of a shallow circular anchor plate in sand is developed. The calculated results of the four sets of test data by this method are closer to the measured values than by the other four methods, and the dispersion is smaller.

The depth to seismic bedrock and the nonlinear and hysteretic model of soil under cyclic loading have essential influences on the evaluation results of the nuclear island seismic site response. Using the one-dimensional (1D) equivalent linear wave propagation analysis (ELA) and nonlinear analysis (NLA) methods based on both the Matasovic and the Davidenkov-Chen-Zhao (DCZ) hysteretic models, three borehole profiles of 470 m depth with volcanic rock interlayer for the AP1000 nuclear plant located in the coastal deposits in China are selected to numerically simulate seismic site response. Five rock and soil layers with different shear wave velocities and depths are selected as the seismic bedrocks, the effects of input ground motion characteristics, the depth to seismic bedrock and the soil nonlinear and hysteretic model on the nonlinear site response characteristics of extremely deep deposit with volcanic hard rock interlayer are investigated. The results show that regardless of taking a shallow hard rock interlayer or a deep soil layer as the seismic bedrock, the 5%-damped surface spectral accelerations (SAs) at short periods calculated by the NLA method is greater than those calculated by the ELA method. However, the surface SAs at long periods calculated by the NLA and ELA methods are almost identical. Moreover, the curve shapes of surface SAs and peak accelerations along the soil depth calculated by the NLA method based on both the Matasovic and the DCZ models are basically consistent. Finally, from the surface peak ground acceleration and the cumulative absolute velocity calculated by the NLA method, it is suitable to select a shallow hard rock interlayer with the shear wave velocity of approximately 2 500 m/s as the seismic bedrock.

Based on the overall loading characteristics, this study was to propose an integrated deformation modulus for representing the integrated loading and deformation effect of the layered rock mass. The analysis of engineering cases was conducted to establish a theoretical model, which reflected the anisotropic characteristics of the integrated deformation modulus of the hard and soft layered rock mass. The theoretical solutions of integrated deformation modulus of hard and soft layered rock mass were separately deduced by using the plastic mechanics under the parallel, vertical and arbitrary directions of the stress to the bedding planes. The consistency of the theoretical solutions was also verified. We deduced the theoretical description of the integrated Poisson's ratio of the parallel direction of stress to bedding planes and the integrated shear modulus of the vertical direction of shear stress to bedding planes. The integrated deformation modulus was obtained by the geological model testing the hard and soft layered rock mass of the dip angles at 0o, 30o, 60o and 90o. The differences in the results from the laboratory test and the integrated deformation modulus were from 4.20 to 8.77%; therefore, the theoretical equation achieved great effects. This research studied the influence of engineering load direction on the deformation properties of layered rock mass by using theoretical analysis and laboratory tests, and improved the theory and technical methods for studying the mechanical parameters of the existing layered rock mass.

This paper is aiming to find a simple method for the settlement calculation of flexible pile composite foundation under embankment load. Firstly, the side frictional distribution of pile is simplified into a piecewise linear model based on the existing research results. Then, according to the relationship between the length of pile and the critical length of pile, combined with the coordination conditions of stress and compression deformation at the interface of pile-soil-cushion, settlement calculation formulas of flexible pile composite foundation reinforcement area are deduced by using the unit element method, and the settlement of underlying layer of composite foundation is calculated by layer summation method. Finally, the proposed approach is used to predict the settlement of an engineering example, and it is found that the predictions are in accordance with measurements, demonstrating that the approach is available in reflecting the working behavior of the flexible pile composite foundation under embankment load better. Further analysis shows that within the critical length of pile, the bearing capacity of soil between piles in composite foundation is maximized by the interaction of piles and soil. In addition, due to the drag effect of the negative frictional resistance, the axial force of pile at the position of the neutral plane reaches the maximum. Therefore, the concept of critical pile length and neutral plane should be highly valued and applied in engineering design.

The number of available site-specific test data is often sparse because of limited budgets and inherent restrictions at the project sites. It is difficult to evaluate accurate statistics of geotechnical parameters and slope reliability based on such limited test data. Bayesian analysis method can effectively reduce the estimation of the uncertainties of geotechnical parameters and improve the slope reliability by integrating the limited site-specific information. However, currently most Bayesian updating studies assume the prior probability distributions of geotechnical parameters as normal, lognormal and uniform distributions, and assume the likelihood function as multivariate normal distribution. The rationale behind this assumption needs to be verified. To this end, this paper summarizes commonly-used prior probability distribution and likelihood function models for Bayesian analysis in geotechnical engineering. An undrained clay slope is investigated as an example to explore the influences of the prior probability distribution and likelihood function on the inference of posterior probability distributions of geotechnical parameters and reliability updating of spatially varying slopes based on an adaptive Bayesian updating approach. The results indicate that the prior probability distribution has an important influence on the inference of posterior probability distributions and reliability updating of spatially varying slopes. The obtained posterior probability distributions of geotechnical parameters are less spread when the lognormal and extreme value I distributions are selected as the prior probability distribution. The obtained slope reliability results are conservative and risky, respectively, when the Beta and extreme value I distributions are chosen; while they are in the middle when the lognormal distribution is chosen. In contrast, the likelihood function has more significant effects. In comparison with the other types of likelihood function, the likelihood function constructed using joint multivariate normal distribution not only can reduce the estimation of the uncertainties of geotechnical parameters, but also can obtain more consistent results with the site-specific information. In addition, the autocorrelation of the measurement errors at different locations that used in constructing the likelihood function also has a certain effect on the posterior probability of slope failure.

The strength reduction method (SRM) has many advantages compared with the limit equilibrium method (LEM) in computing the safety factor of slopes, but the high computational cost, to some extent, limits the application of SRM in system reliability analyses of slopes. To effectively reduce the number of numerical analyses required for reliability analyses to alleviate the computation work when employing SRM, an efficient analysis method based on active-learning radial basis function (ARBF) surrogate model is introduced. This model uses the active-learning function to select trained samples near the limit state surface to update the surrogate model, which accelerates the convergence speed of the training process. With the linear kernel-based radial basis function, the optimization procedure of model parameters is simplified, by which a concise and stable surrogate model can be established. Moreover, an initial sampling strategy considering the characteristics of soil slopes is proposed to fully take advantage of active-learning process. Once a stable surrogate model is established, Monte Carlo simulation (MCS) is used to calculate the probability of system failure. As a comparison, two conventional reliability methods: active-learning Kriging (AK) model and the quadratic response surface method (QRMS), together with two typical soil slope cases, are tested to illustrate the computational efficiency and model stability of the introduced ARBF.

Red mudstone is a typical Jurassic sedimentary rock. It contains trace clay minerals, which is easy to soften in water, disintegrate when dehydrated, and has a certain swelling property. Red mudstone is an important factor that causes the continuous uplift of the subgrade for the Lan-Xin high-speed railway. Therefore, it is of great significance to redefine the expansibility of this kind of soil for the design and construction of ballastless track of high-speed railway. For this reason, the equivalent smectite content, cation exchange capacity, free expansion rate and liquid limit are selected as the indicators of mudstone expansion. The classification criteria for the expansion potential of the mudstone in the foundation are determined through a large number of field testing data. The weight of classification index combination is determined by using improved analytic hierarchy process (AHP), Gini coefficient method and intuitionistic fuzzy theory. The intuitionistic fuzzy comprehensive evaluation model of foundation mudstone swelling property is established based on the technique for order preference by similarity to ideal solution (TOPSIS method). The intuitionistic fuzzy comprehensive evaluation model quantifies mudstone swelling, and overcomes the shortcomings of different indicators of the same sample belonging to different levels. The applicability and accuracy of mudstone classification standard and intuitionistic fuzzy theory evaluation method to Lan-Xin high-speed railway are verified by laboratory expansion tests. The research results provide technical support for the risk assessment and control of long-term continuous uplift of red mudstone foundation for high-speed railway subgrade.

The mechanism of soil arching effect is the key technical problem for load transfer of pile supported embankment. However, the soil arching in pile supported embankment under high-speed railway load is not well investigated. Based on the code for design of high-speed railway, a three-dimensional finite element analysis model of pile supported reinforced embankment under high-speed railway load is established, and its correctness is verified by the existing research results. According to the numerical model, the dynamic response of subgrade under the high-speed railway load is analyzed, including the variation of vertical displacement with time at different depths of roadbed and embankment load, as well as the distribution of velocity and acceleration along the depth. The results show that the vertical displacement of the roadbed and the embankment surface changes with time in an inverted M shape periodically, while the embankment bottom changes in a V shape periodically. It is also found that the velocity and acceleration decrease by 80% along the depth of subgrade. Then, the influence of different factors including pile spacing, embankment height and the properties of the embankment fill on the stresses and settlements are comprehensively analyzed. Hence, the soil arching effect in piled embankment under high-speed railway loading can be investigated. It shows that the soil arching effect remains valid but weakened under the dynamic loading, which weakens the maximum under the peak load, while restores under the valley load. Also it is found that the influences of pile spacing and embankment height are obvious on soil arching effect under dynamic loading, while the effects of friction angle and dilatancy angle of embankment fill are relatively small.

Groundwater table might significantly fluctuate due to seasonal rainfall. In order to investigate the effect of the moving water table on the screening performance of multiple open trench barriers, a finite element model is developed to describe wave propagation in a layered ground, which is modeled as a dry layer resting on a saturated substratum. The effect of infiltrated water in trenches is considered in this model, and the vibration isolation efficiencies of multi-trench barriers with equal and unequal trench depth, multi-trench barriers with inclined trench wall and continuous undulating terrain barriers at different water levels are analyzed as comparable cases. Comparing with the corresponding single-phase elastic foundation, the numerical results show that a low permeability coefficient of the saturated substratum might have a significantly adverse effect on the vibration isolation efficiency for most of water tables. A triple trench barrier with a depth of 0.3LR (LR is Rayleigh wavelength) usually can achieve a satisfactory screening efficiency (i.e. 75% reduction), while the depth should be at least 0.6LR at the critical water table, where the worst isolation efficiency occurs. A multiple trench barrier with decremental depth can effectively reduce the adverse effect of the resonance. The larger sloping sides are, the better isolation effect of a barrier is for the shallow trenches, while it is not important for deep ones. Moreover, a rolling terrain landscape can be an environment-friendly isolation measure, which would achieve a great vibration isolation efficiency.

The sliding risk during spudcan reinstallation close to a footprint greatly threatens the structural integrity of jack-up units. In this study, a finite element model based on the coupled Eulerian Lagrangian method is proposed to simulate the process of spudcan penetration close to a footprint. Sensitivities of mesh density and loading velocity are evaluated, and the optimal parameters are chosen. With the proposed model, a parametric analysis is conducted. It is revealed that the generation of sliding loads including the horizontal force and bending moment is attributed to the asymmetry of the soil failure plane under the spudcan base, and the peak sliding loads increase with the footprint inclination, depth and diameter. The sliding loads reach the peak at a certain offset distance. The spudcan base inclination has a significant effect on the sliding loads. Reduction of spudcan base inclination results in a decrease of the sliding loads. The present work emphasizes the effects of geometric parameters of both the spudcan and the footprint on the sliding loads, which are of scientific significance to guarantee the safe operation of jack-up reinstallations close to existing footprints.

Tunnel settlement is an important index to evaluate the safety and stability of tunnel structure. Distributed optical fiber monitoring technology can obtain the strain distribution of the measured parts of the structure, but it cannot directly reflect the settlement of each part of the tunnel. In this paper, a tunnel settlement inversion model based on distributed optical fiber strain is proposed to link the optical fiber strain curve with the tunnel settlement curve. The feasibility of the model is verified by theoretical derivation, numerical simulation and laboratory tests. Through the distributed optical fiber monitoring project of the 07 bid of the new airport line of the new Beijing rail transit line, the strain curves of the tunnel vault are obtained under different working conditions during the period of dismantling temporary shoring of the tunnel. The settlement of the vault of the tunnel is calculated based on the optical fiber strain curve with the help of the tunnel settlement inversion model. The calculated results are in good agreement with the measured results of the construction monitoring center, and the error is within the acceptable range. The research results can provide theoretical and experimental bases for the application of distributed optical fiber sensing technology in tunnel settlement monitoring.

The high normal stress and constant normal stiffness are the general boundary constraint features of deep rock joints. Advanced rock joint shear servo test system with high normal load, large shear area, multi-shear mode and long shear distance is the premise for understanding the shearing deformation and failure of rock joints in deep stress condition. Thus, a new shear servo testing system, with large-scale, multi-functional and high-pressure, is invented. The system consists of normal and shear loading and unloading subsystems, servo control subsystems, data acquisition and software subsystems, and hydraulic oil source auxiliary subsystems. The functional parameters of the testing system include the maximum normal load of 1 500 kN, the maximum shear load of 2 000 kN. This testing system is available for the rock joint shearing test on the sample with standard sizes of 20 cm×10 cm×20 cm, 30 cm×20 cm×30 cm and 50 cm×30 cm×30 cm (length×width×height). The testing system can finish complex loading and unloading, constant normal loading (CNL), constant normal stiffness (CNS), fast/slow shearing, reciprocating shearing and other loading modes, assisting with shear observation window and acoustic emission positioning monitoring. Based on the test specimens of cement material and rock specimens, the experimental results show that this servo testing system can achieve high-frequency feedback control and data acquisition due to the excellent hardware structure and efficient software control, which can give out stable and reliable experimental data, support the stability study and engineering application analysis for deep rock engineering.

In the conventional visualization model test, the displacement and deformation in the two-dimensional observation window can be observed, but the out-of-plane displacement of the three-dimensional(3D) problem and the 3D deformation field cannot be obtained. Therefore, based on the transparent soil model test, a set of automatic tomographic scanning test device is independently developed in this study. The synchronous motion of the camera with the laser device is controlled by a high-precision electric linear platform to obtain a series of two-dimensional images. The improved image deformation measurement method is used for image post-processing. On this basis, the corresponding 3D reconstruction volume rendering program is coded to construct the 3D displacement field after deformation. In order to verify the feasibility of the visualization measurement system of spatial deformation, static pressure tests of square foundation and circular foundation in transparent soil are carried out. The test results show that the contour of the 3D vertical displacement and horizontal displacement after reconstruction are consistent with the theoretical prediction results and with those previously presented in the literature. The 3D vector displacement field can directly show the movement of soil mass at different positions, which eliminate that the 2D observation technique cannot reflect the out-of-plane displacement. This study not only further reveals the spatial deformation problem in static pressure test, but also provides a feasible method for realizing the observation of spatial deformation in the physical model test.