The shear stress relaxation of the anchor-soil interface is the key factor causing the prestress loss of anchor rod (cable). Firstly, a device for testing the shear stress relaxation of the anchor-soil interface was developed. Secondly, a constant interface shear displacement was applied in stages to the red clay anchored element sample, and the whole process of shear stress relaxation curve of anchor-soil interface was obtained, which can be transformed to the relaxation curve at each specific loading level by using coordinate translation method. Then, the theory of fractional calculus was introduced to improve the viscous pot element, and established the red clay-anchor solid interface shear fractional M||N (composed of Maxwell body and Newton body in parallel) relaxation model. The model parameters were yielded by regression analysis of relaxation test curves under partial shear displacements, and the relationship between the model parameters and the shear displacements was also obtained by fitting. Finally, the established fractional M||N relaxation model was applied to predict another part of the relaxation curve under shear displacement level. By comparing the integer-order M||N model, the Burgers model and the five-element model (H||M||M), the results indicate that the proposed fractional M||N relaxation model not only has the advantages of simple structure and fewer parameters, but also has higher fitting and prediction accuracy.

In this paper, the dissipative energy in the damage process was employed to solve the damage variable while the damage constitutive model was established. In this model, the Mohr-Coulomb criterion and the energy dissipation theory were introduced. Considering the hardening and softening characteristics of rock during loading, the non-associated plastic flow rule was applied to describe the plastic deformation of rock, and the damage variable was calculated by quoting the dissipation energy and damage energy dissipation rate in the damage process. Based on the conventional triaxial loading-unloading experiments, the energy consumption and damage evolution law of rock was analyzed. The expression of damage energy dissipation rate was established, and the parameters in the model were calibrated. Simulation was conducted by this model and the simulation results were compared with the experimental results to validate the model. In this process, the following conclusions were obtained: (1) in the elastic stage, the damage dissipation energy increases slowly with the axial strain, showing an upward concave curve, and the growth rate reaches the maximum near the peak-stress. In the residual stage, the relationship between damage dissipation energy and axial strain is linear; (2) based on elastic modulus associated damage definition, the experimental results show that there is a damage variable limit less than 1, and the damage variable limit gradually decreases with the increase of confining pressure; (3) the model in this paper can be used to investigate the strength, hardening, softening characteristics and strain law of rock under different confining pressures during the loading process. The numerical simulation results can describe the stress-strain relationship and damage evolution law of rock.

In order to make the properties of the coal briquette specimens(CBS) been closer to that of the raw coal specimens(RCS), and to improve the consistency between the relevant physical simulation test and the actual engineering, uniaxial compression mechanical properties, seepage characteristics and microstructure of the secondary carbonized hot-pressed CBS are tested and analyzed by changing the temperature conditions, and effects of temperature on the mechanical properties and microstructure of the briquette are also investigated. The results show that: (1) With the increase of carbonization temperature, an increase followed by a decrease is observed in the uniaxial compressive strength of secondary carbonized hot-pressed CBS. When the carbonization temperature is 300℃, its uniaxial compressive strength is close to that of RCS. (2) Under triaxial compression, the permeability of the hot-pressed CBS firstly decreases and then increases with the increase of axial compression, and the initial permeability shows an increasing trend with the increase of carbonization temperature. (3) The characteristic peak positions of the secondary carbonized hot-pressed CBS and RCS in the FT-IR organic functional group test are basically consistent. However, the corresponding characteristic peak strength is different, and the functional group response of the infrared spectrum of the secondary carbonized hot-pressed CBS at 300℃ and 450℃ is the closest to that of the RCS. (4) Compared with the RCS, the secondary carbonized hot-pressed CBS has a more uniform pore size distribution with a small proportion of micropore and small specific surface area. Moreover, as the carbonization temperature increases, the average pore size and specific surface area of the secondary hot-pressed CBS firstly decrease and then increase. Additionally, the pore size and specific surface area are relatively the smallest when the carbonization temperature is 300℃. The research results can provide references for the optimization of forming conditions of secondary carbonized hot-pressed CBS and the study of mechanical properties of secondary carbonized briquette.

Uniaxial compression experiments were carried out on prefabricated borehole samples. Acoustic emission (AE) and digital image correlation (DIC) monitoring technology were applied to explore the mechanical response characteristics of samples arranged in multiple rows and lines, and analyze the influence of the drillhole on the bursting liability, deformation and failure, accumulation and release of energy of coal samples. The results show that, destressing drillhole in coal seam could reduce the bursting liability, control the deformation and increase the deformation energy dissipation of samples. Compared with an intact sample, the strength of the samples with drillhole was significantly attenuated, and as the number of drilling rows increased, the pre-peak elastic modulus, peak stress, and the bursting energy index KE gradually decreased, and the bursting liability was reduced. Destressing drillhole could increase the activity intensity of AE events and reduce the proportion of high-energy events. The layout of the destressing drillhole caused change of the fracture mode of the samples. A strain localization area generates from the middle on the sample surface of the intact samples, and the final fracture occurs in this area as the weak surface. For the samples with single row and multiple lines of drillhole arrangement, cracks occur on the upper and lower sides of drillholes, forming a localization zone, which extend up and down to form macroscopic cracks. For the samples with double rows and multiple lines drillhole arrangement, cracks easily occur in the rock bridge between the same row of drillholes, and then the cracks in the rock bridge between the vertical drillholes further develope, and finally form the vertical and horizontal and oblique macroscopic cracks. Morevoer, the drillhole in sample could increase the vertical drilling direction (x-direction) deformation, reduce the parallel drilling direction (y-direction) deformation, enlarge the vertical direction (z-direction) deformation, and reduce the volume deformation. The drillholes could reduce the growth UV and peak value Umax of deformation energy density, and delayed the release rate URV of deformation energy at the moment of failure. When drillhole number is greater, the reduction amplitude of the peak deformation energy density Umax and the release rate URV are greater.

Due to its unique biogenesis, forming environment and deposition process, calcareous sand is featured with irregularity, brittleness, weak structure and low cohesion, and is considered substantially different from the common terrestrial sand deposits. Fine particles bonded with weak cohesion may be resolved by osmotic action and then migrate and reaccumulate, thus causing changes in porosity and permeability. This study has carried out filtration experiment and laser particle size analysis of exudate sediment under different initial conditions to analyze the principles of evolution, involving permeability coefficient and the characteristics of fine particle transporting during the filtration process in calcareous sand. The results show that the loss of fine particles tends to occur under the seepage condition, and that results in the local changes of soil structure and permeability. The factors including the grading, compactness and percolation hydraulic gradient play important roles in fine grain loss in the process of filtration. The results show that the higher soil coarse grain content is, the lower degree of compactness is, and the larger percolation hydraulic gradient is, which lead to the loss of fine particles easily and additionally, enlarging the size of losing particles as well as range of permeability variation. The main particle size range of fine grain loss during calcareous sand filtration is significantly affected by grading. The smaller the content of coarse grain in grading results in smaller particle size of grain loss, and vice versa.

Accurate acquisition of arrival time of microseismic signals is an important prerequisite for focal location, and the accurate acquisition of arrival time of P-wave and S-wave of microseismic signals has important theoretical significance. Based on the principles of time-frequency analysis and the arrival-time picking, the time-frequency analysis-downhill comparison method is proposed. According to the time-frequency analysis principle of this method, the position and rule of background noise, the frequency, amplitude and energy of microseismic signals before and after the initial arrival of P-wave and S-wave and smooth waveforms that facilitate the comparison of iterative averages can be obtained through spectrogram, power density spectrum and two successive FIR band-pass filters. By setting the mathematical expectation of the full wavelet amplitude as the threshold and iteratively comparing wavelet amplitudes of microseismic signals based on three relationships of power, arrival order and waveform overlap of P-wave and S-wave, the precise arrival time of P-wave and the arrival time of S-wave peak value are obtained. The advantages of this method over the improved STA/LTA method are compared by model tests and have been verified in an engineering example. The results show that: compared with the improved STA/LTA method, this proposed method can simultaneously pick up the precise arrival time of P-wave and the arrival time of S-wave peak value, while the latter can only pick up the accurate arrival time of P-wave. The average time difference and standard deviation of the former are 6.18 ‰ and 3.98 ‰ of the latter, respectively. Additionally, the average calculation time and standard deviation of the former are 43.99% and 10.54% of the latter, respectively. The failure ratio of the former is 0 while that of the latter is 15.63%.

Pile-net composite embankments are more and more widely used in high-speed railways construction, but the response mechanisms under the dynamic train load are still unclear. In this paper, a large-scale X-pile-net composite embankment model is established, and the dynamic response characteristics of a system consisting of subsoil, X-piles, reinforced cushion, the embankment, and track slab are investigated. The results show that as the train speed and axle load increase, the response amplitudes of the dynamic earth pressure, dynamic displacement, dynamic strain, and vibration speed increase as well. Due to the reflection of M-shaped wave at the interface between the pile tip and subsoil, the dynamic earth pressure exerted on the pile is larger than that on the pile. Compared to the embankment without piles and nets, the reduction effect of vibration on the piled embankment is remarkable. The increase in the dynamic strain of the geogrid above the pile is about 2 times that of the geogrid above the subsoil between of two piles. The transient dynamic strain in the middle and bottom of X-pile is larger. At the same location, the influence of loading frequency on the vibration velocity is much greater than that of loading amplitude. Compared with the surface of embankment, the increase in vibration velocity within the piled embankment is more affected by the loading frequency. The phenomenon of "resonance-like" has been detected in the embankment above the subsoil, which could be avoided by changing the rigidity of the embankment when building railways.

Coral sand is a type of soil with special engineering properties. It is of great significance to study the bearing capacity of coral sand for construction of islands and reefs in the South China Sea. The influence of density and gradation of coral sand, shape and size of load plate on the bearing capacity of coral sand foundation were quantitatively studied by self-made indoor model device of plate load, and bearing capacities of coral sand and quartz sand were compared. Test results show that, compared with quartz sand with the same density, coral sand has prominent flat features and sharp edges and corners, which leads to an increase of internal friction angle and further leads to an increase of its bearing capacity. Settlement under the same load is much smaller than that of the former, and size effect of foundation on bearing capacity is obviously greater than that of quartz sand. However, dependence coefficient of stress level of coral sand foundation soil is linearly related to its relative density, and internal friction angle is significantly affected by gradation. Relationship between bearing capacity coefficient of foundation Nγ and internal friction angle ? is established. At the same time, the bearing capacity of coral sand foundation increases with the increase of load plate size, and the bearing capacity of coral sand foundation under square foundation is obviously higher than that of circular foundation with the same area, and size effect is more obvious, which shows that the foundation type has practical significance on improving the bearing capacity in practical engineering. Based on the Meyerhof formula, a modified formula of foundation bearing capacity for coral sand is also proposed, which improves the accuracy of calculation results of bearing capacity of coral sand.

To investigate the macro-meso cumulative damage mechanism of the weak layer considering the impacts of various factors, the pre-peak cyclic shear tests and PFC2D meso numerical simulations were conducted. The results indicate that: (1) Three stages, i.e., initial compression-shear nonlinear deformation (elastic zone), nonlinear deformation of the cumulative damage due to the stress climb (elastic-plastic zone) and plastic deformation with constant stress (plastic zone), are observed in the weak layer cyclic shear deformation evolution curve and strength evolution curve. (2) The peak (residual) strength and cumulative shear (normal) deformation of the weak layer decreases and increases respectively as the cyclic shear times increase under the same conditions of moisture content, normal stress, shear rate, shear amplitude or relative thickness; conducted with the same cyclic shear times, the peak (residual) strength decreases, increases, decreases, decreases and increases with the increase of the mentioned factors in turn, while the variations of cumulative shear (normal) deformation present the opposite trends. (3) The evolution curve of the meso cumulative damage crack quantity includes four stages, i.e., a slight-steep, slow, steep and slight increase in the initial, preliminary, middle and later stages, respectively. Meanwhile, the weak layer energy evolution curve includes three stages, i.e., a steep, slow and slight increase in the preliminary, middle and later stages, respectively; besides, the meso-damage particles are distributed on both sides of the shear plane in an approximately “banded S-shape”. (4) The macro-meso cumulative damage failure modes of the weak layer can be summarized into three basic types, including the compacting-cracking failure (dilatancy effect), abrading-dislocating- gnawing failure (dilatancy-loosening-shrinkage effect) and penetrating-sliding failure (shrinkage effect).

The creep slippage of active fault leads to shearing of rock mass along the tunnel axis, causing axis bending and even destruction of rock mass. The nonlinear distribution of creep slippage displacement in rock mass plays an important role in structural design and operation safety of tunnels. In deep buried area, the three-dimensional in-situ stress and the structure of fault strips are the key factors to be considered, which are evidently different from geological conditions in shallow buried tunnel or subway project. However, the existing physical simulation tests are mostly used to study faults in shallow buried tunnels, subways and other projects, and are not suitable for the simulation of deep tunnel conditions. In this paper, a new experimental setup for physical modelling of deep buried tunnel crossing active fault is developed and utilized to simulate fault creep slippage under three-dimensional in-situ stress. Based on the Fenghuangshan tunnel that crosses active fault, the axis displacement mode along the tunnel under different slippages is obtained through physical model test. The results show that the displacement mode along the tunnel axis is S-shaped. The shear deformation is continuously transmitted from slippage plane to crushed zone under small slippage, while the slippage occurs between slip plane and crushed zone under large slippage. The deformation curve within the crushed zone is ‘slope line’ shape, and the transmission width within the zone is around 20 m. This result could provide important knowledge for the structural design of fault crossing tunnels.

To study the environmental vibrations induced by train loads, an analytical model for a track coupled with a layered transversely isotropic (TI) ground is developed. The model can consider the alternate distribution of TI elastic and poroelastic layers in the ground to describe soils and rocks under different moisture conditions compared with existing models comprising only one type of medium. Based on the analytical model, the governing equations of TI media are solved firstly using Fourier transform and a potential function method. Then the exact stiffness matrix method is adapted to derive solutions to the layered ground with different media. Finally, the dynamic response of the coupled system is obtained by using the governing equations of the track and inverse integral transformation. The influences of groundwater existence and transverse isotropy on the vibration of track and ground are investigated. It is found that the influence of the groundwater existence in the TI poroelastic layer on the track force amplification factor is significant at load frequency lower than 200 Hz. The ground surface vibration attenuates faster with the distance from the track center for a larger ratio of the horizontal elastic modulus to the vertical one. The maximum vertical stress magnitude occurs within 1 m from the ground surface. The critical speed of the displacement and stress increases with the increasing ratio of the horizontal elastic modulus to the vertical one.

The influence of temperature variation on soils’ strength and deformation cannot be neglected in geotechnical engineering, such as shallow geothermal energy extraction, nuclear waste disposal, and the construction of geothermal structures. To comprehensively describe the thermomechanical behavior of soils, a thermo-elasto-plastic model of saturated clay that incorporates the temperature effect is established based on the disturbed state concept. By considering the thermal dependence of the volumetric strains and critical state, a disturbance function is introduced to reflect the influence of overconsolidation ratio (OCR) on the strength, dilatancy and deformation of saturated clay. The disturbance function is incorporated into the dilatancy stress ratio, potential failure stress ratio, and plastic modulus. Finally, the proposed model is validated through the isotropic heating-cooling tests, temperature-controlled drained triaxial compression tests, and temperature-controlled undrained triaxial compression tests. The proposed model can properly reflect the thermal-hardening and thermal-softening behavior of the saturated clay. The strain hardening and volumetric contraction of normally consolidated clays, as well as the strain softening and volumetric expansion of overconsolidated clays under the drained condition are well captured. Meanwhile, the proposed model can describe the strength and stress paths evolution of saturated clay under the undrained condition.

In order to carry out the research on the focal mechanism solution of rock mass microseisms, the analysis is based on the moment tensor theory. In view of the limitations that the Ohtsu’s decomposition method and the rock mass fracture type criterion are only suitable for the rock mass under tension conditions, the moment tensor decomposition model of the rock mass under compression is adopted. By discussing the positive and negative of the compensated linear vector dipole (CLVD) component, the component calculation expression is improved and the isotropic (ISO) component is introduced to modify the rock fracture type criterion; meanwhile, the CLVD-ISO diamond source type map is adopted to illustrate the characteristics of various rock mass fracture types. Besides, the tension source model is adopted for characterizing the fracture surface occurrence with the deficiencies of the double-couple (DC) component (MDC) taken into considered. On this basis, the analyses of focal, including the source mechanism, the mechanical mechanism and the spatial distribution characteristics of the source fracture surface are carried out combined with a typical engineering case of Xianglushan Tungsten Mine. Based on the modified criterion, the results indicate that the main types of rock mass fracture in this case are tension fracture and compression fracture. Furthermore, the special distribution of source fracture surface parameters are obtained with the tension source model adopted. The analysis results are basically consistent with that in actual situations, which also verify the application of the improved model in the focal mechanism solution analysis of engineering microseisms based on the moment tensor theory.

In this paper, based on the axisymmetric consolidation theory of unsaturated soil and equal-strain assumption, an analytical solution using the homogenization of boundary conditions and eigenfunction method is proposed to three-dimensional consolidation of unsaturated soil enhanced by vertical drains under instantaneous loading, in which the continuous permeable boundary conditions are properly introduced. Then, the proposed solution is verified by the special cases of double drainage boundary conditions. Finally, the solution is analyzed using examples and the results show that the proposed solution can be used to simulate the arbitrary distribution of permeability of the top and bottom boundary by setting reasonable interface parameters, which makes up for the problem that the permeability of the top and bottom boundary is between pervious and impervious condition or follows an asymmetric distribution. In addition, with a proper ratio of influence radius to drainage well radius and appropriate depth of vertical drain, the influence of vertical flows on the dissipation of excess pore pressures is small when the ratio of radial to vertical permeability coefficient is greater than two. Last but not the least, the above influence of excess pore pressures is more obvious with the enhancement of the permeability of the top and bottom boundary considering the vertical flows.

There are many landslide deposits in the reservoir and bank areas of hydropower projects in southwest China. These deposits are easy to deform and fail along the existing sliding zone under hydrodynamic conditions, such as rainfall and reservoir water fluctuation. The slip soil in Dahua landslide deposits which are located at the Dahuaqiao Hydropower Plant in the Lancang river basin of southwest China, was studied as an example. The experimental study was carried out to explore the soil-water characteristic curve (SWCC) of slip soil. The permeability characteristics and the evolution in the unsaturated seepage process were analyzed, and the saturated permeability characteristics under different confining pressures and seepage pressures were studied. The results indicated that the VG model could be used to describe the SWCC and the variation of relative permeability coefficient of Dahua slip soil. Through the saturated permeability test, it is found that under the same other conditions, the larger the confining pressure is, the weaker the saturated permeability of the slip soil is; while the larger the seepage pressure is, the stronger the saturated permeability is. Furthermore, the saturated permeability characteristics of the slip soil manifested a strong non-Darcy flow behavior, and the relationship between permeability velocity and hydraulic gradient satisfied the Forchheimer binomial model. When the confining pressure was low, the linear term coefficient of velocity had a more significant effect on the permeability, whereas the quadratic term coefficient of velocity gradually dominated in the seepage process with the increase of confining pressure.

The traditional rock-breaking mode of mechanical-rock interaction can no meet the requirement of large improvement of tunneling efficiency of TBM. Innovative rock-breaking technology and its rock-breaking mechanism have gradually been paid more and more attention. On the premise of not changing the main structure of TBM, the penetration test using TBM constant cross-section hob indenter has been carried out on rock samples with three different lithology under lateral constraint conditions. The influence of pre-cutting groove on rock-breaking mode of mechanical cutter are studied. The results show that: (1) Pre-cutting groove can reduce the normal load of indenter when the rock sample is broken, and the normal load of the rock sample with pre-cutting groove is reduced by 44.13%-53.05% compared with that without groove. The lower the uniaxial compressive strength of the rock is, the larger the reduction ratio of normal load will be. (2) There is a critical value for the influence of pre-cutting groove depth on the normal load when the rock sample is broken. Beyond this critical value, the influence of pre-cutting groove depth on the failure behavior of the rock sample is weakened. Based on the above investigations, a new combined rock-breaking mode of pre-cutting groove and mechanical cutter is proposed, and an innovative rock breaking technology that can realize pre-cutting groove is discussed. The combined rock-breaking mode can break through the bottleneck of rock-breaking efficiency and is of great significance for TBM equipment upgrading and major engineering project construction.

To investigate the longitudinal initiation and diffusion mechanism of rock fracturing and grouting, the movement law of the rheological property of slurry and the form of the crack propagation are analyzed considering the mechanical properties of the injected rock mass and ground stress. In addition, the longitudinal fracturing diffusion model considering the rheological property of slurry is established, and the initial pressure of longitudinal fracturing and the expansion conditions of fracturing channel are given. Taking the fracture geometry and the rheological property of the slurry into account, the slurry diffusion equation is derived and verified by experiments. Studies have shown that, in addition to the factors such as grouting pressure and grouting rate, the diffusion range is also controlled by the height of the grouting section, the strength of the injected rock body, and the rheological property of the slurry during longitudinal fracture grouting. These influencing factors are all negatively correlated with the fracturing diffusion radius and positively correlated with the grouting pressure. The rock mass with high strength and the liquid with great viscosity can lead to high resistance encountered by the fracturing grouting, which can further result in difficult crack propagation. The research results can provide a theoretical reference for fracture grouting designs of the bedrock in the future.

The variations of the diameter and mass attenuation of rock samples with the number of freezing-thawing cycles are obtained, and it is pointed out that 80 freezing-thawing cycles are the inflection points of the variation lines of diameter and mass of quartz sandstone. A technical method for the accurate CT identification of progressive damage is proposed, and the main damage areas of the sample are defined and subdivided. Moreover, the freezing-thawing damage model of progressive damage at stages before and after spalling is also established. Linear relationships between CT value, elastic modulus and porosity are established, and it is concluded that: (1) After 40 freezing-thawing cycles, the elastic modulus of the outermost ring layer is 0, and the CT value is not 0 at this time. Additionally, the ring layer doesn’t peel off. (2) After 80 freezing-thawing cycles, the CT value of the outermost layer is 0. Meanwhile, the porosity of the layer is the largest and the layer is peeling off. (3) The deterioration of the inner layer of the sample at the second stage is significantly greater than that at the first stage. According to this finding, the bundle hoop effect of the outer layer and the accelerated degradation effect of the inner layer are proposed, which can also be explained based on the mechanical mechanism. On the basis of images of changes in porosity, loss rate of elastic modulus and mesopore after several freezing-thawing cycles, the development and evolution of progressive damage are further quantitatively illustrated. Based on the variation law of elastic modulus and porosity with the number of freezing-thawing cycles, respectively, the degradation factor “ ” of the freezing-thawing elastic modulus is defined, and a formula for predicting the elastic modulus degradation of progressive damage is also established based on the zone division of progressive damage. Finally, the feasibility of the above method is verified by comparing the calculated values with the measured values.

The initiation and propagation of cracks will greatly affect the strength, deformation and permeability of soil, and then lead to various engineering disasters. In order to further explore the crack initiation and propagation mechanism of soil, the local water contents in three stages were measured. Besides, the lateral shrinkage characteristics of soil were also tested with the change of water content. The mechanical mechanism of the cracking process was analyzed, and the quantitative calculation and discriminant formulas for the whole cracking process of shallow soil were established. The results show that the vertical water content distribution increases linearly with the increase of soil depth during the first two cracking stages, and the cumulative horizontal shrinkage increases with the decrease of water content. Based on the surface water content and depth of shallow soil, the mathematical expressions of tensile strength and tensile stress for shallow soil can be deduced, and then the three typical cracking stages of shallow soil can be analyzed. At the early stage of cracking, the generation of new cracks leads to the decrease of tensile stress on the soil surface. The basic indicators such as total crack length, and the average width and degree of cracks, are related to tensile stress. The correlations between tensile stress and crack indicators could explain and describe the complex change process clearly in the initial stage of cracking. Moreover, combined with the initial defects of soil and the stress concentration at the crack edge, the cracking process was further analyzed and discussed.

The hollow cone-shaped foundation is an innovative foundation for onshore wind turbines. Model tests were carried out to investigate the influences of foundation sizes and loading eccentricity on the bearing behavior and earth pressure distribution along the foundation embedded depth under monotonic horizontal loading. Results show that the horizontal bearing capacity of the cone-shaped foundation increases with the increase in the diameter of the foundation and the decrease in the loading eccentricity. When the normalized loading eccentricity, (H is the loading eccentricity and is the diameter of the foundation top plate), increases from 0.5 to 1.0, the bearing capacity decreases by approximately 43%. When the ratio of the base plate diameter to the top plate diameter of the cone-shaped foundation is higher than 0.28, the bearing capacity of the cone-shaped foundation is larger than that of the regular circular gravity-based foundation under the same top plate diameter and foundation height. During horizontal loading, the cone-shaped foundation rotates about the rotation center. The rotation center moves downwards and forwards with the increase in horizontal loading, and then tends to be a stable position. The sand in front of the foundation is in the passive earth pressure zone. The size of the passive earth pressure zone decreases with the increase in the horizontal load. A method of predicting the effective area between the foundation and the sand is proposed in terms of the force equilibrium. The effective area predicted using the proposed method agrees well with the model test results. The error between the calculated result and the test result is 4.5%.

Based on the summarized characteristics of vein rockburst in the Uzbekistan Kamchik tunnel, the paper analyzed the formation mechanism of vein rockburst, established the mechanical model of the most dangerous vein rockburst in side wall of Kamchik tunnel and proposed corresponding controlling technology for rockburst. The research shows that the characteristics and hazards of vein rockburst are closely related to the location and thickness of the vein. The formation mechanism of this rockburst type is inconsistent with rockburst under single lithology. Vein rockburst occurred in vault of Kamchik tunnel results from the maximum tangential stress on vault after tunnel excavation. Exposed vein rockburst of side wall is caused by excavation unloading and vertical stress concentration in side wall, and the mechanical model can be simplified as the crushing instability when the thin vein plate is cut by unloading crack after the vertical stress concentration. Hidden vein rockburst behind side wall is mainly due to the horizontal extrusion of the vein behind granite and the vertical stress concentration of side wall after tunnel excavation. The mechanical model can be simplified as the bending and breaking of the free rock plate (pillar) of the side wall under the combined action of vertical stress and horizontal compression of the vein. The horizontal extrusion of vein towards granite rock plate (pillar) of the side wall is a major contributor to hidden vein rockburst behind side wall. It mainly comes from the "Wedge extrusion" caused by intrusion of vein and the horizontal extrusion from the horizontal differential deformation between vein and granite that are suppressed by granite. Hence, timely application of anchors on the side wall is an efficient way to prevent vein rockburst of side wall.

Risk assessment of tunnel boring machine (TBM) construction is affected by many uncertain factors. The traditional fuzzy analytic hierarchy process (FAHP) tends to weaken the influence of some prominent risk factors due to the use of linear operators for calculating risk levels, reducing the accuracy of the final assessment results. This paper introduced a nonlinear operator into the comprehensive calculation of traditional FAHP, and established a new risk assessment model for TBM construction based on the nonlinear FAHP. Based on the work breakdown structure method (WBS) and the risk breakdown structure method (RBS), a risk assessment index system for TBM construction was also established. To calculate the weight of risk factors in the risk assessment index system and to construct the fuzzy relation matrix, analytic hierarchy process (AHP) and the membership vector obtained from the expert evaluation method were adopted. Through introducing the nonlinear operator, the weight of risk factors and fuzzy relation matrix were analyzed, and on this basis the final risk level for TBM construction was obtained based on the principle of the maximum membership degree. The proposed model was successfully applied to the risk assessment of a TBM crossing the F2-2 secondary fault in Yangtaishan Tunnel of Shenzhen metro and the risk level of TBM construction crossing the fault section was determined to be level 4, which was a high risk. Finally, to further verify the reliability of the proposed model, the difference between the new risk assessment model and the traditional FAHP evaluation method was discussed based on the Yangtaishan Tunnel project.

In recent years, accidents caused by horizontal frost heave frequently occur in foundation pit projects over winter in seasonally frozen soil areas, but there are few researches on anti-frost heave measures. In this paper, the field monitoring of foundation pits over winter of pile-anchor supporting structures in Changping District of Beijing is carried out, and the evolution law of frost heave characteristics such as soil moisture migration, stress state of supporting structure and horizontal displacement of slope protection pile is analyzed. A hydro-thermal coupling model is established, and the model is verified by comparing the results with the monitoring data. Taking the temperature field distribution, horizontal displacement of slope protection pile and horizontal frost heaving force of supporting structure as indexes, using numerical calculation results, the suppression effects of insulation layer and replacement of non-frost heaving soil and setting parameters on horizontal frost heaving are compared, and the effective anti-frost heaving measures are put forward. Studies have shown that the freezing of foundation pit soil is caused by the combined action of vertical and lateral water migration; the inhibition effect of laying an insulation layer on frost heaving is significantly better than replacing non-frost heaving soil. Laying an insulation layer is recommended to be used in projects since it is more economical, feasible and easier to operate. The research results can provide theoretical support for the design and construction of supporting structures in cold areas in the future.

The mechanism of surrounding buildings on the seismic response of subway stations was investigated based on the dynamic equilibrium characteristics of the building-soil-subway station model and a simplified method for the seismic design of subway stations considering the effects of surrounding buildings was proposed in this paper. A near-field model including a subway station and a surface building was established firstly. Comparing the dynamic characteristics of the near-field model to the model without surface building, we found that the seismic forces of surface building induced in an earthquake would be passed to subway station through the foundation and field. Since the main seismic forces of surface building were inertia forces which could be calculated using the response spectrum method, a simplified method was derived. Owing to acquiring the dynamic response of subway stations via static modeling and calculating, the method proposed herein consumes less analysis time and cost. Furthermore, a series of numerical simulation experiments was conducted to verify the simplified method and further evaluate its computational accuracy. The results of those tests revealed that: compared to the results of dynamic time history, errors in internal forces and deformations of the simplified method are less than 7% and 5%, respectively. Therefore, the simplified method has a high accuracy in engineering design.

Based on the original monitoring data of Nanoujiang VII grade CFRD, a joint inversion method of transient-rheological parameters for rockfill dam based on the incremental analysis was proposed. The parameters of the incremental rheological model and E-B model of rockfill were inversed using the immune genetic algorithm. The reliability of the measurement results and the accuracy of the inversion analysis of hydraulic overflow settlement gauge were studied. The results show that: (1) The laboratory test parameters of the rockfill materials obtained according to the current norms are much higher than the parameters of the practical field filling body, and the calculated settlement is 28% less than the measured value of the dam. (2) Due to the fact that the embedding time lags behind the actual filling process of the dam and the existence of the soil arching effect, the measured settlement from the hydraulic overflow settlement gauge is 45% less than the actual settlement of the dam. The measured deformation cannot be directly used for the inversion analysis. (3) According to the embedded condition of the field monitoring instruments, the function relation between the leakage measurement and the ratio of inside soil pressure to outside soil pressure of the trench is established, which can be used to correct the measured value of the hydraulic overflow settlement gauge. (4) The incremental inversion method in different periods can avoid the miss and less measurement value in the measurement process of the hydraulic overflow settlement gauge. The calculated value is in good agreement with the actual deformation, and therefore it is more suitable for the back analysis of mechanical parameters of earth-rockfill dams.

In tunnel design and construction, the stability evaluation of tunnel roof wedge usually adopts traditional deterministic analysis methods, which cannot appropriately reflect the spatial variability of rock mass. Based on limit equilibrium method, an efficient approach for evaluating the safety factor integral expression of tunnel roof wedge is presented in this study. This approach considers the influence of spatial variability of rock mass joint friction angle and is validated by universal distinct element code (UDEC). Based on random field method and Monte Carlo simulation (MCS), a generated random field is substituted into the established safety factor integral expression to calculate the safety factor of the tunnel wedge, in which the spatial variability of rock mass joint friction angle is well considered. The failure probability of roof wedge is calculated with consideration of geological and geometry parameters uncertainties. The results indicate that the spatial variability of rock mass joint friction angle has a significant influence on the failure probability of tunnel roof wedge. Ignoring the spatial variability of rock mass mechanical parameters will cause an overestimated failure probability of tunnel roof wedge.

In this paper, a three-dimensional numerical simulation model is established based on smooth particle hydrodynamics (SPH) method. In this model, the dynamic behavior of debris flow is described by using the Bingham fluid model, and the bridge pier is regarded as the terrain condition. The repulsive force at the boundary is introduced to improve the boundary condition. Based on flume experiments, the accumulation processes of debris flow impacting the bridge pier with various viscosities and characteristics of the impact force-time curves are analyzed. The physical models are established, and the simulation of three-dimensional dynamic evolution processes of debris flow impacting the bridge pier with various rheological parameters and weights are realized. Moreover, the simulation results of the accumulation processes of debris flow with various rheological parameters and the impact force-time curves are analyzed. It is found that there are differences between the simulation results and the experimental results of the dynamic evolution processes of low-viscous debris flow impacting the bridge pier. From the view of fluid mechanics, the primary reason lies in the ignorance of the energy dissipation owing to lack of a description of Reynolds stresses caused by turbulence. Besides, the bridge pier safeguard procedures under the impact of debris flow with various viscosities are discussed. This work provides a theoretical support for further optimization of the three-dimensional numerical calculation model of debris flow impacting the bridge pier.