In order to realize the visualization of unsaturated preferential flow migration of soil, a column device was designed to carry out unsaturated seepage tests. The transparent soil and digital image processing technology were used to establish the relationship between the normalized pixel intensity and the saturation of transparent soil. On this basis, the effects of the connectivity of the preferential flow path and the rotation angle of the adjacent preferential flow path on the preferential flow migration in unsaturated soils were studied by conducting laboratory model tests. The results showed that it was feasible to characterize the saturation of unsaturated transparent soils based on the intensity of image gray pixels. The profile of fully connected preferential flow (O-O type) and upper connected preferential flow (O-C type) presented T-shape. The saturation of the central axis profile was obviously different from that of the central edge profile. In the lower connected preferential flow path (C-O type), the soil oil pressure and matrix potential could not make the fluid enter the preferential flow path to form the preferential flow, in which the change of infiltration was consistent with the uniform flow. The stable infiltration rate and the wetting front moving velocity of O-C preferential flow were 1.5 times and 1.4 times of those of the C-O type, respectively. A new preferential flow was formed in the area between adjacent O-C preferential flows. The soil in that area reached higher saturation and the growth rate of saturation decreased with the increase of rotation angle. When the preferential flow rotation angle was 90?, 60? and 30?, the stable infiltration rate was respectively 1.5 times, 1.3 times and 1.2 times that of the uniform flow. As the fluid was affected by gravity, the preferential flow with a small rotation angle only infiltrated horizontally along one side of the path. However, the moving velocity of the wetting front was 1.3 times, 1.4 times, and 1.5 times that of uniform flow, respectively. The interaction between adjacent preferential flows was weakened, so it was difficult to form the new preferential flow.

Under desiccation conditions, the argillaceous cement of red bed mudstone will crack due to the change of water content, and the cracks will develop further and finally lead to the disintegration of red mudstone. At present, the research on the disintegration mechanism of red mudstone is mostly qualitative description, lack of quantitative analysis method. Therefore, the quantitative study of the occurrence and propagation of the red mudstone argillaceous cement cracking is of great significance to the further theoretical study of the red mudstone disintegration. Based on linear elastic fracture mechanics and unsaturated soil mechanics, a formula that considering water content change was developed to calculate crack depth and spacing of argillaceous cement in red mudstone, and the sensitivity of the formula parameters was analyzed. CT test data were used to calibrate the PFC2D numerical model, and based on the numerical test results of desiccation cracking, the formulas of fracture depth and spacing were compared and verified. The proposed formula can well predict the crack depth and spacing of the red layer argillaceous cement, and the crack depth increases rapidly at first and then slowly with the decrease of water content. The research results are helpful to deepen the quantitative theoretical analysis of red mudstone disintegration and provide reference for predicting the degree of red mudstone cracking in engineering.

In view of the imperfection of the calculation method of horizontal frost heaving force in the design of L-shaped retaining wall in permafrost area, based on the Lifking foundation model and the cooperative deformation principle between retaining wall and soil, a simplified calculation model of horizontal frost heave effect of L-shaped retaining wall with or without replacement soil behind the wall is established, and the proposed calculation model is solved by superposition principle and finite difference method. Furthermore, the water-thermal-mechanical coupling analysis software is developed by MATLAB. Combined with an engineering example, the horizontal frost heaving force obtained by using the proposed calculation method is compared with the field measured value, the corrected earth pressure value, the code empirical value and the simulation value of the coupling software. The results show that: (1) the horizontal frost heaving force obtained by the proposed calculation method is in good agreement with the field measured value and numerical simulation value, while the corrected earth pressure value and the code empirical value underestimate the effect of horizontal frost heaving force on the retaining wall; (2) compared with the code empirical value and field measured value, the horizontal frost heaving force obtained by the proposed calculation method presents two distribution modes of parabola and trapezoid along the wall height, which is more general; (3) the multifield coupling analysis shows that the frost heaving force trend obtained by the proposed calculation method is similar to the trend obtained by the coupling method, which indicates the feasibility of the calculation method and can provide some theoretical support and guidance for the design of L-shaped retaining wall in permafrost area.

Aiming at the dredger fill with high clay content, a series of vacuum preloading model tests and microscopic tests were carried out in this study, to discuss the reinforcement effect and mechanism of the chemical modification combined with vacuum preloading method. The results show that the liquid limit and plasticity index of the dredger fill were both reduced notably, while the coefficient of permeability of the dredger fill was significantly increased; in addition, the microscopic tests results show that a series of complex chemical reactions happened between modified admixture and soil particles due to chemical modification, and it can be observed that a large amount of insoluble substance was attached to the surface of the dredger fill particles due to the chemical modification, which contributed to a typical aggregate structure and increasing the pore diameter, and leading to a significant improvement in the permeability of the dredger fill. Compared with traditional vacuum preloading method, the chemical modification combined with vacuum preloading method has greatly improved the reinforcement effect of the dredger fill. The maximum increases in vacuum preloading drainage and vane shear strength of the dredger fill reinforced were 17.6% and 69.0%, and the surface settlement increased significantly. This research provides a theoretical basis for improving the technical development of vacuum preloading method.

To study the characteristics of sandstone crack propagation under hydraulic coupling, sandstone laboratory tests were conducted under different seepage pressures and confining pressures. Under the same effective confining pressure, it is shown that the rock brittleness index becomes higher as the seepage pressure increases, while the crack initiation stress, the crack damage stress, and the peak stress decrease gradually. The initial volumetric strain of the crack decreases, and the volumetric strain of crack propagation decreases firstly and then increases afterward. The growth rate of the crack axial strain and the crack circumferential strain are both increasing that corresponding to the damage stress and the peak stress, however, no obvious relation is observed between the growth rate of the crack volume strain and the seepage pressure. Under the same seepage pressure, the initiation stress, damage stress, and peak stress gradually increase as the effective confining pressure increases. In addition, the growth rates of the crack axial strain, circumferential strain and volumetric strain increase gradually during deformation that corresponds to the crack initiation stress, damage stress and peak stress, respectively. When comparing the different growth rates of crack strain for a tested sandstone specimen, it is found that the strain growth rates have the following order: the crack axial strain > the crack circumferential strain > the crack volume strain.

In existing norms, the method for basal heave stability analysis of excavations is mainly the circular sliding method. This method bases on the limit equilibrium theory and has no rigorous theoretical basis. The safety factors derived by the circular sliding method are generally overestimated, and the derived safety factors are highly deviant when the wall embedment depth ratios are relatively small. The limit analysis method has a rigorous theoretical basis, based on which some failure mechanisms have already been proposed. However, there is a lack of research on the applicability of these mechanisms. In this study, the theoretical framework of the upper bound analysis for basal heave stability analysis is introduced, and the concept of mechanism optimization as well as the combined mechanism of rigid blocks and continuous velocity field are discussed comprehensively. The upper bound mechanisms are compared with the elastoplastic finite element method in uniform clay ground and the circular sliding method in non-uniform clay ground respectively. The applicable conditions of these mechanisms are concluded. The results show that the stiffness of the wall should be treated as infinity when the stiffness is large and the embedded depth ratio is relatively small, while the influence of the stiffness should be considered when the stiffness is small and the embedded depth ratio is relatively large. The proposed circular upper bound mechanism is verified by a field case study.

Huge hazards are often caused by earthquake-induced rock slope failure. The study of dynamic response characteristics and failure mechanism of the rock slope in certain geological condition is an important issue in geotechnical engineering. Taking the Shuiqiuchi rock slope failure as an object of study, a shaking table test was carried out to study the dynamic response and failure mechanism of rock slope controlled by faults. The testing results show that when the dip angle of the fault is greater than a specific critical angle, part of the reflected and transmitted waves at the discontinuous interface change into sliding waves, resulting in a sudden change in the acceleration response at the fault. The peak acceleration amplification factor inside of the model slope presents a significant three-stage trend. Peak horizontal acceleration amplification factor increases obviously with the increase of elevation, while peak vertical acceleration amplification factor increases slightly with elevation. The natural frequency curve of the model slope can be divided into three stages with a downward trend, which indicates that the dynamic characteristics of the model have changed. By comparing the shaking table test with the Shuiqiuchi rock slope failure prototype, it is found that the main failure mode of the rock slope with fault structure is that the top of the slope first shows vertical tension cracks under the seismic load, followed by cracking damage of the broken rock body on the upper plate of the fault, and finally shear sliding occurs along the fault surface. This research will set example for the early risk warning of granite rock slope failure, and provide the basic data and scientific support for the development of Qinling Mountain geological heritages.

The hollow cylinder torsional testing system (RHCA) was used to conduct true triaxial test on gray sandstone. Controlled conditional compression tests (?2??3), constant ?3 and variable ?2 conditional compression tests were carried out respectively. ?2 is the intermediate principal stress, ?3 is the maximum principal stress. Strength and failure characteristics were analyzed in detail, and intermediate principal stress effects, minimum principal stress effects, stress Lord angle effect and applicability of strength criterion were further analyzed. The results indicate that rock hollow cylindrical apparatus can realize the simulation of true triaxial stress path and the end friction can be avoided. The pressure difference between the inner and outer confining pressure has a great influence on the strength of the rock, especially under high confining pressure, a large pressure difference makes the strength of the rock weaken rapidly, resulting in severe damage. The intermediate principal stress has a significant effect on the strength of the rock and has an interval effect, and the minimum principal stress has a strengthening effect on the strength of the rock. This feature has an important guiding significance for the efficient and timely support of the rock mass in actual engineering excavation. Further, according to the obtained test results, the strength criteria used to describe the mechanical properties of the rock at this stage were analyzed. It is considered that the calculated rock strength obtained by using the exponent criteria can better reflect the stress state of rock and has a relatively good applicability. It can be used to evaluate the strength of rock in practical engineering.

Macro-meso parameter calibration of the contact model is the key to successful use of the discrete element method. Linear contact model and rolling resistance linear contact model in the discrete element contact model can be used to simulate the mechanical behavior of sand, and the rolling resistance linear contact model has advantages in simulating the dilantancy of dense sand. Discrete element simulation is carried out for triaxial test of dense sand by using the rolling resistance linear contact model, which verifies the reliability of the rolling resistance linear contact model. Furthermore, the correlations between the meso-parameters such as inter-particle friction coefficient, stiffness ratio and rolling resistance coefficient and the macro-parameters such as peak internal friction angle, residual internal friction angle and peak angle of dilantancy of sand are systematically analyzed. The influence of meso-parameters on shear band width and inclination of dense sand under deviatoric stress is revealed. An empirical formula of shear band inclination angle considering dilatancy angle is proposed. Quantitative relationship between macro and meso parameters of rolling resistance linear contact model is established through research, which providing basis for precisely simulating mechanical characteristics of dense sand by using rolling resistance linear contact model. The flow chart of calibration is given. A method for fast calibration of macroscopic parameters is proposed and verified by an example.

Physical model tests have been carried out in this study, to investigate the effect of fabric on angle of repose in granular piles. On the one hand, particles are deposited at various directions when constructing granular piles, to create different fabric characteristics; on the other hand, several leakage holes are set at the bottom of original (mother) granular piles to construct sub-piles (children piles) such that the effect of internal structures of mother pile on angle of repose can be examined. The results show that the angles of repose, ? and ?, for the mother and children piles, respectively, decrease at first and then increase as the orientation angle ? of deposition plane varies from 0° to 90°, whereas the angle of repose ? ?shows an reverse variation trend. Note that the angle regions, where the minimum ? (or ?) and maximum ? occur, are complementary, respectively being ? = 30° ?45° and ? = 45° ? 60°. The analysis of the basis of a conceptual model leads to the finding that the more the deposition plane orientation approximates to the orientation of potential slipping surface, the smaller the angle of repose is, and the more the deposition plane orientation deviates, the larger the angle of repose is. The fundamentals underlying the observation that ?, ?, and ? have their maximum or minimum values at special angle regions, are clarified. At last, a disturbance zonal model is proposed to account for the mechanism how the position of leakage holes (i.e. internal structure in mother piles) affects the angles of repose ? and ?.

As a typical geological structure, the layered composite structure of surrounding rock is formed by weak interlayer and hard brittle rock, and it significantly affects the stability of tunnel surrounding rock. In the past, the research on composite rock with weak interlayer focused on uniaxial, biaxial or conventional triaxial stress paths, and the mechanical properties and failure characteristics of composite rock at the free face of tunnel under true triaxial stress path were lack of analysis and discussion. In this study, the influence of the thickness of weak interlayer on the mechanical response and failure characteristics of surrounding rock at the free face is discussed based on the composite rock samples with different thicknesses of weak interlayer. The results show that: (1) The thickness of weak interlayer significantly affects the peak stress and strain of composite rock samples. With the increase of thickness, the sliding deformation of rock blocks above the weak interlayer gradually increases, and the compression deformation of the weak interlayer decreases gradually. (2) With the increase of thickness of the weak interlayer, the failure mode of the rock element near the free face of the composite rock sample gradually changes from mixed tension shear failure to tension failure, and the number and failure range of macro cracks gradually decrease, while the rock element far away from the free face gradually changes from shear failure to basically undamaged fracture. (3) The failure areas of composite surrounding rock of side wall with different thicknesses are concentrated on the weak interlayer and the surrounding rock above it, while the surrounding rock below the weak interlayer is basically stable. In terms of stress distribution, with the increase of thickness of the weak interlayer, the maximum compressive stress gradually transfers to the deep weak interlayer, and the tensile stress area gradually decreases, while the depth of the tensile stress area gradually increases.

Double-wheel trench cutter is a professional construction equipment of underground diaphragm wall, and its tooth arrangement system is its core component. The parameter design of tooth arrangement system is closely related to rock breaking performance. In this study, a three-dimensional simulation method for milling rock and soil with milling wheel is developed using the continuum-discontinuum element method (CDEM). On this basis, considering the correlation between free surface and milling, the mechanism of the influence of cutting sequence on rock breaking performance of tooth arrangement system is studied, and a numerical generalization model of rock entry sequence is established under the condition of associated milling, in which the number of adjacent free surfaces is preset as the main influencing factor. The results show that: (1) The curves of milling force and milling depth obtained by milling wheel milling rock and soil mass verify the correctness of the numerical simulation method. (2) Compared with the intact rock mass, the peak load of rock samples with single adjacent preset free surface and double adjacent preset free surface decreased by 32.5% and 68.2% respectively, and the energy consumption of rock breaking decreased by 19.8% and 56.6%, respectively. (3) In the tooth arrangement system, the larger the ratio of the double adjacent preset free surfaces to the total number of picks, the lower the overall energy consumption of the tooth arrangement system, and the energy consumption of the heterogeneous tooth arrangement system is lower than that of the sequential one. The research results provide a basis for improving the rock breaking process and tooth arrangement system optimization of double-wheel trench cutter.

To study the fatigue properties and microstructure variation of salt rock under cyclic loading, uniaxial fatigue tests under different maximum cycling stresses were carried out on salt rock specimens. Meanwhile, scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) instruments were utilized to analyze the microstructure variation in salt rock before and after the test. The results indicated that the cracks growth mode in salt rock under cyclic loading is mainly the development of intergranular cracks, and the number of cracks increases with the maximum stress ratio (the ratio of the maximum cycling stress to the uniaxial compressive strength). After cyclic loading (12 000 cycles), the number of macropores and total pores in salt rock both increase, whereas the number of micropores decreases; and with the increase of maximum stress ratio, the increasing number of macropores and total pores and the decreasing number of micropores both increase. When the maximum stress ratio is 0.40 and the cycle number N≤2 000, the numbers of micropores, macropores and total pores all increase with cycle number; but the increase rate of micropores is faster than that of macropores, showing that the pore structure variation in salt rock is dominated by the initiation of micropores. When the maximum stress ratio is 0.40 and the cycle number N > 2 000, the number of macropores and total pores still increase with cycle number, whereas the number of micropores decreases, demonstrating that the formation of macropores accounts for the main change of pore structure. By solving the inverse function of S-shaped function, an empirical fatigue model with simpler form and fewer parameters was established, which can describe the whole process of irreversible deformation development of salt rock with a unified function, and the rationality of the model was verified by the fatigue test results of salt rock.

Crack monitoring is highly important to understand rock damage evolution. In order to study the characteristics of rock crack propagation and damage deformation, uniaxial compression tests were carried out on standard fine yellow sandstone samples embodied prefabricated cracks with different inclination angles (0°?90°). The 3D-DIC technology was used to obtain the strain distribution of the rock sample in the three-dimensional space coordinates, and combined with acoustic emission, the crack propagation and evolution were monitored from the perspective of optics and acoustics. Therefore, a method for calculating the principal strain of cracks was proposed, which quantitatively characterizes the damage variable D value of rock deterioration. Finally, the influencing factors of determining the characteristic strength of the rock sample by the acoustic emission method and the damage variable D value were discussed. The conclusions are as follows: (1) The principal strain of the crack reflects the time-varying rate and the spatial expansion trend of the homologous cracks during the loading process of the rock sample, which can better characterize the cracking behavior of the rock. (2) The acoustic emission method is suitable for determining the initiation stress of a rock sample, but not for determining the damage stress. The crack initiation stress of damage variable D value lags behind that of the acoustic emission method, but it is suitable for determining the characteristic value of the damage stress. (3) The normalized crack initiation stress range determined by combining acoustic emission and DIC technology is 0.63?0.94, and the normalized damage stress range is 0.83?0.99. (4) Prefabricated cracks will affect the mechanical properties of rock materials. With the dip angle increasing, the crack initiation stress, damage stress and peak stress of the rock show an increasing trend. The initiation of cracks become more difficult because it is difficult to form a local strain field accumulation. The results show that 3D-DIC technology can improve the understanding of rock cracking behavior, and is more important for rock damage monitoring and identification.

To improve the mechanical properties and deformation stability of stabilized sludge, a new type of eco-friendly curing agent with cement, slag, fly-ash and gypsum (CSFG) as materials and fiber reinforcement (FR) is developed. Through the unconfined compression test and permeability test, the effects of different CSFG contents (10%, 20%, 30%), different fiber lengths (0, 3, 6, 12 mm), and different fiber contents (0%, 0.2%, 0.4%, 0.8%) on the mechanical properties and permeability of the samples are compared and further analyzed. In addition, the micro mechanism of the CSFG-FR synergistic effect is analyzed and explored by X-ray diffraction (XRD), scanning electron microscope (SEM) and nuclear magnetic resonance (NMR). The main conclusions are as follows: (1) The mechanical properties of CSFG-FR stabilized samples are significantly improved, and the failure mode has changed from brittle failure to ductile failure. Moreover, the deformation properties are improved, while the improvement effect of permeability is inapparent. (2) The fiber has a critical content (0.4%), which plays a positive role on properties improvement when the fiber is less than the critical content and have a side effect by contrary when it exceeds the critical content. (3) Through forming a three-dimensional fiber network, the fiber can promote the distribution of hydrate and guide the hydrate to adhere to its surface, thus exerting the synergistic effect of CSFG-FR. The optimal fiber content is 0.4% and the optimal fiber length is 12 mm.

Affected by the interface effect, the macroscopic pre-cracking deformation of coal-rock combined body under static compression is significantly different from the coal and rock single body. Based on the effective medium model of rock-like material, this paper considers the composition characteristics of the coal-rock combined body, and proposes a pre-cracking macro-elastic model suitable for different types of coal-rock combined body. The parameters obtained from the test curve are determined by the axial crack strain, which is simple and convenient. The data verification of the existing literature shows the rationality, validity and universality of the model. Moreover, the model parameters are discussed and the following conclusion are obtained: (1) The micro-crack difference can be ignored in the pre-cracking stage of coal-rock combined body. (2) By decoupling the matrix of the coal-rock combined body, the model reflects the impact of interface effect on the elastic modulus of the coal-rock combined body. (3) The effective proportion of the rock matrix decreases significantly with the increase of the coal proportion. (4) There is an optimal ratio of elastic modulus of rock body to coal body, which maximizes the effective proportion of rock matrix. This model can provide a new perspective for mine support scheme design and material selection.

The accurate prediction on the spatial distribution of water inflow and seepage characteristics in the cavern is one of the basic tasks to ensure the safety and economy during construction and operation of the underground water-sealed oil cavern. In order to study the seepage effect of randomly distributed fractures in the surrounding rock of underground water-sealed oil storage cavern on water inflow prediction and spatial distribution of seepage field, a seepage analysis method of fractured rock mass based on embedded fracture element (EFE) is proposed to analyze the three-dimensional seepage field in Zhanjiang water-sealed oil storage caverns. The reliability of the proposed method is validated by the measured data and calculated results, and then the water inflow of the this project during the operation period is predicted. The calculation results show that the EFE model can well simulate the influence of fractures on the local seepage field of fractured rock mass, and reflect the non-uniformity of spatial distribution of the seepage field and water inflow in caverns. The research results can provide references for the precise design of seepage control measurements for water-sealed caverns and the design of sewage treatment facilities during the operation period.

A magnitude of Ms 7.0 earthquake struck the Jiuzhaigou World Natural Heritage Park, in Jiuzhaigou county, Northwest of Sichuan province on August 8, 2017, and trigged abundant coseismic landslides deposit in the scenic spot. Due to the heave rainfall after earthquake, the slope debris flow occurred frequently, which seriously threatened the restoration and reconstruction in the after three years. In 2017?2020, continuous investigation, remote sensing interpretation and in-situ erosion test were used to research the impact of slope runoff erosion on deposit. The result shows that the seepage response characteristics are significant during the scouring process, and the downward movement of wetting front causes the increase of volumetric water content and pore water pressure, the matrix suction first fluctuates slightly and then decreases. In addition, the material characteristics of deposit provides the prerequisites for initiation. Under strong hydrodynamic conditions, the startup process is "preliminary penetration → scraping slip flow → rapid accumulation → local saturation erosion-stability". And finally, the mechanical analysis of deposit under different saturations is more consistent with the field test monitoring results. It is further believed that the increase of soil moisture content, and pore water pressure, the rapid decrease of matrix suction and the erosion of high-intensity runoff caused the initiation. The research results can have a certain significance for the long-term effects prediction of debris flow and ecological management after the earthquake.

In recent years, construction works near the operating metro tunnel in granite residual soil have been gradually increasing, and the impact of these construction works on the safety of shield tunnel should not be ignored. Finite element method is an effective method to evaluate the influence of adjacent construction on shield tunnel, but its reliability highly depends on the reasonable selection of soil constitutive model and parameters. In this paper, the current situation of parameter selection of hardening soil model for granite residual soil is firstly reviewed. Then a back-analysis method for determining the parameters of granite residual soil based on the self-boring pressure meter test (SBPT) is proposed. Finally, the obtained back-analysis parameters are applied to the engineering case of foundation pit excavated overpass existing shield tunnel for method verification, and more reasonable values of parameters of hardening soil model for granite residual soil are determined. The results show that the strength parameters of hardening soil model for granite residual soil can be determined by laboratory tests, and the stiffness parameters of , and are the key parameters for the back-analysis. The ratio of : : from 1:1:3 to 1:1:5 is suitable for engineering practice, and the value of ranges from 36 MPa to 43 MPa according to different ratios.

Coal mining leads to overburden breakage and ground subsidence, and the dynamic evolution process of height of fractured zone could be revealed by the law of overburden and surface migration. Because the ground subsidence lags behind the coal mining, after the mined-out area is abandoned, the height of fractured zone is lower than mining process due to long-term compaction. Based on the characteristics of the subsidence velocity of surface point, the evolution process of the height of fractured zone is divided into two stages. The first stage corresponds to the process of rock layer breaking and gradually passing upward, then the second stage with subsidence of fractured zone corresponds to the process of separation of layers and closure of cracks, deformation and rebound of fractured rock layers after compression, and natural compaction of broken rock masses. This paper focused on the influence of compaction on the height of fractured zone. According to the quantitative relationship between the thickness of coal seam, the rock deformation in caved zone and fractured zone, and the ground subsidence, the prediction model of the height of fractured zone in the second stage was established, which was verified with the actual measurement results of Taiping coal mine. The control variable method is applied to further analyze the evolution characteristics of the height of fractured zone in the abandoned goaf under the influence of each single factor. The results show that the height of fractured zone is related to the uniaxial compressive strength of block in the caved zone, the initial bulking coefficient in the caved zone, the maximum height of fractured zone during mining process and the corresponding height of the caved zone, the depth of coal seam, and the amount of grounding subsidence. After 15 years of mining in Taiping coal mine, the measured value of the height of fractured zone is 11.36?13.00 m, which verifies the reliability of prediction model with predicted value of 12.75 m. Finally, the prediction model was used to carry out theoretical calculations on the height of fractured zone 2002?2003 in the abandoned goaf of Wu’an coal mine (closed mine), combined with ground-airborne transient electromagnetic system to determine the ideal location of ground gas drainage borehole, by which a ground borehole gas drainage test was successfully carried out.

The detailed analysis of disturbance induced by diaphragm wall construction plays an important role in predicting the environmental influence of deep excavations, especially the super-deep excavation. Therefore, this paper collected and analyzed the field data of slurry pressure and concrete pressure during the construction of a 102 m super-deep diaphragm wall. The evolution law and vertical distribution mode of the lateral pressure on the trench wall during the construction were summarized, followed by a new proposed tri-line model of lateral pressure on the trench wall and its validation. The proposed tri-line model can well capture the first increase and then decrease trend of the lateral pressure on the trench, and it can return to the classic bi-line model. Finally, the fine numerical simulation of the construction process of a 102 m diaphragm wall, including the trenching and concreting, was performed adopting both the tri-line model and bi-line model. The stress state and deformation of soils around the trench were analyzed and compared. The results revealed that the construction of super-deep diaphragm walls can lead to the stress redistribution of adjacent soil. The effect zone is about 1.6D (D is the panel length) along the panel direction and about 4.3D perpendicular to the panel. The stress redistribution is controlled by vertical and horizontal transfer mechanisms, and the horizontal transfer mechanism dominates. In Shanghai soft soil area, the concreting would compress the trench wall and increase the trench volume, causing the increase of concrete volume.

In-situ stress is highly important to the safe construction and long-term stability of underground engineering. Acoustic emission method, inelastic recovery method (ASR in short) and hydraulic fracturing method are applied to measure the in-situ stress in the area of 2 005 m shaft construction of Xiling of Sanshandao gold mine. The distribution law of in-situ stress and its abnormal area are obtained, and the principle and application conditions of different in-situ stress testing methods are briefly described. The results show that the horizontal maximum principal stress at different buried depths is always the major principal stress. Meanwhile, when the buried depth increases to a certain extent, the second principal stress changes from the horizontal minimum principal stress to the vertical principal stress. In addition, the results of AE measurement show that the Kaiser effect point of the third principal stress is different from those of ASR and hydraulic fracturing. Furthermore, the variation trends of ?H/?v, ?h /?v and ?H /?h with buried depth are analyzed, and the abnormal area of in-situ stress in the test area is delineated. The study could provide effective data support for the design, construction and long-term stability of the shaft.

It is found that the shear behavior of hard rock is important for the stability of deep rock engineering. In a deeply-buried hard rock tunnel, the splitting of rock results in the spalling or slabbing in the side wall, which can be evaluated by the uniaxial compression test. However, the spalling or slabbing in the arch shoulder and foot is the result of rock failure under shear boundary condition, which should be estimated by the direct shear test. Although a lot of research work on the spalling or slabbing caused by rock splitting have been conducted, there are few direct shear tests on intact rocks to study the shear stress-induced spalling or slabbing. In order to better understand the mechanism of spalling or slabbing, this paper divides the spalling into two forms: splitting failure and shear stress-induced failure under shear boundary, and establishes the conceptual model of two types of spalling based on the statistical results of spalling at Chinese Jinping underground laboratory and numerical results of the deviatoric stress distribution of laboratory section using the FLAC3D. A series of direct shear tests of intact marbles, which can achieve the shear failure and shear slip continuously, is conducted to verify the proposed conceptual model of spalling or slabbing.

Displacement prediction has always been an effective means for conducting the prediction and prevention of landslide disasters. Geotechnical parameters are key input information for landslide deformation calculation, and are rarely considered in the current study. How to conduct the probabilistic prediction of the landslide deformation based on the quantitative characterization of the uncertainties in geotechnical parameters with limited monitoring data is still a prominent difficulty. A case of unsaturated soil slope under rainfall infiltration is investigated and the coupled hydro-mechanical analysis is performed. Based on the spare monitored pore water pressure data, the probabilistic back analysis of geotechnical parameters is efficiently accomplished via the DREAM_zs algorithm. A set of random samples are obtained via the Latin hypercube sampling in accordance with the prior distribution of the geotechnical parameters, and they are utilized to calculate the displacements at the slope toe through the numerical software ABAQUS. Then, a coupled numerical-mechanical displacement prediction model is established through the multiple adaptive regression splines (MARS) and LightGBM algorithm. Based on this model, the displacements at the slope toe are predicted with the stationary posterior samples and the statistical analysis is performed accordingly. It is found that the DREAM_zs algorithm can perform the probabilistic back analysis of geotechnical parameters using limited monitored data with high efficiency and fast convergence. In addition, the proposed displacement prediction model breaks through the limitation of displacement prediction with indirect monitored data such as pore water pressure. And the occurrence probability of slope deformation is also obtained. Furthermore, this study provides a novel idea and attempt for slope deformation prediction.

The traditional geological prediction method of advanced drilling usually takes the change rate of one specific drilling parameter as the main basis for stratum identification. The rock breaking of drill bit is a complicated mechanical process. Stratum identification with single drilling parameter results in great uncertainty. The cooperative effect of multiple parameters in drilling process should be considered. Firstly, the advanced drilling data was preprocessed, including standardization, frequency distribution analysis and sensitivity analysis, to select the key drilling parameters sensitive to stratum changes. Secondly, based on the principles of energy conservation, binary disordered logistic regression analysis and multi-parameter variability analysis, three comprehensive identification indexes of rock breaking energy, logistic regression probability and stratum hardness index were established respectively. Finally, a stratum identification model was established by probability classification method based on Bayesian principle, and the model parameters were obtained by ROC analysis method, and the stratum identification based on multiple drilling parameters and probability classification method was realized. Taking the tunnel project with complex geological conditions as an example, the application of the proposed stratum identification method is introduced. The results show that: Three comprehensive indexes have great performance in cross-hole stratum identification, and the identification accuracy exceeds 80%. The rock breaking energy and the logic regression probability are suitable for the cross-hole stratum identification with short distance, and the average identification accuracies are 86.3% and 84.1%, respectively. The logical regression probability index has strong identification capability for the weak interlayer, and the identification accuracy reaches 94.2%. The stratum hardness index is suitable for the cross-hole stratum identification with long distance, and the maximum identification accuracy of limestone is 93.2%.

Based on the theory of wave propagation in single-phase elastic medium and unsaturated porous medium and Snell's law, the propagation characteristics of P1 wave incidence on wave impeding block (WIB) from unsaturated soil are studied. The analytical solution of the amplitude ratio of reflected wave and transmitted wave of P1 wave passing through the wave impeding block in unsaturated soil is derived. The relation curves of amplitude ratios of reflected wave and transmitted wave with the shear modulus and density of the wave impeding block, angle of incident wave, frequency of incident wave, saturation and other parameters are analyzed, thus the influence laws of these parameters on the vibration isolation effect of the wave impeding block in unsaturated soil are obtained. The numerical results show that the shear modulus and density of the wave impeding block significant affect its vibration isolation effect, and the wave impeding block can achieve better vibration isolation performance when the shear modulus and density of the wave impeding block are within a certain range. The incident angle has a great influence on the vibration isolation performance of the wave impeding block, while the incident frequency has little influence on the vibration isolation performance.

Based on the theory of phononic crystal, a periodically arranged horizontal tube vibration isolation method is proposed, and its vibration isolation performance for subway is discussed. By combining the plane wave expansion method with Bloch theorem, the band structure of the horizontal tube is obtained. A three-dimensional ABAQUS refined model of track-tunnel-soil interaction is established to further verify the damping effect of periodic horizontal pipe on subway vibration. In addition, the influence of horizontal tube material and its related parameters on the vibration isolation band gap is explored. Some laws are revealed. The attenuation region obtained by numerical calculation is consistent with the band gap results of theoretical analysis, and the vibration isolation effect of periodically arranged horizontal tubes on a specific frequency band is significant with a wider vibration isolation frequency band. The attenuation region gradually moves downward with the decrease of elastic modulus. The initial value of vibration isolation frequency band increases with the increase of pile diameter. Additionally, as the axial spacing increases, the upper and lower limits of the attenuation region simultaneously decrease, which also reduces the band gap width of the whole vibration isolation structure. The calculation shows that the frequency band range of periodic horizontal tube under different parameters is within 40?900 Hz.