The strength and deformation characteristics of rockfill materials are related to the initial void ratio and confining pressure. In this study, an elastoplastic constitutive model for rockfill materials is established to predict the mechanical response of rockfill materials under different confining pressures and initial densities. Based on the framework of the Cambridge-type models, the proposed model can account for the transition from dilation to contraction shear response of rockfill materials as the void ratio or the confining pressure increases. The proposed model adopts a micromechanically-based yield function to characterize the evolution of the microstructure with the non-associative flow. A new hardening parameter is derived based on the fact that the virgin compression curves are not unique for rockfill materials. To characterize the state-dependent behavior, a unique critical state surface of rockfill material is assumed. The mathematic requirements for a general Cambridge-type constitutive model are summarized by considering the state dependence; furthermore, both the dilatancy equation and the hardening parameter are modified. A particle swarm optimization method is established to determine the model parameters, and the performance of the proposed constitutive model is verified by comparing with experimental results.

The acoustic emission characteristics of deformation evolution during rock frictional sliding is studied in the present work. Digital speckle correlation method and acoustic emission system were adopted to measure deformation and AE information in the experiment process. The corresponding relationship between the interface frictional sliding rate and the acoustic emission ringing count, the interface frictional sliding displacement and the acoustic emission cumulative energy, the specimen deformation energy density and the AE b-value were studied. The results show that: the evolution of acoustic emission ringing count was influenced by frictional sliding rate of rock interface. There was a close correlation between the sudden change of acoustic emission ringing count and surge of rock interface frictional sliding rate. The acoustic emission cumulative energy was related to the frictional sliding displacement of rock interface. The change trend of frictional sliding displacement of rock interface could be qualitatively identified by the evolution characteristics of the acoustic emission cumulative energy. Based on the evolution characteristics of AE b-values, the interface frictional sliding was dominated by small-scale microcracks of random distribution during the period of slowly increasing shear stress, while the interface frictional sliding was dominated by large-scale microcracks of locking area during the period of shear stress linear growth stage late. The failure of rocks frictional sliding might be caused by small-scale microcracks, and might be also caused by large-scale microcracks of locking area during the fluctuation process of shear stress.

The pore structure and water retention capacity of soils are significantly affected by the cyclic drying-wetting and stress history. To further study the coupling actions of the two factors, water content variation tests were carried out following two different loading paths, i.e., the drying-wetting cycles after vertical consolidation, and the vertical loading-unloading cycles after the air-dried process. The variation tendencies of the water retention capacity and deformation behaviors of soil specimens were explored. The results indicated that the water retention capacity of soil during drying process is significantly different from that during wetting process, and the difference gap tends to decrease with increasing the consolidation pressure. With the increase in the number of drying-wetting cycles, the air-entry values increase while the slopes of the drying phase and wetting phase decrease. These changing tendencies are less significant upon more drying-wetting cycles. As for the soil specimens with different degrees of saturation, with the increase in the pore air pressure, the pre-consolidation pressures of soils are augmented, whereas the areas of hysteresis loop decrease, and hence resulting in decrease in the water retention capacities and deformation. The identical stress states can be reached from two different paths. It was found that the volumetric shrinkage is higher for the soil specimens following the path of drying process after consolidation, and the water retention capacities are lower for the soil specimens following the path of loading after air-dried process.

This study determined the reasonable treatment range of utility tunnel foundation in self-weight collapsible loess with large thickness. Meanwhile, the regularity of the compacting effect on the foundation was revealed with various treatment depths, and the infiltration law and settlement characteristics of composite foundation after immersion were analyzed. With different depths of lime soil (pure soil) compaction piles, the foundation treatment experiments were conducted on the collapsible loess with large thickness. Moreover, post-work immersion tests were carried out by embedding TDR moisture meter and layered settlement instrument. The results show that with increasing the treatment depth of composite foundation, the impermeability of composite foundation, compacting effect and dry density of soil between piles all increase. The external water presents distinct multistage infiltration in composite foundation, including four stages basically. The deformation of wetting soil between piles decreases with the increase of the foundation treatment depth. Besides, it shows obvious five stages. According to the research results, under the condition of effective waterproof measures, the reasonable treatment range is summarized as follows: the treatment depth should be controlled in the range of 9-12 m, and the treatment width should be controlled within 2 m extended from each side of tunnel.

The permeability of calcareous sand has significant influence on the formation of underground freshwater in coral island. Since the contents and occurrence states of fine particles play important roles on the permeability of calcareous sand, it is necessary to analyze their effects and relationships. Permeability tests with constant hydraulic head were carried out on different fine particle contents and particle size combinations of the calcareous sand collected from an island in South China Sea. Results show that the upper bound of particle size affecting the permeability of calcareous sand is 0.075 mm. When the minimum particle size is less than 0.075 mm, the permeability coefficient of calcareous sand is 10?2 cm/s and can be defined as medium permeability according to the permeability coefficient. When the minimum particles size is between 0.075 mm and 0.500 mm, the permeability coefficient is 10?1 cm/s, which shows high permeability. The stable permeability coefficients of the calcareous sand change with the increase of fine particle contents, and the relationship shows as the following: 1) When the fine particles contents are less than 9%, the permeability coefficients decrease slowly with the increase of the fine particles contents. 2) When the fine particle contents are within the range of 9%-24%, the permeability coefficients decrease rapidly with the increase of the fine particles contents. 3) The permeability coefficients tend to be in steady state when the fine particles contents are more than 24%. The fine particle content that affects the permeability coefficient is determined by the pores formed by the skeleton, which reflects the limit value of the fine particle content when the pores are optimally filled. Poor packing or excessive fine particles can result in the migration and loss of fine particles under infiltrate process.

Based on the condition of plane strain and the static equilibrium equations for sliding mass considering strength reduction, the functional extreme-value isoperimetric model of homogeneous soil slope stability in the general case is derived. Based on that the Euler’s equations which must be satisfied when extreme value are obtained by functional analysis, the critical slip surface and the normal stress along the sliding surface are obtained by coordinates transform. Combined with the pre-defined boundary conditions and transversal conditions, the stability analysis for the soil slop is transformed to solving the minimum of a function with four unknown variables including two Lagrange multipliers, safety factor and x-coordinate of the slip end. The minimum of safety factor and the corresponding critical surface can be obtained by analytical computation. By taking the tensile cracks at the top of slope into consideration, the positions of different sliding surfaces and the corresponding safety factors are analyzed through a case study. In addtion, the proposed method is verified by ACADS slope test and the test results indicate that the predicted results consistent with the answer obtained by the judging procedure when the influence of the tensile crack is not considered, while the safety factor is slightly smaller than the answer obtained by the judging procedure when the tensile crack is considered.

Top load of slope caused by vehicle and slope surcharge is an important factor affecting slope stability. Firstly, the mechanical analysis model for rock slope under the top load is established based on the superposed cantilever beam model and the limit equilibrium theory. Then the residual overturning force and residual slip force of anti-inclined rock slope are derived, and the criterion for the failure mode of rock stratum is proposed. Meanwhile, the theoretical method is programmed by Matlab, and its theoretical solution is obtained and compared with the results of the discrete element simulation, which verifies that the proposed model is reasonable. Finally, according to the proposed method, the sensitivity analysis on different parameters is carried out. The results show that the effect of top load is large on the residual force of strata, but is small on the failure mode. The sensitive angles of slope and rock strata greatly improve the slope stability when it is larger than the actual angle value. The interlayer cohesion has a significant influence on the stability of slope with self-weight. The safety factors of numerical simulation and theoretical analysis are consistent, which proves the correctness of the theoretical solution of the flexural toppling failure under the top load. The results can provide references for the stability analysis of similar projects.

The ageing effect of the triaxial undrained shear properties of Nanyang undisturbed expansive soil was studied. Firstly, the undisturbed expansive soil sample was consolidated under the pre-consolidation stress with the conventional triaxial apparatus. The triaxial undrained shear tests were conducted with different unloading ratios (R=0.00, 0.50, 0.75) and unloading time intervals (0, 1, 10, 20, 30 d), respectively. The microstructure features of soil sample was characterized by mercury injection test. Test results show that the mechanical properties of Nanyang expansive soil are closely related to the unloading interval time and unloading amplitude. Under the same axial strain, the deviatoric stress of the soil sample after the unloading process decreases, when the unloading interval (R=0.5 and 0.75) increases. While the deviatoric stress without unloading process increases when R=0. The peak strain of the pore water pressure decreases with the increase of unloading interval. The shear strength of the expansive soil increases linearly with the increase of the intermittent time (logarithmic coordinates) for R=0. However, the strength decreases with the increase of the unloading time interval for R=0.5 and 0.75. Furthermore, it declines fast at the first day (0-1 d) and then becomes slow until stable. Besides, the greater the unloading amplitude is, the smaller the shear strength and modulus are, and the longer it takes to reach a stable state for expansive soil. It is suggested that the slope excavation should be supported timely, and is recommended in the slope stability analysis. The results of mercury test and absorption (discharge) show that the effect of the unloading interval on the shear characteristics of the undisturbed expansive soil is affected by the coupling effect of microfracture development and intergranular cementation.

The application of microbial-induced calcite precipitation (MICP) technology in the soil is mainly affected by the factors: the effective particle size, pore diameter, particle gradation, and hydrodynamic parameters of the particles. The complex pore structure of the soil is difficult to be determined by a single parameter in practical engineering, whereas most of them can be reflected comprehensively by the permeability of the soil. The conditional judgment formulas are proposed for the saturated osmotic grouting with the constant capacity, the step-by-step and low-speed process in this paper. Moreover, with the premise of the size compatibility between the microorganism and the soil particle, the formulas are suitable for MICP method in the soil characterised by the permeability coefficient. Furthermore, the formulas are verified by conducting solidification test, permeability test and strength test on nine types of soil (control particle size 0.040-0.913 mm, initial porosity 31.5%-54.9%) including sand, silt, sandy-clayey purple soil and expansive soil. In the condition of the appropriate value of the permeability reduction parameter ( for cohesionless soil, for cohesive soil), it is showed that the third permeability condition can be applied to all types soil in the tests. In addition, the first permeability condition is more suitable for sandy soil than others in MICP technology. Meanwhile, the formulas of the total volume of grouting solution and the total grouting time are obtained, which provide references for the feasibility assessment of the MICP method and further promotion of this technology.

In order to study the space-time evolution of cemented backfill under applied load, WAW-300 micro electromechanical servo universal test system and DS2 series full information acoustic emission monitoring system were used to monitor the stress, strain variation and acoustic emission activity of cemented backfill specimen during uniaxial compression. According to the stage characteristics of ringing count rate and energy rate, the variation law of acoustic emission parameters during loading the acoustic emission variation is divided into three stages: rising period, calm period and active period, and the space-time evolution law of acoustic emission parameters was further studied. The cemented backfill fracture was predicted using the ringing count rate and energy rate parameters, combined with cusp catastrophe theory. The research shows that: 1) under uniaxial compression, the cemented backfill is ductile failure, and the crack penetration is shear penetration; 2) during the loading process, the cemented backfill evolves from local failure to overall instability; 3) the point mutation theory is used to predict the fracture of cemented backfill, and the fracture prediction model is proposed. The prediction results are consistent with the experimental results. The research results can provide a basis for the stability monitoring and fracture prediction of artificial pillars.

The wetting deformation is one of the leading long-term deformations of the earth-rockfill dam, which significantly influences the stress-deformation behaviours of the dams. In this paper, the rockfill material of weakly weathered granite from the Nuozhadu high earth-rockfill dam was studied by conventional triaxial tests, combined creep-wetting tests, and quick-wetting (without creep stage) tests under different confining pressures and stress levels. The deformation behaviours at all stages of the combined creep-wetting tests were analysed, and the evolution process, characteristics, and mechanism of wetting deformation were investigated. Results show that the wetting deformation of the rockfill material can be classified as the instantaneous wetting deformation and the wet-state creep deformation. The instantaneous wetting deformation occurs during the process of wetting and saturating of the rockfill material and shows non-hardening characteristics. Moreover, the strain increment direction is parallel to the direction of the loading-induced strain increment at the same stress state. The wet-state creep deformation occurs after the rockfill material is saturated and has similar characteristics to the general creep deformation of rockfill materials. The wetting deformation is induced by the weakening of physical state after the rockfill material is wetted by water, and thus the wetting of rockfill material can be considered as a generalised load.

Weak-cemented Xiyu conglomerate, characterized by its with complicated mineral composition and poor cementation, has unstable mechanical properties. In order to reflect the resistance characteristics of surrounding rocks of the diversion tunnel in weak-cemented Xiyu conglomerate, the radial hydraulic pressure pillow test was carried out in Kuitun Water diversion project in Xinjiang province. Meanwhile, based on the traditional bearing plate deformation test results, an elastic model and an elasto-plastic model considering the effect of excavation unloading were utilized to estimate the resistance coefficient of the weak-cemented Xiyu conglomerate. The results indicate that: 1) According to the result of the radial hydraulic pressure pillow test, the unit resistance coefficients of weak-cemented Xiyu conglomerate are in the range of 6.02 to 26.03 MPa/cm. And the unit resistance coefficient in vertical direction is greater than that in horizontal direction. 2) According to the traditional bearing plate deformation test results, the estimated values of the unit resistance coefficient of weak-cemented Xiyu conglomerate surrounding rocks are 7.46-13.54 MPa/cm and 5.00-13.54 MPa/cm using elastic model and elasto-plastic model, respectively. 3) Due to particle composition of Xiyu conglomerate and the ordinary area of bearing plate, the theoretical estimate results of the unit resistance coefficients adopted with the traditional bearing plate deformation test results are lower than that obtained by the radial hydraulic pressure pillow test. 4) The radial hydraulic pressure pillow test results could reflect the resistance characteristics of the surrounding rocks under the influence of multiple factors such as the ground stress environment, the material characteristics of the surrounding rocks, and the loosening effect of excavation and so on. The radial hydraulic pressure pillow test results can provide a direct and reliable comprehensive resistance coefficient of the surrounding rocks for the design of the diversion tunnel excavation or the lining support of surrounding rocks.

A series of modified fluid loss tests was carried out to investigate the hydraulic conductivities (k) of typical sodium treated Ca-bentonite (CaB) and natural Na-bentonite (NaB) contaminated by lead-cadmium (Pb-Cd) and chromium (Cr). The results showed that when the bentonite was exposed to Pb-Cd concentration lower than six mmol/L, its permeability coefficient exhibited a smaller increase by approximately 2 to 3 times, while it increased significantly when Pb-Cd concentration increased to 10 mmol/L. Under the action of potassium chromate, the k of Cr-contaminated sodium-treated CaB sample was slightly lower than that of uncontaminated samples, whereas the k of Cr-contaminated NaB sample was approximately 2 to 8 times higher than that of uncontaminated samples. The results can be attributed to the different forms of chromium existing in bentonite slurry under soil-liquid interaction in different pH-Eh conditions. Since chromium exists in the anionic complex as Cr(VI) in sodium treated CaB slurry, the negatively charged bentonite particles increase, which enhances the dispersed state of the bentonite. In contrast, Cr(III) cation is identified in NaB slurry, which leads to the aggregation of bentonite particles due to the diffuse double layer contraction. A comprehensive analysis was conducted on the variation of chemical compatibility of bentonites under ionic strength obtained from this study associated with those reported in the literature. It is found that a threshold of ionic strength exists, k increases more than an order of magnitude beyond the threshold.

The early concrete hydration not only releases a large amount of heat but also causes the early deformation and constraint stress of the pile, which affects the bearing capacity of piles. However, there are few studies on the effect of formation temperature on the thermo-mechanical properties caused by the early concrete hydration, especially the pile group effect. Field tests were carried out to investigate the thermo-mechanical properties of 3×3 group piles influenced by early concrete hydration. The distributions of temperature and strain of piles along pile depth were measured. Moreover, the heat dissipation and additional stress of piles, and heat dissipation group effect influenced by formation temperature were discussed. Meanwhile, the thermo-mechanical properties of the single pile were also conducted for comparative analysis. The results show that the temperature superposition effect of pile group influenced by hydration heat is not very obvious. The dissipation rate of hydration heat in the constant temperature zone is relatively slower than that in the variable temperature zone. The residual stress of concrete is unevenly distributed along the pile depth, which has large values in the middle and small values at two edges. The maximum residual stress occurs at a depth of 0.6 times pile length.

The effective stress principle of Terzaghi, the foundation of soil mechanics, is widely used in reservoir stress-sensitive research for pore volume and permeability. However, its applicability to the pore volume strain of rock is controversial. Force analysis on porous media with incompressible grains and compressible grains are conducted, and expressions of effective stress for total volume, grain skeleton and pore volume are deduced, which are further compared with effective stress equations proposed by Biot and Skepmton. Then, a new effective stress equation for pore volume strain is established. Finally, the experimental demonstration and application are conducted. The results show that the effective stress is the macroscopic equivalent stress of intergranular beyond the pore pressure in the porous media with incompressible grains. While the effective stress is equivalent stress for the same strain in the porous media with compressible particles. There are three kinds of effective stress equations for total volume strain, particle volume strain and pore volume. The new effective stress for pore volume is related to porosity, compression coefficient of total volume and particles, total stress and pore fluid pressure. The deviations between four theoretical calculations and experimental tests on three kinds of pore media are within 5%. With increasing the total stress quantitatively, the coefficients of pore volume effective stress can be used for equivalently simulating reservoir production with pore pressure dropping. The calculation of the three compressibility equations is convenient and accurate.

Compared with the traditional static load test method, the self-balanced pile test method has the advantages of convenience, economy and adaptability. However, the method is always controversial. To study the difference and reason of load transfer law between self-balanced and traditional static load test pile methods, the laboratory model tests of self-balanced pile, static pressure pile and uplift pile in granite residual soil under the same boundary condition are carried out. Through the resistance strain gauge attached to one side of the pile body, the strain values of the pile body at different positions under various loads are obtained. Additionally, the ultimate bearing capacity of the single pile, the axial force transfer of the pile body, and the distribution of friction on the side of the pile are analyzed. The results show that: 1) In granite residual soil, the self-balanced upper pile and the uplift pile show “sudden” failure when they reach the ultimate load; 2) The conversion coefficient ? of pile side friction resistance in granite residual soil obtained by the model test is 0.573; 3) The ultimate uplift bearing capacity of single pile measured by two loading methods of bottom support and top pull is equivalent; 4) The load is transferred from loading position to the other end of the pile. For each test pile, the distribution of the relatively larger value of the lateral friction resistance is different. For the self-balancing pile and the uplift pile, the positions are concentrated in the bottom of the pile, and for the static pressure test pile that is concentrated in the middle of the pile body.

The dewatering shrinkage cracking of clay has significant influence on human engineering activities. The dry dehumidification test was carried out on the remolded hipparion clay, and the dynamic quantitative data of cracks was obtained by digital image quantitative processing technology. It was found that the evolution law of cracks was different from the traditional law of cracks (the area and average width of cracks continuously increase during the drying process, and finally tend to be stable). For example, the crack of the sample shrunk during the middle of drying process, and the cracks showed the phenomenon of ‘self-healing’. Subsequently, the ‘split-block’ theory was put forward to analyze the mechanism of this phenomenon, and the concept of healing degree was also introduced to study the healing effect of cracks under different initial water contents. The results show that the initial water content has a significant effect on the crack healing degree of the sample. The lower the initial water content is, the earlier the healing occurs and the greater the degree of final healing is. The final healing degree of the sample with a dry density of 1.7 g/cm3 is in a good linear relationship with the initial water content under a temperature of 40℃.

Understanding shear behavior of a sandstone is vital for underground engineering projects, such as mining, underwater tunnel excavation and CO2 geological storage, and so on. In this study, the shear behavior of a intact sandstone under dry/saturated/H2O-injected/CO2-injected conditions were conducted using a shear-flow test apparatus. The results show that the shear strength and the residual shear strength were increase with the effective normal stress under dry/saturated/H2O-injected/CO2-injected conditions. The shear stiffness was also increase with the normal stress under dry condition. The effect of pore pressure on the shear strength follows the Terzaghi effective stress law. Water/CO2 could weaken the shear strength. Water lowered the internal friction angle φ, CO2 hardly affected it. CO2 lowers the cohesion stronger than that of water. The reasons of the weakening effect of water and CO2 were the interaction of fluid-rock, and the weakening effect of water on the clay contained in the sandstone was stronger than that of CO2.

Considering the subway tunnel of Urumqi Metro Line 1 crossing a fault in Jiujiawan, a largescale shear dislocation model test was designed for crossing a normal fault with 60 degree in the segmental lining structure of subway tunnel. Through monitoring and analyzing the key mechanical characteristics of tunnel structure deformation, strain distribution, surrounding rock stress and cracking in the process of fault dislocation simulation, the response law of normal fault with stick-slip dislocation on the tunnel structure was obtained. The results show: 1) Under the influence of normal fault with stick-slip dislocation, the arch springing in the fault is in compression and shear state , while hanging wall arch and footwall vault near the fault are in tensile state of the longitudinal section, and the inner side of the arch and the outside of the wall on both sides of the fault are in the large eccentricity stress state in the cross section. 2) The failure modes of tunnel include oblique crack, longitudinal crack and circumferential crack after the fault dislocation. 3) After stick-slip dislocation reaches 7.0 cm in the normal fault (equivalent to the actual dislocation 1.75 m), the damage zone of the hanging wall tunnel structure is 4.2D (D is the tunnel span), the damage zone of the footwall is 2.4D, and the damage zone of the hanging wall is obviously larger than the footwall.

The treatment process of sludge dredged from East Lake, Wuhan is improved by innovatively introducing the reactive MgO-fly ash cementing materials, based on the combined technology of carbonation-solidification. Through the unconfined compressive strength, X-ray diffraction (XRD), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) tests, the effect of CO2 carbonation on the mechanical properties and microstructure was investigated under water immersion, dry-wet cycles and freeze-thaw cycles. The test results indicate that solidified sludge by reactive MgO-activated fly ash has higher strength and better water stability after CO2 carbonation. After 20-day water immersion, the compressive strength of carbonated samples is about 29% higher than that of non-carbonated solidified samples. The strength of carbonated samples increases slowly with the increase of wet-dry cycles, while the strength of non-carbonated samples first increases and then decreases. The evolutions of compressive strength of carbonated and non-carbonated solidified samples agree well with each other as the freeze-thaw cycles extend, i.e. the strength increases initially, then decreases and finally keeps constant. The microscopic analysis demonstrates that the elongated prismatic hydromagnesite (skeleton construction), flower/bone-like and flaky dypingite and nesquehonite (filling and cementing) are the main carbonation products. In addition, the combined skeleton-filling-cementing effect makes the carbonated samples achieve high strength, good water stability, and strong resistance to dry-wet and freeze-thaw cycles. The continuous water immersion leads to an increasing macropores and transformation of dypingite and nesquehonite to hydromagnesite. The dry-wet cycles also induce the transformation of dypingite and nesquehonite to hydromagnesite, but there is no obvious phase transformation in carbonated samples under freeze-thaw conditions.

The fractional order derivative Kelvin constitutive model is used to describe the rheological characteristics of saturated soils. With continuous drainage boundary, the Laplace transform is used to derive the analytical solutions of the one-dimensional consolidation of soil in the transformed domain. Then the corresponding semi-analytical solutions of the effective stress and the settlement are obtained through inverse Laplace transform based on Crump’s method. The rationality of the proposed solutions is validated by reducing the presented solutions based on continuous drainage boundary to those based on the Terzaghi drainage boundary. Finally, the effects of relevant parameters on consolidation behavior of soil are investigated by the obtained solutions. The results show that the interface parameter reflects the permeability of the drainage boundary, which has an obvious effect on the dissipation rate of the excess pore water pressure in soil. The viscosity coefficient greatly affects the settlement development in the later stage of consolidation, and the larger the viscosity coefficient is, the slower the settlement development is. When ? is not zero, a smaller fractional order α indicates a stronger viscosity, a longer consolidation process and a slower development of secondary consolidation.

30 joint-slices with 10 grades of roughness（JRC=1~20）and 3 kinds of thickness (1.5, 3.0, 5.0 mm) are produced by using 3D printing technology, and then poured into rock-like specimens containing consecutive and filling fracture by moulds. Then the seepage tests are carried out on these specimens with different roughness levels and gap-widths under different confining pressures. The test results show that the permeability of consecutive and filling fracture with different roughness levels and gap-widths decreases with the increase of confining pressure. Moreover, the decrease rate of permeability in the initial stage of confining pressure loading is obviously higher than that in the middle and late periods, and the maximum permeability drop is 78%. In the initial stage of confining pressure loading, when the gap-width is small, the roughness has a great influence on the seepage characteristic of consecutive and filling fracture. While, as the gap-width and confining pressure increase, the effect of the roughness on the fracture permeability rapidly decreases. For all consecutive and filling fracture with 10 grades of roughness, the permeability increases with the increase of the gap-width in the initial and late stages of confining pressure loading. When the confining pressure is small, the larger the roughness is, the greater difference the permeability of consecutive and filling fracture at different gap-widths has. However, with the increase of confining pressure, the difference is gradually reduced. The confining pressure have a dominant influence on the permeability of consecutive and filling fracture, and their relationship can be described by a power function.

At present, all of the theoretical studies about degradation-consolidation of municipal solid waste (MSW) still use the traditional Terzaghi drainage boundary. However, it cannot fully describe the complex drainage boundary conditions in landfills. Accordingly, this paper introduces the continuous drainage boundary into the existing simplified degradation-consolidation model, and then builds a new model of 1D degradation-consolidation of saturated MSW with a fresh surface described by continuous drainage boundary. On this basis, the analytical solution is obtained by solving the characteristic function, and its rationality is preliminarily verified through degradation analysis and convergence judgment. A comparative analysis of the present solution and the existing solutions shows that the distribution of excess pore pressure changes significantly after introducing the continuous drainage boundary condition. Meanwhile, the present solution can solve the contradiction between initial condition and boundary condition, and reflect the time effect of the pore pressure dissipation on the boundary. Further parameter sensitivity analysis indicates that various drainage conditions can be simulated by adjusting the interface parameter, and continuous solutions from complete impervious condition to complete pervious condition are available under boundary conditions. As the interface parameter changes, pore pressure distribution, strain development and consolidation degree development show continuous regular changes. Finally, a feasible strategy of changing drainage conditions is proposed to ensure the stability of landfills based on the characteristics above.

The seismic method based on elastic wave characteristics of rock is the most important method in geophysical exploration. The propagation velocity of elastic wave in rock is an effective bridge connecting physical and mechanical characteristics of rock with geology. In terms of biogenetic coral reef limestone in the sea, the characteristics of elastic wave is an effective way to find out the whole internal properties of coral reef. This study shows that the elastic longitudinal wave velocity of coral reef limestone has a linear positive correlations with dry density and rebound value, but has a linear negative relationship with porosity. The elastic wave features of coral reef limestone with various structural types present significant difference. For example, coral skeleton limestone and coral gravel limestone have good uniformity, whereas coral gravel limestone and coral sand limestone have distinct dispersion. Based on the relationships between longitudinal wave velocity and dry density, porosity and rebound value of coral reef limestone, a classification standard of the quality grade is proposed for coral reef limestone, combined with the rebound values of drilling core along the depth of a coral reef and the optical detection results of core sheets. It has certain reliability and applicability. A modified time-average formula is established by using the basic principle of two-phase rock model. In addition, Remo Hunter-Gardner equation is suitable for elastic wave characteristics of coral reef limestone with different structural types.

Based on the one-dimensional (1D) consolidation equation and advection-dispersion transport equation, this paper presents a solution for coupled self-weight consolidation and contaminant transport in confined disposal of contaminated sediments. The explicit finite difference method is used to solve the transport governing equation, whereas the analytical solution is used to solve the self-weight consolidation equation. In terms of contaminant transport, the proposed solution accounts for advection, diffusion, mechanical dispersion, linear and nonlinear equilibrium sorption, and porosity-dependent effective diffusion coefficient. The proposed numerical solution is compared with the CST1 numerical model to verify its correctness. Using the verified solution, a series of parametric study is conducted to investigate the effects of several important parameters (i.e., consolidation effect, soil compressibility and permeability, and initial contaminant distribution) on the contaminant transport process in the confined disposal of dredged contaminated sediment. The results indicate that the consolidation effect, soil compressibility, soil permeability and initial contaminant distribution have significant impacts on the contaminant transport process in confined disposal of contaminated sediments. Consolidation can greatly accelerate the contaminant transport rate. The contaminant cumulative mass outflow increases largely with increasing compressibility coefficient and permeability coefficient. The rate of contaminant transport is considerably affected by the initial contaminant distribution.

In this paper, the statistical meso-damage theory was introduced to study the deformation and failure mechanical properties of brittle rock in the post-peak region. The limitations and the deficiencies of the damage variables defined by the ratio of the damaged miro-element number to the total number were discussed. The meso-damage evolution mechanism of brittle rock was analysed based on the post-peak deformation and failure characteristics of the heterogeneous rock. The modified damage model was established considering the non-uniformity of the rock material caused by the damaged micro-element. Meanwhile, the function hypothesis of the modified model coefficient was proposed. Then, based on this, the modified statistical damage constitutive model of rock was established, and the methods of determining the model parameters were given. Finally, the theoretical curves of this model were compared with the experimental curves, and the variation law of the model parameters was discussed. The research shows that this model can reflect the different stress dropping rate of brittle rock in the post-peak region. The theoretical curve and variation law of the model parameters are in good agreement with the experimental results, which indicates that the proposed model and methods have certain rationality and feasibility.

The use of hydraulically dredged mud as filling material for land reclamation can not only effectively resolve the shortage problem of ideal filling material such as sand and gravel, but also avoid the negative impact caused by the large amount of dredged mud disposal. However, the hydraulically dredged mud is usually in slurry-like state and has extremely high-water content, low strength and poor permeability. It is difficult to directly access the construction site for the personnel and equipment in subsequent ground improvement. Therefore, this paper proposes a flocculation-solidification combined method for the treatment of surface slurry-like mud to form a working platform. A large number of laboratory tests are conducted to verify the feasibility of the proposed method. First, the reasonable type and optimal dosage of flocculant (PAM) for the flocculation-solidification combined method are determined by syringe titration tests. Then, the flocculation and sedimentation process is simulated through the model tests with different mixing proportions. Vane shear tests are performed to measure the shear strength and water content of the samples at different curing times. The results show that, in comparison with the traditional pure cement solidification method, the flocculation-solidification combined method can enhance the undrained shear strength by more than five times. The results verify the feasibility of the flocculation-solidification combined method.

Due to the concentrated rainfall and severe hydraulic erosion, the loss of the sandy clayey purple soil in Chongqing region is serious. The microbial-induced calcite precipitation (MICP) has been widely used in the soil improvement owing to its low energy consumption and less pollution. In this paper, the culture medium and culture conditions of Bacillus megaterium (BNCC 336739) were optimized by orthogonal tests, and the number of viable bacteria increased by 126% with good activity. Under a water pressure of 9.8 kPa, the soil solidification tests using Bacillus megaterium were conducted to investigate the change rules of solidification effects with treatment times. The results show that calcium carbonate production and dry density increase progressively with the increase of treatment times, and the unconfined compressive strength positively correlates with the calcium carbonate production. The strength tends to be stable with less effective calcium carbonate precipitation and increases by 77% after nine times of treatment. As the pores filled with calcium carbonate and the formation of upper and lower crusts, the permeability decreases continuously and eventually drops by two orders of magnitude. The sample standard deviation (s) of calcium carbonate production (C) in the upper, middle and lower layers of the soil column was used to reveal the discreteness of calcium carbonate distribution. Besides, it is shown that the secant elastic modulus fluctuates with the increase of C under the influence of s. When C is close or s differs greatly, the smaller the s is, the greater the elastic secant modulus is. This study provides scientific basis and reference for the application of MICP technology in foundation, slope reinforcement and soil and water conservation in the purple soil area.

 Soft rocks around deep-buried tunnels under high geo-stress conditions are prone to emerging large deformation. Nowadays, the prediction of squeezing deformation is a significant problem during the design and construction of practical engineering. The existing empirical prediction methods of squeezing tunnels are widely used due to its simplicity and convenience, while they also have many limitations, e.g. most of they can only classify the squeezing degree but can’t predict the exact deformation with considering on a few influencing factors, they were developed based on foreign Q system and not applicable for the BQ system of China. Therefore, a new empirical method, that are available for BQ system, is proposed based on more than 100 deformation monitoring data of squeezing tunnels. The method could synthetically take many factors into account, such as tunnel depth, span, ratio of rock strength stress and initial stress, groundwater and structure surface of rock. The proposed method is verified through comparison and analysis of monitoring results of several tunnels with large deformation, and plays a very important guiding role in determining the strength of the support and applying advance reinforcement measures.

Considering semi-permeable boundary condition and Terzaghi-Rendulic consolidation theory, the dissipation solution of excess pore water pressure and the ground surface consolidation settlement are obtained by using the conformal mapping and separation variable method. The analytical results are compared with the measured results from project cases, which shows good agreement. In addition, the influence laws of the soil consolidation settlement and the excess pore water pressure are obtained via the parameter analysis. The results show that the larger the permeable ratio of soil and lining is, the larger the initial rate of consolidation settlement is, but it has no influence on the final convergence value. The smaller the elastic modulus of soil is, the larger the final consolidation settlement is. The excess pore water pressure gradually increases with time, while it dissipates on a large scale in a short time after the excavation of the tunnel. The speed becomes slow when the value reaches to about one-tenth of the initial value. The longer the distance to the lining is, the smaller the initial excess pore water pressure is, and the slower the corresponding dissipation speed is.

The results of professional monitoring implemented in 2006 shows the Muyubao landslide in Three Gorges reservoir area has been continuously deformed, which brings a huge threat to the Three Gorges Dam Project and the Yangtze River Channel. Qualitative analysis indicates that the reservoir water level plays a key role in the surface deformation of the landslide. Through many field geological survey data, long-term on-site inspection, artificial GPS displacement monitoring data, and automatic monitoring data for nearly one year, the deformation characteristics, evolution law and deformation mechanism of the landslide under reservoir water fluctuation and rainfall conditions are analysed in depth. The results show that the geological factors such as landslide slope structure, lithology and geological structure control the deformation of Muyubao landslide, and the reservoir water level is the main driving factor. During the rise of the reservoir water level, when the reservoir water level rises from 145 m to 155 m, the monthly displacement is the minimum; when the hydrodynamic pressure is towards inside slope, the landslide deformation is the smallest; when the reservoir water level rises from 155 m to 175 m, the reservoir water infiltrates the front slope, which leads to form a floating weight-reducing effect on the anti-sliding section in front of the landslide and increases the deformation. When the reservoir water level reduces from 175 m to 170 m, the monthly displacement reaches the maximum value and the cumulative displacement forms a step, which is affected by the dynamic water pressure and the floating weight loss effect of the slope. When the reservoir water level decreases from 170 m to 145 m, the floating weight loss effect is reduced and the monthly displacement is reduced. At present, the deformation trend of the Muyubao landslide is less, and the possibility of large-scale sliding is smaller, but the monitoring and mechanism research must be further strengthened.

It is significant to study the stability of ancient city wall for its conservation and restoration under the environmental and human destruction conditions. In this study, the current preservation situation of Yulin City Wall (YCW) were investigated, and the mechanical properties of masonry structures and rammed soil in city wall were tested by in-situ tests and laboratory experiments. The overall stability and stress-strain state of the city wall were analysed with numerical method when the brick-clay structures turned degraded, and the embedded buildings were demolished. The research results show that: 1) The safety factor is smaller than the design value of 1.3 when the average water content of the rammed soil is larger than 11.5% during the rainfall infiltration stage or the denudation length of rammed soil at the top of the city wall larger than 2.5 m. However, the degradation of masonry structures has little effect on the stability of the city wall, which indicates that the strength of the rammed soil plays a determining role on the overall stability of the city wall. 2) The plastic zone almost extends to the top of the city wall, when 2 or 3-storey high buildings embedded 3.0 m depth or 1-story high buildings embedded 2.5 m depth in the bottom of the city wall are demolished. 3) The plastic zone may extend to the top of the city wall and will collapse, when the penetrative door with the width larger than 4.0 and 1-storey high building with the width larger than 2.5 m are demolished, respectively. It has no influence on the stability of the city wall, when the penetrative buildings with the section size smaller than 2.0 m×2.0 m are demolished.

For the large open-pit mining, there is still a large amount of residual coal in highwall mines. However, the reasonable width of rib pillar is always a difficult problem, which has greatly restricted the high-efficiency application of highwall mining system. The working faces in highwall mining were assumed as a series of co-linear cracks with certain spacing interval. Based on theⅠ-Ⅱ composite crack model in fracture mechanics, the stress distribution at the edge of rib pillar was analyzed, combined with Hoek-Brown failure criterion and Mohr-Coulomb failure criterion. Besides, the boundary equations of damaged zone at the edge of rib pillar were established. Accordingly, the calculation formulas of damaged width of rib pillar were obtained under different failure criteria, respectively. The curve laws were presented on the basis of the theoretical formulas of damaged width of rib pillar under different failure criteria and three sets of characteristic parameters for determining different states of coal body damage. According to the curve laws under different failure criteria, the effects of independent factors, such as the width of retaining coal pillar, , the width of cavern, , burial depth, H, and the dip angle of coal seam, ?, on the damaged width of rib pillar, , were analyzed. Meanwhile, the data of field tests were substituted into the theoretical formulas under different criteria. The theoretical results and measured data showed that the mutative laws obtained by applying the Hoek-Brown failure criterion accorded with the evolutional laws of rib pillar damage of actual field better, and the application of Hoek-Brown failure criterion was more suitable for the analysis of fracture of jointed rock mass. In addition, the mechanism and process of rib pillar destabilization were described by considering the limit failure theory and the asymptotic failure theory in the stability study of coal pillar. This paper provides a new approach to calculate the reasonable width of rib pillar and the application of criteria in theoretical analysis of pillar failure, which is significant for popularizing the highwall mining technology.

The failure to characterize subtle difference would occur when the existing available methods were used to identify the structural domain boundaries of rock masses at underground mine. Here, research on the three-dimensional refined demarcation of homogeneous structural domains of jointed rock masses at underground mine was carried out, and geological survey data of the No. 3 block of the Zn polymetallic orebody in Tongkeng Mine (China) was used to demonstrate the validity of the method. In view of the spatial structure of jointed rock masses, a three-dimensional structural network model of the jointed rock mass at the underground mine was built based on the coupling of deterministic-stochastic discontinuities, and the model was subsequently discretized with orthogonal meshes. The values of the blockiness levels of the meshes were adopted to determine the homogeneous structural domain boundaries. The K-means clustering algorithm was used to test the similarities of data sources (i.e., meshes), and the sum of squared error (SSE) was employed to measure the quality of clustering. Finally, the rock mass structural domains were reconstructed from the perspective of three dimensions, and the method to three-dimensionally demarcate the homogeneous structural domains of rock masses was consequently formulated. The result shows that the method could accurately divide the structural domains of rock masses in three dimensions and provide a beneficial reference to the subsequent research works (e.g., rock mass quality evaluation and DEM simulation).

Since the catastrophe of the red-bed soft rock is closely related to the water-rock interaction on the surface, the research on the interface process is of great significance to reveal its catastrophic mechanism. However, at present, the study on the red-bed soft rock softening mainly focuses on the macroscopic phenomenological characteristics, and the study on its interface process is still in the exploration and initial stage, which needs further improvement. The characteristics of the interface process of the red-bed soft rock softening are analyzed, which shows the soft rock particles on the water-rock interface are continuously dissolved, and the water diffuses in the soft rock to form a new water-rock interface. Based on this result, the standard entropy of soft rock is established to characterize the soft rock softening, and the evolution of the standard entropy is consistent with that of the softening and disintegration of soft rock over time. At the same time, the dynamics model of soft rock softening interface is constructed by using the Fick diffusion law, which can describe the formation rule of the water-rock interface well. Finally, in the DEM-CFD model of red-bed soft rock, the particle connection fracture in soft rock softening process represents the generation of water-rock interface. Comparing the dynamics models of the interface process, a better fitting result is achieved. The results of this study have certain significance for the exploration of soft rock softening interface.

The train is simulated by a multiple-mass-spring-damper model, and the bridge vibration is solved by incorporating the slab track kinematic equations into the bridge model. Combined with pile-group foundation model, a semi-analytical coupling model of train-rail-bridge-bridge pier-group pile foundation is established. Based on the Fourier transform and the Green function of elastic half-space in the frequency domain, the ground wave field caused by the moving train on viaduct is obtained. The vibration laws of the upper stiff-layer and lower soft-layer ground and the upper soft-layer and lower stiff-layer ground are studied. Moreover, the effects of pile diameter and pile length on ground vibration attenuation are analyzed. The results show that the vibration of the upper stiff-layer and lower soft-layer ground at the center of the track is larger than that of the upper soft-layer and lower stiff-layer ground at lower vehicle speed; but the vibration of the upper soft-layer and lower stiff-layer ground increases significantly when the vehicle speed is close to the shear wave velocity of the surface soft soil, which indicate that the speed of the train should be avoided to approach the shear wave velocity of the surface soil. The vibration at the center of the track increases with the increase of the pile length and pile diameter, especially when the vehicle speed is large. The pile has a good damping effect, and the ground vibration attenuates rapidly due to the geometric damping and pile scattering effects within the pile-group area. The vibration attenuation speed is faster when the pile diameter is larger, but it is less affected by pile length. The ground vibration amplitude of the upper stiff-layer and lower soft-layer ground on the outside of the group pile foundation is smaller than that of the upper soft-layer and lower stiff-layer ground, which indicates that the effect of the upper stiff-layer and lower soft-layer ground on vibration attenuation is better. Rational design of pile foundation can meet the vibration control requirements at the center of the track and effectively reduce the environmental vibration around the viaduct.

The numerical analysis method is an important method to study the stability of the slope reinforced with anti-slide pile, which can take both the mechanical behavior of the anti-slide pile and the stability of the slope into consideration at the same time. However, in the previous numerical simulation, it is hard to find a numerical model of the anti-slide pile with easy modeling, high precision and low time cost. Therefore, an anti-slide pile model coupled with the composite solid-structural element is proposed in this study. Based on this model, the influence of design parameters such as pile location and space on the stability of slope reinforced by composite anti-slide pile are studied under the free and fixed constraints of anti-slide pile top. Besides, the potential failure modes of anti-slide pile is also studied. The results show that the proposed model can realistically simulate the mechanical properties of the pile with a high calculation accuracy, and the calculation results are independent on the mesh density. When the anti-slide pile is arranged in the middle of the slope, the safety factor of the reinforced slope reaches to a maximum value. The closer to both ends of the slope, the smaller the safety factor of the reinforced slope. When the pile space is less than 3D, the potential sliding surface of the slope is divided into two independent parts, and the soil between the piles forms an obvious stress arch. When the pile space is larger than 4D, the plastic shear zone of the center soil between the piles completely penetrates, and the soil between the piles forms the reverse stress arch. When the anti-sliding piles are arranged in the middle ( 0.5) and in the lower part of the slope ( 0.3) with the free and fixed constraints in pile top, respectively, the anti-sliding pile is easy to bend and damage. The results have guiding significance for the engineering design of slope reinforced with anti-slide pile.

Based on the research of unsaturated porous media, the propagation characteristics of Rayleigh waves in unsaturated soil are studied by considering the interaction between liquid and gas phases in the pores. The elastic wave equations are established using the mass balance equations, the momentum balance equations and the effective stress principle of the unsaturated soil. The dispersion equations of Rayleigh wave in unsaturated soil are derived by introducing potential functions and combining free permeable and breathable boundary conditions. Finally, the effects of saturation degree, frequency, and intrinsic permeability coefficient on the wave velocity and attenuation coefficient are discussed by numerical examples. The results show that the trend of wave velocity is first unchanged with the frequency and inherent permeability coefficient, then decreases slightly, then increases sharply, and finally becomes consistent at different saturations. Moreover, the attenuation coefficient first increases with the increase of frequency and then decreases with the increase of the intrinsic permeability coefficient at different saturations.

Based on the wave motion principle, the impedance ratio and sublayer period ratio were extracted as basic variables to characterize the regularities of fundamental periods under different site conditions. The concept of sublayer contribution coefficient was put forward, which can be definitely determined by the two basic variables selected. Thus, a general relationship among the coefficient, impedance ratio and period ratio was established. A simple and practical method with clear physical significance was proposed to estimate the predominant period of stratified sites by using the sublayer periodic weighted cumulative technique. Taking the transfer function results as standard values, overall comparison of the proposed method with available simplified approaches was carried out under 240 calculation conditions, and the deviation analysis and applicability evaluation of different methods were given accordingly. Results show that the impedance ratio and sublayer period ratio were suitable as characteristic variables for site period research. The traditional method with simple summation of sublayer periods cannot reflect the effect of soil layer structure on the site period. Its relative deviation may reach more than 40% for the most common progressive hardening sites, and the deviations can easily be great than 20% for situations with extreme soft interlayer. Hadjian’s method exhibits an obviously higher accuracy than the classical method, while the method itself and its parameters lack clear physical meanings. The maximum relative deviations are always less than 8% for the proposed method under general and extreme situations, and the case proportions with deviation less than 5% and 2% are above 85% and 60% respectively, significantly higher than those of Hadjian’s method. The results strongly reveal that the new method fully meets the engineering accuracy requirements, and can be promoted in practical engineering.

Numerical simulation of the dynamic process of Nomash River debris flow was carried out using the continuous theory method in this study. Three different entrainment rate models were applied in the continuous theory model, and the HLLC approximate Riemann solution was used to calculate the interface flux of the control unit of the finite volume numerical discrete. Calculation results of disaster scope and motion time were in good agreement with the actual disaster situation, which verified the correctness and validity of the simulation. Then, the final accumulation depth, motion velocity and erosion depth were analyzed and discussed. The results showed that the average depth and maximum depth of final accumulation obtained using McDougall entrainment model were close to those measured. The maximum velocity obtained using the Medina entrainment model at each time was the largest, followed by the result of McDougall entrainment model and the result of Pitman entrainment model. The erosion depth distribution using McDougall erosion model was more continuous, and the maximum value of 8.1 m was close to the estimated value of 8 m. The erosion depth results obtained using Medina erosion model and Pitman erosion model were more dispersed, and their maximum values were 10.9 m and 8.6 m, respectively.

The response displacement method (RDM) is recommended by Code for seismic design of urban rail transit structures (GB 50909?2014). However, this RDM method has certain limitations in the seismic analysis of underground structure. Based on the theory of RDM, the generalized response displacement method (GRDM) is proposed for seismic analysis of underground structures with complex cross-sections in this paper. Firstly, based on the substructure analysis method, this paper theoretically proves the consistency between RDM and GRDM and also introduces the mechanics model and implementation steps of GRDM in detail. Then, in combination with an actual tunnel structure with horseshoe cross-section, the validity and accuracy of the proposed method for calculating different areas of generalized sub-structure is verified under different seismic intensities, based on the dynamic time history analysis method. The analysis results show that the proposed method is a simplified analysis method with simple operation, high precision, and strong practicability, which can be used in the seismic analysis and design of the underground structures with various complex sections.

Perforation provides fluid conduit between wellbore and reservoir, hence it is an important controllable parameter for hydraulic fracturing stimulations. Focusing on the mechanism of fracture growth from perforation to near-wellbore in horizontal wells, a hydro-mechanical coupling model was used to analyze the stress change, together with continuum-based damage elements to characterize the three-dimensional fracture propagation and geometry evolution. A finite element program was developed to investigate the effects of perforation on fracture initiation pressure, failure location and near-wellbore fracturing complexity. The model was validated against the results of analytical model and perforation fracture experiments. The simulation results of horizontal well fracture initiation pressure were coincided well with the records of field test. The results indicate that: perforation can be used to control the fracturing pressure and propagation behavior of the initial fracture, which has a further effect on the fracture geometry of near-wellbore region in horizontal wells. Optimizing perforation parameters can lead initial fracture extend toward the preferred fracture plane. The results could help to decrease the fracture pressure, reduce the tortuosity and complexity of near-wellbore fracture caused by the helical perforations, and improve the fracturing stimulation effects of tight oil and gas reservoirs.

The full field three-dimensional digital image correlation (3D-DIC) system is introduced, the system comprises three groups of the 3D acquisition units setting around the cylindrical specimen to cover the maximum surface area as much as possible. The speckle images are collected during test and used to analyze the deformation of the specimen. For verifying the reliability of measured results of the 3D-DIC system, the constant strain rate and alternative strain rate tests are conducted with Emochi andesite in uniaxial compression, the results are coincident with each other by comparing the measured results of 3D-DIC and strain gage, which indicates that the 3D-DIC system can meet the requirements of non-contact and visual deformation measurement of rock mechanics test. Moreover, taking Tage tuff as object, the evolutions of displacements and strain fields are obtained by images analysis, the non-linear and localized deformation of specimen are observed at the same time. The results indicate that it is more effective to study the rock deformation by using 3D-DIC method than that by using conventional methods. The 3D-DIC system provides a new and advanced test method for investigation of rock mechanics.

Based on the high-resolution borehole image obtained by digital panoramic borehole camera system, a method for recognizing solution fissure based on color features was proposed. Considering the fact that typical rock mass structure, such as soil layer and solution fissure have obvious difference from common rock layer in color, a self-adaptive detection model based on HSV (hue- saturation-value) color space was established. The binarized image of solution fissure was obtained using this model. Secondly, the binary image was filtered to avoid the noise effects. Then, the binarized image of solution fissure was divided and the density of pixels in each segmentation was calculated to determine the depth, area and direction of the soil layer and the solution fissure, so that the identification of solution fissure in the digital borehole image can be achieved. Through verifying this method with many actual borehole images and comparing them with the corresponding borehole radar images, the results indicate that this method can identify all the solution fissure and the soil layer throughout the whole borehole digital optical image automatically and quickly. It provides a new reliable method for the automatic identification of borehole rock structures in practical engineering.

It is difficult to solve the problem of multi-results when using ground penetrating radar (GPR) to forecast geological anomalies of karst tunnel due to numerous factors, such as the field detection environment, the complexity of karst geology and the interpretation technology and so on. Some representative cases from the previous projects were chosen as the studied object, the attribute characteristics of typical geological anomalies in karst tunnel construction were analyzed and summarized. The results of field tests indicated that the attribute characteristics were closely associated with karst geological anomalies. Among them, the center frequencies of GPR reflection waves in cavity karst caves, karst caves filled with dry loose clay and gravel and anhydrous fracture zones attenuated slowly with time, and the distribution ranges were 90-105 MHz, 85-100 MHz, and 70-110 MHz respectively. However, the center frequency of radar reflection waves in karst caves filled with soft plastic clay and water-saturated fracture zones decreased rapidly with time, and the distribution ranges were 60-80 MHz and 40-70 MHz respectively. After studying the method of quantitative representation for attribute features, a calculation method of radar wave absorption and attenuation parameter based on generalized S transform and wavelet spectral simulation was proposed. The analysis results of field tests indicated that each of the characteristic properties could reflect the features of the radar reflection wave of karst geological anomalies in some ways. Different geological anomalies in karst tunnel construction could be distinguished after integration of these characteristic parameters, which could enhance the accuracy of GPR interpretation in karst tunnel advanced geology prediction.