In order to study the softening characteristics of gravel-geogrid interface during and after cyclic shearing, a series of displacement controlled monotonic direct shear tests, cyclic direct shear tests with 2 000 cycles and post cyclic direct shear tests were carried out on the gravel-geogrid interface using dynamic direct shear apparatus. The shear strength characteristics, volume change behavior, shear stiffness and damping ratio of the gravel-geogrid interface under four groups of normal stresses of 20, 40, 60 and 80 kPa were studied. The direct shear characteristics of the gravel-geogrid interface before and after cyclic shear were compared and analyzed. The results show that: in the cyclic direct shear test, the average peak shear stress of gravel-geogrid interface first increases and then decreases, and finally tends to be stable with the increase of number of cycles, and the interface shows shear softening characteristics; the vertical displacement increment of gravel-geogrid interface decreases gradually with the increase of number of cycles; the shear stiffness first increases and then decreases with the increase of number of cycles, and finally tends to be stable; the damping ratio first decreases and then increases with the increase of number of cycles, and finally tends to be stable; under the same normal stress, the peak shear stress increases and the residual shear stress decreases in the cyclic direct shear test compared with the monotonic direct shear test; the cyclic shear makes the interface cohesion increase significantly and the internal friction angle decrease.

The unsaturated hydraulic characteristics of wasted soil is the basis for predicting and evaluating the migration and distribution of leachate in landfills. Based on the aerobic ecological restoration project of the Beiyangqiao Waste Landfill in Wuhan, an on-site pumping water injection test was carried out, and the effects of using different theoretical methods on the calculation results of permeability were compared in this paper. It was inverted by monitoring the water level change data of the pumping test and unsaturated hydraulic characteristics of wasted soil. The results show that the saturated permeability coefficients of the obsolete landfills tested in the field test are all in the order of 10?6?10?5 m/s, and different test methods have little effect on the saturated permeability coefficient test results. According to pumping test results, it is inferred that the pumping influence radius is about 15 m, and the single well flow rate is 0.3 m3/h; the average residual water content of the wasted soil is 27%, which is larger than the measured value from indoor tests. The air intake value of the wasted soil is 2 kPa and the pore size distribution index is 1.20. The results are similar to the indoor test results. The on-site pumping test can not only directly evaluate the water conductivity of the garbage, but also accurately estimate the effective soil-water characteristics of the waste with the help of numerical inversion methods, which provides a new method for obtaining unsaturated hydraulic characteristic parameters.

The adhesion property of slurry-soil interface is the key issue of fissure reinforcement and earthen sites repair, and the shear strength is a key index to evaluate the adhesion property of the interface. In order to investigate the influence of SH-(CaO+F+C) slurry, interface roughness and number of lime piles on the adhesion property of slurry-soil interface in the fissure grouting system of earthen sites, the wave velocity and shear behavior of slurry-soil interface (interface failure mode, shear stress-strain curve and ultimate shear strength) with different ages and grouting modes are analyzed by indoor direct shear tests. The results show that shear strength of the interface formed by four grouting modes increase with the increase of ages, and reach stable by 63 days under the influence of the mixed slurry combined of quick lime, fly ash and modified polyvinyl. The main failure mode of the interface among all ages is the bonding failure; in addition, the thickness of the residual soil on the surface, the peak shear stress and the equivalent shear coefficient of different reinforced interfaces can be arranged in a descending order as follows: grouting with lime piles and grooves, grouting with grooves, grouting with lime piles and grouting alone. The above phenomenon are caused by different combinations of infiltration, expansion and compaction, heating, mechanical occlusion and ion migration mechanisms.

On the basis of the existing research on the pot cover effect, the law of the water accumulation caused by the pot cover effect is studied for the road surface and runway, which have a structure of cover layer (equivalent to "pot cover"), gravel layer, and clay layer from top to bottom in actual engineering. Through carrying out indoor tests to simulate the road foundation structure of the actual project, the law of the water accumulation in soil, under the two conditions of open and closed, was analyzed respectively. The test results show that there is a phenomenon of water vapor circulation of the pot cover effect under the two test conditions, and the peak values of the water head circulation of the two tests are different. The internal mechanism of water vapor circulation was explained by the calculation of the water heads value. Calculating the circulating water volume of the closed system verified that the circulating water volume generated by the two tests in half of the cycle is approximately equal. It is found that the law of the water accumulation caused by the pot cover effect is related to whether the bottom of the gravel layer is flat. If the bottom of the gravel layer is not flat, the water in the gravel layer will keep accumulating. If the bottom of the gravel layer is flat, the water in the gravel layer just increases to a certain amount, the water volume will no longer increase, and a certain amount of water circulates in the form of water vapor in the gravel layer. Favorable road foundation structure should be designed in the project to prevent massive water accumulation under the road surface.

Affected by excavation disturbance or in-situ stress, the heterogeneity of surrounding rock is universal. Therefore, treating the permeability as a constant will reduce the accuracy of water inflow prediction. In view of this problem, a calculation model of water inrush in tunnel considering the heterogeneity of surrounding rock is constructed. Based on the equilibrium differential equation for seepage and Darcy's law, the calculation formula of water inrush and external water pressure of the structure is derived. Taylor's formula and its series expansion are used to degenerate and verify the analytical formula, and then the applicability of the formula is also analyzed. Finally, this model and the formula derivation are verified by comparing results with the measured data. Research shows that the decrease in the excavation disturbance can reduce the variability of the permeability of the surrounding rock of the tunnel, which can improve water resistance of the tunnel. Considering the influence of excavation disturbance on the permeability of the surrounding rock, the calculation error of the water head height at the outer edge of the supporting structure can be reduced from 14% to 6%. Considering the influence of ground stress on the permeability of the surrounding rock, the calculation error of water inflow can be reduced from 18.2% to 10.6%, which improves the prediction accuracy to a certain extent.

A system failure probability analysis method of cohesive slope considering the spatial variability of undrained shear strength is proposed. In this method, the local averaging parameter of the random field of undrained shear strength on slip surface is introduced as an equivalent parameter. The statistical characters of the equivalent parameter and the correlation coefficient between different equivalent parameters are formulated. Then, the reliability index of a single failure mode and the correlation coefficient between different failure modes are calculated based on the equivalent parameters. By considering both the reliability index and correlation coefficient between different failure modes, the representative slip surfaces are searched step by step, and the system failure probability is assessed using those representative slip surfaces. Finally, to verify this method, three slopes are analyzed as examples. The results show that the equivalent parameter obtained by local averaging along the circular slip surface is feasible to describe the spatial variability of the undrained shear strength, and the proposed method can assess the system failure probability of cohesive slope with small error. Meanwhile, the correlation coefficient between failure modes increases with the spatial correlation of the random field, thus the number of representative slip surfaces required to achieve convergence will reduce.

In order to study the evolution law and physical mechanism of permeability performance of compacted clayey soil-rock mixtures, a series of dynamic compression tests and triaxial permeability tests were conducted. The compaction curves of soil-rock mixtures show obvious unimodal patterns similar to those of pure clayey soils when rock content CR < 70%. When CR > 70%, the compaction effect begins to decline. A peak for the maximum dry density of the mixtures can generally be achieved when the CR is around 70%. In addition, increasing CR will decrease the optimum water content of the soil mixtures, but this almost does not change the water content of clay matrix at the optimum compaction state. Clay matrix can be compacted to the densest state when CR < 30%, beyond which the clay matrix void ratio gradually increases. When CR > 70%, the clay matrix void ratio presents a sharp increase. The permeability shows constant or a slight decrease as the rock content increases from zero to about 30%. The lowest permeability can be achieved when CR is around 30%. Beyond this amount, the permeability coefficient increases rapidly with a further increase in rock content. Based on the soil-rock meso-structural distribution and clay matrix void ratio, a concept model for flow path in clayey soil-rock mixtures was proposed. The flow path in compacted soil-rock mixtures can be divided into four kinds: low permeability path in compacted clayey soil matrix, ultra-low permeability path in compacted clayey soil matrix with gravels, medium permeability path in soil-rock interfaces, high permeability path in skeleton voids of rock aggregates.

Water retention curve (WRC) is an important tool to study the hydraulic and mechanical properties of unsaturated soils, such as permeability, strength and deformation properties. Most of the existing WRC models fail to reflect the water retention mechanisms of unsaturated soils or they are complex in form, and these models are hard to give good performance on modelling the bimodal and multimodal WRCs. In this study, based on analyzing the water retention mechanisms of unsaturated soils, the WRC was divided into two domains that are governed by adsorption and capillary mechanisms, respectively. An adsorption water retention curve model (WRCM) was developed based on micro-pore filling theory and Kelvin’s law. A capillary WRCM was established based on the capillary condensation theory and Young-Laplace equation. Then, a new water retention curve model over the full suction range was built by superposing the adsorption and capillary WRCMs. Finally, the new model was validated through modelling the experimentally measured WRCs of six representative unsaturated soils, including Shanghai soft clay, Xi’an loess, Nanyang expansive soil, Guilin lateritic clay, Western Liaoning aeolian soil and Inner Mongolia Gaomiaozi (GMZ) bentonite. Results showed that the proposed model, which was simple in form with definite physical meaning parameters and successfully reflected the adsorption and capillary mechanisms of water retention, was able to simulate WRCs with different shapes for different types of soils under different conditions.

The study on influence of loading rate on mechanical behavior of Zhanjiang clay, which is a kind of sensitive clay with high yield strength, could be noteworthy. In order to study the loading rate effects on intact mechanical properties of Zhanjiang clay, the self-boring pressuremeter tests (SBPT) under five different loading rates have been carried out. The influence of stress rate on undrained shear strength, linear stiffness and non-linear degradation of shear modulus of the soil have been discussed. It is shown that the greater stress rate results in higher undrained shear strength, proposing strong linear correlation between two variables, and that behaves differently from the results of tests controlling strain rate given in literature. The linear secant shear modulus G_ur increases with stress rate and the undrained shear strengths varies within a class with small width after normalized by corresponding G_ur, which indicates little effect caused by loading rate on the strain corresponding to the peak strength. The significant degradation of tangential shear modulus G_t, at higher gradient and the steeper G_t-γ decay curve have been observed when at higher stress rate. The value of shear strain where G_t decreases to less than G_ur is about 0.1% for all stress rate conditions. The loading rate significantly affects the amplitude and the gradient of the decay of G_t in the corresponding class. The smaller the stress rate leads to the lower strain level where the decay of G_t mainly occurs. It is recognized that the special microstructure could account for the loading rate effects of Zhanjiang clay and this comment is preliminarily proved by super-mini-penetration tests conducted on both undisturbed and remolded samples. It is recommended that special attention should be paid to both the loading rate effects on in-situ mechanical properties and the influence of “loading rate history” on creep behavior of soils.

In order to understand the deterioration of physical and mechanical properties of high-temperature rocks, and the related microscopic characteristics after water-cooling during the thermal reservoir construction, uniaxial compression tests were conducted on five groups of granite samples, which at normal temperature and 200, 400, 600, and 800 ℃ had experienced water-cooling shocks, respectively. Ultrasonic testing, XRD and polarizing microscope observation were adopted to analyze the microscopic failure mechanics of rocks. Results show that with the increase of rock temperature, the peak strength decreases gradually with an increase of the peak strain, and the failure mode changes from sudden brittle failure to progressive failure. The mass loss rate, volume expansion rate, and density reduction rate increase with the increase of temperature, except for the ultrasonic wave velocity. The volume expansion rate of cooled rock samples increases significantly when the temperature ranges from 400 ℃ to 600 ℃, and the attenuation rate of wave-velocity of rock samples decreases when the temperature ranges from 600 ℃ to 800 ℃. It is found that the larger the temperature gradient, the more the transgranular cracks form due to the water-cooling shocks. A large number of transgranular and intergranular cracks cause the failure modes of rock samples under uniaxial compression to change from tension-shear failure to shear dominant failure accompanied by a large amount of powdery debris.

The calcareous sand particles have irregular shapes and are interlocked, which has a greater impact on the transmission of earth pressure. This paper carried out a model test on the dynamic response of earth pressure of the calcareous sand foundation with different degrees of compaction under cyclic loading, and revealed the response characteristics and attenuation law of the earth pressure of the calcareous sand foundation under the cyclic loading. The test results show that the dynamic response of earth pressure at each point near the end under cyclic loading is obvious. As the embedment depth increases, the peak earth pressure at each point decreases exponentially. The farther the horizontal distance from the central axis, the smaller the impact from dynamic response. The attenuation of earth pressure at 4 times of the load width below the square load surface is attenuated, and the vibration frequency has a certain effect on the peak earth pressure at the near end, but the effect on the far end is not obvious, and the relative densities of soil 50 cm away from the load center before and after loading show small variation. After increasing the relative density of sample, the soil particles are tightly interlocked, reducing the relative movement during loading, and increasing the impact depth of cyclic loading.

In view of two modes of general shear failure and composite failure of reinforced foundation, a new solution to the ultimate bearing capacity of strip footings resting on reinforced foundations near slope was derived based on the unified strength theory and the application procedures were given. Effects of the intermediate principal stress, the vertical spacing between reinforcement layers, the number of reinforcement layers, and the tensile strength of reinforcements were comprehensively taken into consideration in the new solution. Compared with other methods, the effectiveness and parameter influence characteristics of the proposed method were discussed. The results showed that the obtained solution to the ultimate bearing capacity of reinforced foundation agreed well with the results of model tests reported in the literature, and it had wide applicability. With the increase of the effect of intermediate principal stress, the ultimate bearing capacity of reinforced foundation near slope subjected to general shear failure and composite failure increased markedly. As the vertical spacing between reinforcement layers increased, the ultimate bearing capacity of reinforced foundation near slope increased first and then decreased under the general shear failure, but it would gradually reduce under the composite failure. The influence of the number of reinforced layers under the general shear failure can be divided into three stages, and that under the composite failure can be divided into two stages. Meanwhile, the effect of the tensile strength of reinforcements cannot be ignored. The research results can provide useful references for the optimization design of reinforced foundation near slope.

High temperature can cause the thermal fracture of rock, which affects the permeability of rock. In order to investigate the effect of temperature on the microstructure and permeability of rock, the ultrasonic velocity, density and gas permeability of granite after thermal treatment at 50–800 ℃ were measured. With the aid of CT scanning technique, the microstructure of granite was extracted and reconstructed. The influence of variation of microstructure after thermal treatment on permeability was also discussed in detail. According to this, the applicability of the K-C model and its improved model at high temperatures was discussed and verified. Finally, combined with the pore fractal model, a temperature-permeability model of granite after thermal treatment was proposed. The results show that: 1) The change of the internal microstructure of granite can be observed obviously as temperature increases. Uneven thermal expansibility of minerals before 400 ℃ can contribute to generation of many small pores between rock particles, which constitutes the pore structure. As temperature increases, these pores expand rapidly and connect with each other, forming the pore-fracture network. 2) When the temperature of heat treatment is not higher than 600 ℃, the probability distribution curve of the shape factor of the internal granite microstructure is basically consistent. When the temperature is higher than 600 ℃, the peak value of the shape factor shifts to the left obviously, and the average shape factor decreases greatly. 3) In the stage of pores, the permeability of granite doesn’t change too much, which is around the value of 10?18 m2. In the stage of the pore-fracture network, the permeability of granite increases exponentially with the connection of fracture. The permeability of granite under 800 ℃ is 8×104 times of the normal atmospheric temperature condition. 4) According to the fitting results of porosity and permeability at 50–800 ℃ using four porosity-permeability models, Bayles model and Costa model are more reasonable to describe granite after thermal treatment, and the fitting results are higher than K-C model and S-R model. 5) When the temperature is lower than 600 ℃, there is basically no change in the shape of the internal microstructure of the granite, and the shape coefficient of K-C can be considered as a constant. This indicates that Bayles model and Costa model are applicable for granite when the temperature is lower than 600 ℃. 6) On the basis of Costa model, the temperature-permeability model of granite after thermal treatment is obtained by combining the pore fractal characteristic of high-temperature heated granite. The experimental data within the temperature range of 50–600 ℃ are used to verify the new model and the coefficient of determination of fitting result reaches 0.99.

Phylite is widely distributed in southwest of China. Factors such as groundwater, bedding, micro-pores and micro-cracks will weaken its mechanical properties to some extent, thus posing severe challenges to the stability of the related projects. Therefore, in this paper, based on Brazilian splitting test, the evolutions of the tensile strength, energy and failure forms of phyllite under the coupling effects of water, bedding and pore are studied. The results show that the tensile strength decreases gradually with the increase of moisture content, pore diameter and bedding angle. However, the tensile strength has different sensitivities to the changes of them, which is mainly reflected in that bedding angle is the most significant, pore diameter is the second, and moisture content is the least. The tensile strength shows obvious anisotropy under different beddings. The anisotropy of tensile strength increases with the increase of water content and pore diameter, and the rate of increase with water content is more significant. Moreover, the energy increases gradually with the increase of moisture content, pore diameter and bedding angle, which is consistent with the changes of tensile strength. Although the energy under different beddings also presents obvious anisotropy, its anisotropy degree is generally higher than that of the tensile strength under the same condition. The failure form of specimens is affected by pore size, bedding angle and moisture content, among which, the existence of hole mainly affects the crack initiation position, the size of pore mainly affects the crack initiation strength, the bedding angle mainly affects the crack propagation path, and the moisture content mainly affects the number of cracks. This research results are valuable for further understanding the tensile properties of rocks and improving the stability of geotechnical engineering.

Since the layered soilbags is a congeries of individual soilbags, the discontinuous surface between the soilbags has the effect to reduce and absorb the vibration energy when it is used as foundation for low-rise building. However, the dynamic behaviour between soilbag interface was rarely studied so far. Using the large-scale direct shearing apparatus, the cyclic shearing tests were conducted on the soilbag interface and pure natural sand, and the variations of the shear stress, vertical displacement, dynamic shear stiffness, and equivalent damping ratio with shear displacement were compared. In addition, the interfacial frictional behaviour between the upper and lower soilbags was discussed. The results show that the initial shear stiffness, peak shear stress, and strain softening behaviour for soilbag interface are reduced compared to those of pure natural sand, but the shear stress-displacement loop is larger. The skeleton curve of soilbag interface can be better described using the Kondner-Zelasko model. For soilbag interface, an obvious contractive deformation is observed during cyclic shearing, while the dilatation is only observed under the low vertical stress and large shear displacement. The total contraction increases with increasing vertical stress, cyclic number and shear amplitude, and the change of vertical displacement within each cycle is smaller than that of pure natural sand. Additionally, the dynamic shear stiffness of soilbag interface is smaller than pure nature sand, but the equivalent damping ratio becomes larger, which indicates the advantage of soilbag structures to reduce vibration.

Typhoon rainstorms occur frequently in the southeastern coastal areas of China. The infiltration of rainwater under typhoon rainstorm conditions is an important cause of landslides in hilly mountains. Therefore, it is of great significance to study the migration law of rainwater infiltration wetting front under different geological environmental conditions. The temporal and spatial changes of rainfall infiltration were analyzed based on the monitoring data collected by the in-situ test of a landslide. A comprehensive rainfall infiltration model was established, which takes into account the nonuniform distribution of the initial water content of the soil and the slope environment. Then this model was verified by comparing to field test results and the predictions from existing classic models. The results demonstrate that: 1) At the initial stage of rainfall infiltration, the increasing slope of water content at different depths was steep. With the increase of time, the slope gradually slowed down. When the accumulated amount of rainfall reached 44.4 mm or more, the shape of the water profile changed from "Z" to reverse "S". As the rainfall intensity decreased, the type of rainwater infiltration process changed from water infiltration to non-water infiltration. At the later stage of infiltration, the growth rate of water content at different depths tended to be constant, and a stable infiltration stage was reached. 2) The migration speed of the wetting front increased with increasing rainfall. At the beginning of the rainfall, the rainwater infiltration rate was large. The migration speed of the wetting front was fast, and it decreased with the increase of soil depth. 3) The results of wetting front depth change over time calculated based on the improved rainfall infiltration model are consistent with the field monitoring test results, indicating that taking into account the slope angle and the inhomogeneity of the initial water content distribution can improve the accuracy of the predictions of the Green-Ampt model. The research results can have a certain significance for establishing an effective early warning model for landslides induced by the typhoon rainstorm.

An indoor permeability test was conducted to study the sealing performance of joints between the compacted blocks which were backfilled with bentonite powder (P), bentonite particle-powder mixture (P/P) and bentonite slurry (S), respectively. The swelling stress and hydraulic conductivity were monitored during the permeability test. After the test, the homogenization of blocks and sealing degree of joints were evaluated according to the X-CT scanning test, thermal conductivity test and microstructure test. The results show that: with the increase of hydration time, the bentonite in the core area of the block intrudes into the pores of the joint, and the increase rate of swelling stress in the joint zone is higher than that in the axial direction of the block, which leads to the slowing down of the development speed of the axial swelling stress of the block and produces hysteresis. The joint sealing materials have significant influence on the hydration process of the block system, resulting different swelling stress development rates. The sealing degree of the joint is positively correlated with the initial dry density of the joint filling material. The X-CT scanning images show that the sealing joint and the block have been "welded" together after hydration. By contrast, there is still a gap between the blocks with a blank joint, showing a lower sealing degree. The MIP and SEM tests demonstrate that the pore size distribution of inter-aggregates in the joint area lies in the proportion between 3 μm and 30 μm, and a certain number of large pores with a diameter between 100 μm and 500 μm were observed in the joints sealed with bentonite slurry. Some fissure-like 2-dimensional pores appeared in the blank joint according to the SEM picture. Generally, sealing can significantly improve the expansion ability and homogeneity of the block system, and the impermeability and thermal conductivity of the healing block system are close to that of the intact sample. Joint backfilled with bentonite particle-powder mixture shows a better sealing performance, followed by the joint sealed with bentonite powder and bentonite slurry, and the sealing effect of joint without backfilling is the worst.

Estimation of geometrical and hydraulic properties of rock fracture networks is of great significance for underground engineering construction and environment safety. Flow tests were conducted for 3D printed fracture network specimens in this study, in which each fracture had different orientations, lengths, rough surfaces and heterogeneous apertures. A numerical procedure was developed to simulate the fluid flow through the fracture network with the same geometrical properties as the specimen. Effects of surface roughness, aperture, hydraulic gradient and flow direction on the fluid flow through fracture networks were systematically investigated. Results show that as the flow rate increases, the relationship between the pressure gradient and the flux through the fracture network transits from a linear relationship to a nonlinear one, and the nonlinear relationship can be well fitted by Forchheimer’s law. The critical hydraulic gradient in different flow directions ranges from 0.015 to 0.195. The ratio of the pressure drop induced by the inertia force to the total pressure drop increases with the increasing hydraulic gradient, while the rate of increase gradually decreases. When the hydraulic gradient is close to 1.0, the pressure drop induced by the inertial force accounts for 68.5% of the total pressure drop. The topology of the fracture network determines the overall connectivity of the model, and the heterogeneous aperture allows the fluid to preferentially flow through the channels with greater permeability and smaller resistance within the connected fractures. Therefore, the ratio of areas of the main flow channels to the total area of fracture planes is smaller than 41%. The permeability of fracture networks decreases with the increase of the surface roughness of the fracture, but the decrement is reduced by increasing the fracture aperture. This study provides reliable laboratorial and numerical methods to analyze flow properties through rough fracture networks.

In order to study the influence of joint density on the strength characteristics and failure modes of rock mass, the rock-like specimens with different joint densities were prepared by using 3D sand printing, with the quartz sand and furan resin being employed as the printing materials. The uniaxial compression test was performed on the 3D sand printed specimens, and the digital image correlation (DIC) method was used as a non-contact technique to monitor the full-field deformation. The crack initiation, propagation and coalescence behaviors were quantitatively analyzed from the micromechanics point of view. The results show that the shape of stress-strain curve and the compressive-to-tensile strength ratio of 3D sand printed intact specimen are similar with those of the natural rock, which can be grouped as a rock-like material. The variation processes of stress-strain curves with different joint densities are similar, and can be divided into initial compaction, linear elastic deformation, crack development and residual strength stages. The mechanical properties of specimens decrease with the increase of joint density ?f, and the relationship can be expressed as exponential decay functions. By calculating the strain field and displacement vector distribution on the specimen surface, the deformation field distribution and crack propagation of the specimen are found to be closely related to the joint density. The failure mode shifts from axial tension failure (?f = 0.280%) toward mixed failure (?f = 1.193%) and then to tensile coalescence band failure (?f ≥ 1.712%) as the flaw density increases. When the joint density is greater than or equal to 2.739%, the block rotation appears in the tensile coalescence band, and the bookshelf faulting with block rotation is reproduced.

In order to investigate the anchoring effects of the bolts on the jointed rock mass and its influences on crack propagation, the unanchored and anchored rock-like specimens with joint angles of 15o, 30o, 45o, 60o, 75o and 90o were made. The MTS816 was used for uniaxial compression test, and the acoustic emission (AE) and digital image correlation technology (DIC) were used to monitor the crack growth. In addition, the particle flow code software PFC3D was used to study effects of different anchoring angles on crack propagation. The results show that the peak strength, peak strain and cracking stress of the anchorage unit are improved compared with the unanchored specimens. The existence of bolt reduces the stress intensity factor during the crack initiation and propagation of the tensile wings, which can limit the initiation and propagation of tensile cracks effectively. Moreover, the occurrence of shear cracks can be inhibited. The process of the tensile crack propagation can be divided into initial stage and acceleration stage. The displacement of the characteristic points of the specimens with bolts is smaller than specimens without bolts. According to the PFC3D simulation results, the anchoring effect is the most obvious when the anchoring angle ? is 45o. With the increase of the anchoring angle ?, the development degree of the tensile wing crack first increases and then decreases. The failure mode of the prefabricated fracture specimen changes from shear failure to tensile-shear compound failure, and then to shear failure. The results can provide a reference value for analyzing the stability of rock engineering.

The uniaxial compression and uniaxial cyclic loading and unloading tests were carried out on sandstone, and the variation laws of residual deformation, deformation modulus and lateral expansion coefficient under cyclic loading were obtained. In addition, the evolution laws of the rock input energy, elastic energy, dissipation energy, damping energy, damage energy and other energy indicators were determined. The normalized damage energy was used to characterize the damage evolution of the rock and analyze the failure modes from the macro and micro perspectives. Studies have shown that: under cyclic loading and unloading, the residual deformation exhibits a trend of deceleration-stabilization-acceleration increase. The deformation modulus of sandstone first increases and then decreases, and the lateral expansion coefficient is basically positively correlated with the number of cycles. The input energy, damage energy and the proportion of damage energy to the dissipation energy have the U-shaped distribution. Moreover, a decrease is first observed in the damping energy followed by an increase, and the proportion of damping energy to dissipation energy has the inverted U-shaped distribution. Additionally, the elastic energy generally grows slowly, and the proportion of elastic energy to input energy has the inverted U-shaped distribution. The damping energy increases with the increase of stress ratio, while the proportion of damping energy decreases. The damage of sandstone develops in three stages: deceleration-stabilization-acceleration. The compound failure mode combining shear failure and tension failure in the conjugate inclined plane is generally found in the sandstone, and the failure transforms from unstable damage to failure damage.

With the increasing size of open caisson foundation in large bridge project in China, the overall settlement of large open caisson foundation is vital to the shape control of high-speed railway bridge. In this paper, by taking the open caisson foundation of long-span and rail-cum-road Changtai Yangtze River Bridge as the engineering background, the overall settlement of the sinking well foundation during the Changtai Yangtze River Bridge construction stage is comprehensively analyzed. In addition, based on the distribution of the stratum and the size of open caisson foundation, the corresponding centrifuge model tests are conducted. According the results of tests, it can be seen that the overall settlement of open caisson foundation can be divided into three stages: slow growth, sharp deformation and leveling off. In addition, the overall settlement calculated by the layered sum method with actual compression modulus of the soil is in good agreement with that of the centrifugal model test and the overall settlement of the open caisson foundation is about 220 mm when the construction stage is finished. This study provides an important reference for the design of open caisson foundation of Changtai Yangtze River Bridge and has referential value to similar open caisson foundation engineering.

The mining of metal mines by sublevel caving often results in excessive surface deformation and damage to the buildings on the ground. Scholars mostly study the boundary of the acceptable deformation (movement curve) and the angle of the boundary of the acceptable deformation on the surface of the metal mine. The curve is the boundary of area where normal living or use is not ensured due to damage of surface buildings or structures, but the area outside of the line is still affected, which is lack of studies on it. Therefore, studying mining influence range and limit angle is of great significance to mining theory. Taking the west area of Chengchao Iron Mine in Ezhou, Hubei as an example, based on the results of monitoring data of horizontal surface displacement in the past 4 years (from May 2016 to May 2020), measuring error is taken into account and the threshold value is set. The influence curve can be obtained through Kriging interpolation, and the limit angle is determined. Comparing with the movement curve and moving angle, the results show that there is a sudden change in the range of the influence curve of the hanging wall, and the mining level plays a dominant role in the extension of the influence curve. The influence curve can be a warning sign of the extension of the boundary of the dangerous deformation zone. A large structural crack will cause a wide range of influence curve in local footwall area, the limit angle outside the structural crack has the same change pattern as the movement angle. The difference in the mining boundary of different levels has an important impact on the limit angle in the hanging wall, which indicates that the boundary difference effect of the upper and lower layers should be considered when studying the limit angle and deformation prediction caused by metal mining. The stability of the limit angle depends on whether the mining level has major changes. Due to the existence of the pillar, the limit angle in the end area is about 6o smaller than the movement angle.

Fast, efficient and accurate 3D geological model construction is the key to expand the application of 3D geological model in engineering. There have been many methods proposed to build a boundary representation 3D geological model quickly and automatically. However, present methods cannot accurately identify the interlayers and lenses, which leads to an error of mesh illegal intersection on the side boundary of the model. To solve this problem, a method of side boundary reconstruction that building the model overall firstly and making partial adjustments secondly to avoid illegal mesh intersection on the side boundary of the model is proposed based on the rapid mesh intersection algorithm of the geological model with 4 steps. Firstly, construct the upper and lower surface model of each stratum based on the boreholes data. Secondly, build the side boundary surface based on the stratum sequence. Thirdly, classify the stratum blocks into ordinary stratum and interlayer, and obtain the intersection polygons of the triangle mesh on the side boundary of the interlayer and its intersected meshes on the ordinary stratum through the mesh intersection algorithm. Finally, realize the reconstruction of the side boundary of the model with triangulating the intersection polygons and updating to the mesh list of strata. Apply this method to the modeling on a certain area, and the results show that the method is capable of quick and highly automatic reconstruction of the side boundary with the existence of interlayers and lenses.

Based on the complex cone optimization technique, a lower bound finite element limit analysis method based on the generalized Hoek-Brown yield criterion is proposed in this paper. The generalized Hoek-Brown yield criterion has some problems including the numerical singularity at the edges and sharp points in the principal stress space. The generalized Hoek-Brown yield criterion used in the finite element limit analysis method generally needs to be approximated. How to deal with the yield criterion accurately and effectively is always a difficult problem in the finite element limit analysis method. To solve this problem, using the cone optimization technique, including power cone programming (PCP) and semidefinite programming (SDP), the yield function can be directly transformed into the complex cone optimization model. The application of complex cone optimization can avoid the approximate treatment of yield criterion. In addition, a strict lower bound solution can be obtained by treating the yield criterion with the proposed method. In order to improve the calculation accuracy of the proposed method, an adaptive mesh refinement strategy based on the node stress of the element is introduced. On the basis of the existing research, the corresponding adaptive lower bound limit analysis finite element program is compiled. The results show that the proposed method can yield the lower bound solution with high accuracy, and indirectly reflect the failure mechanism of the structure.

Land subsidence has been one of the main geological disasters with great harm. Full section monitoring of land subsidence borehole using distributed fiber optic sensing (DFOS) techniques has been proved to be an effective method. The deformation compatibility between cable and soil is a key factor which matters the land subsidence monitoring effectiveness. Using the discrete element numerical simulation software MatDEM, a 2D discrete element cable pull-out test model was established to explore the deformation compatibility between cable and the surrounding soil during pull-out under different confining pressures. The results show that the 2D discrete element cable pull-out tests model can accurately reflect the distribution of axial strain along cable and the displacement of soil element during the pull-out. The curves of pull-out force versus pull-out displacement and the distribution of axial strain along cable under different confining pressures show a progressive failure mode. Based on the slip depth of cable obtained by the discrete element method, the coefficient of cable-soil deformation compatibility is corrected. Moreover, the monitoring data of land subsidence in Shengze, Suzhou, was taken as an example to analyze the cable-soil deformation compatibility under different confining pressures and pull-out displacement conditions. The critical confining pressure is about 0.19 MPa and the critical depth is about 17 m in this region. The results verify the feasibility of the discrete element numerical simulation method in exploring the cable-soil deformation compatibility, and further demonstrate the reliability of DFOS in land subsidence monitoring.

The fiber Bragg grating (FBG) sensor is an important tool to measure the surface strain of geogrid. There is a strain transfer coefficient between the real strain of geogrid and the strain measured by FBG sensor due to the existence of adhesive layer. In this study, by taking surface-bonded bare fiber Bragg grating as the research object, the strain transfer formula between fiber layer and matrix layer is derived by establishing the theoretical model of fiber layer, adhesive layer and matrix layer. In addition, the effects of material parameters on the strain transfer coefficient and the average strain transfer coefficient are analyzed. Then, through laboratory tensile test and verification test, the correctness of this newly proposed theory for strain transfer is verified. The results show that the maximum error between the measured value and the theoretical value is about 15%. According to the parameter analysis, the influence of different material parameters on the average strain transfer coefficient can be arranged in a descending order as follows: the FBG bond length, the thickness of the adhesive layer, the shear modulus of the matrix layer, the width of adhesive layer and the shear modulus of adhesive layer, accounting for 33%, 23%, 20%, 13% and 11% respectively.