Suction is a focus of unsaturated soil research and investigation on suction is challenging. Many physical phenomena in nature can be explained by suction, and the research challenge is that the quantitative measurement technology of unsaturated soil suction is immature. Unsaturated soil, as a three-phase composite material widely exists on the earth surface, has far more complicated mechanical properties than saturated soil. The main reason is that a curved liquid surface contraction film is formed at the water-air interface in the unsaturated soil, which causes the soil pores to produce suction. The strength and deformation characteristics of unsaturated soil are the macroscopic manifestations of its internal suction, and the microstructure serves as a bridge to connect macroscopic physical and mechanical properties with suction. It is an important way to improve soil mechanics to grasp the microstructure of unsaturated soil as well as the theory and experiment of suction. It is pointed out that the research on the dynamic structure evolution of unsaturated soil-liquid bridge and the distribution characteristics of suction force chain is an important basis to fully understand the mechanical properties of unsaturated soil, and it is also an important means to grasp and quantify the suction of unsaturated soil.

Rain infiltration through the soil is the critical factor in the frequent landslides on the coast of China. By considering the geological disaster points of Dehua County, Quanzhou City, Fujian Province as the main research object, the permeability characteristics of slope soil and granite residual soil are concerned in these typical geological disaster points. The one-dimensional soil column infiltration test was carried out using the soil infiltration device developed by simulating rain intensities of 15, 30 and 60 mm/h, respectively, with the rainfall conditions of duration (180 min) and amount (90 mm). The response law of moisture content, wetting front and infiltration rate of each soil column with time under different working conditions was investigated. The main results are presented in detail. The soil wetness spreads deeper and faster as the permeability coefficient of soil and the rainfall intensity become greater. The soil moisture content responds to rainfall from shallow to deep part during the process of rainfall infiltration. Meanwhile, the influence of different rain intensities on water content is mainly reflected in the first response time and saturation time. The high intensity of rain leads to short response time and a quick saturation speed. A function is proposed for different rainfall intensities, which can characterise the wetting front infiltration laws of the Maping landslide and the Bengtuling landslide in Dehua County. The results are of great significance for the early warning of landslide hazards.

To study the influence of underground space structure on ground motion, a shaking table test of soil-underground structure dynamic interaction was designed and carried out with a three-story underground shopping mall structure as a prototype. Six seismic waves with different predominant frequencies and peak accelerations were regarded as input waves to test ground motion. The experimental results show that the amplification factor of horizontal acceleration of ground surface is symmetrically distributed along the axis of the underground structure. The underground structure significantly affects the horizontal acceleration of the ground surface above and adjacent to the sites. At the same time, due to the local site effect of underground space structure, vertical vibration will occur even under horizontal seismic excitations. The amplification factor of vertical acceleration of ground surface is distributed as M-shaped. The influence range of underground space structure can reach a distance equal to its own width on both sides. The amplification factor of acceleration of ground surface is obviously affected by the predominant frequency of input seismic wave, and decreases with the increase of peak ground acceleration (PGA), but the space amplification factor increases with the increase of PGA. The peak frequency of ground acceleration Fourier spectrum is influenced by the predominant frequency of seismic waves, natural frequencies in horizontal and vertical directions of soil site.

Sludge is rich in organic matter, which would generate humic acid after decomposition. Humic acid will affect the reaction process and strength of cement-treated soil. The unconfined compressive strength (UCS) of sludge treated with 12% cement may decrease after 60 days curing. If adding both of lime (3%) and cement (12%) into sludge, the pH value of treated soils is higher than 10.5 after 180 days curing, and the UCS increases from 750 kPa (cured 28 d) to 1 500 kPa (cured 120 d), which indicates that lime can improve the UCS of treated sludge significantly through establishing suitable strong alkaline environment. However, the UCS of treated sludge reduces to 1 250 kPa after 180 days curing, which may ascribe to humic acid dissolving hydration products of lime and/or cement. The calcium ion concentration increases with the elapsing of curing period, which could explain the behavior of humic acid attacking to hydration products. Metakaolin contains lots of amorphous silicon and aluminum oxides, with the addition of 3% metakaolin into sludge based on mixing with lime (3%) and cement (12%), the UCS increases in the whole curing period (180 d). The results show that metakaolin can capture the calcium ion in short time and form stable cementitious materials in solidified soils. And these cementitious materials have strong anti-erosion capacity to humic acid effect. These above findings prove that metakaolin can improve the long-term performance of cement treated sludge.

The structure of unsaturated clays can significantly affect its mechanical properties. Based on the classical BBM (Barcelona basic model) and a hardening rule which can describe cyclic plasticity, an elastoplastic two-surface model is established to describe the static and dynamic mechanical properties of unsaturated structural clays under constant suction condition using the volumetric damage rate as the standard soil structural damage parameter. The proposed model includes a structural bounding surface and a loading surface which are geometrically similar to the yield surface of reconstituted unsaturated clays in the stress space. Based on the principle of radial mapping and movable memory center, the cyclic plastic characteristics and structural damage process of unsaturated structural clay under cyclic loading are reflected by the evolution of structural boundary and loading surface in stress space. By comparing with the relevant experimental results of unsaturated clays under controlled suction, it is shown that the model can well reflect the main mechanical behaviour of unsaturated structural clays under static loading, and the stress-strain behaviour predicted by the model under cyclic loading is also reasonable.

The frost heave force is one of the main reasons that induces the tunnel freezing damage. The frost heave force of tunnel is mainly caused by the differential frost heave of surrounding rock. The fracture will further affect the differential frost heave of rock mass. In this article, the calculation formulation for differential frost heave coefficient of rock mass is derived, and some findings concerning the coefficient of differential frost heave are drawn as follows. The differential frost heave coefficient increases with increasing the angle ? between fracture and temperature gradient. As temperature gradient rises, the differential frost heave coefficient increases. The influence of fracture ratio on differential frost heave of surrounding rock depends on the angle ? between fracture and temperature gradient. When ? is small, decreases with the increase of fracture ratio. When ? is large, increases with the increase of fracture ratio. The influence of fracture on differential frost heave of rock mass is related to the lithology of rock mass. The fracture has greater influence on the rock mass with smaller porosity. According to the calculation formula of differential frost heave coefficient of fissured rock mass, the range of differential frost heave coefficient of fissured rock mass with different lithology and different grades can be obtained. Therefore, in the design of tunnel in cold area, the frost heave force of tunnel surrounding rock acting on lining can be calculated more accurately, which plays an important role in the design of tunnel in cold area, and also promotes studies of the frost heave force of subgrade, slope and other projects in cold area.

To investigate the effect of loading rate on tensile strength of rock materials and morphologies of fracture joint surfaces, Brazilian disc tests were conducted on three rock samples (i.e., granite, basalt and limestone) under different loading rates. The tensile strength was determined and the effect of loading rate on tensile strength was presented in detail. Three-dimensional (3D) scanning technique was employed to establish the digital terrain of fracture joint surface, and the effect of loading rate on fracture morphology of fracture surface was studied qualitatively. The relationships between surface roughness and loading rate and tensile strength were further analyzed by calculating the roughness index of fracture joint surface of three kinds of rock. The results show that tensile strength increases with the increase of loading rate, and under the double logarithmic coordinate system, it shows a good linear correlation between the parameters. According to the morphology of the fracture joint surface of rock materials, and from the perspective of the roughness of combination of qualitative and quantitative evaluation, it is found that the loading rate and tensile strength have a significant influence on the roughness of the fracture joint surface. The higher the loading rate is, the greater the tensile strength is, and the roughness of the fracture joint surface is. This study provides some reference for a better understanding of the relationship between the morphology index and mechanical parameters of the joint surface.

The uniaxial step loading and unloading creep experiments were conducted on the sandstone samples from Shaanxi Province to analyse the law of energy evolution of the samples during the process of deformation and failure. The results show that with the increase of cyclic series, the dissipation energy of each grade exhibits a nonlinear increase and the plastic strain energy of each grade is relatively stable. The dissipation energy exceeding plastic strain energy can be regarded as a precursor energy characteristic of the sample failure. By defining the correlation coefficient and establishing the relationship between energy and deformation, it can be found that with increasing cyclic series, there is a positive correlation between the plastic strain energy and the new adding plastic strain of each grade, and the dissipation energy of each grade is positively correlated with the plastic strain accumulation. According to the calculation of the energy of loading, creep, unloading and recovery stages, the evolution rate of energy in each grade increases with the increase of cyclic series. When the rates of loading and unloading are constant, the change rate of energy at the loading stage is larger than that at the unloading stage, and the change rate of energy at the creep stage is greater than that at the recovery stage under the same grade. Finally, by analysing the change law of energy at each cyclic loading stage, an energy attenuation coefficient is proposed, which decreases as a power function with increasing stress level. Thus, an effective method is introduced for predicting failure stress.

In this paper, a large-scale physical model test of landslide prevention and control was conducted to investigate the deformation and displacement of the lattice anchor system in soil landslide under the surcharged load on the top of the slope. The objectives revealed the anti-sliding mechanism of lattice anchor. The relationship between the anchorage force and slope displacement and anchor deformation was discussed, and a calculation method of the ultimate anchorage force was proposed. The results showed that when the landslide was initiated, the lattice beam and the slope as a whole-body rotate and slip, the bolts are bent and deformed at the slip surface, which was in a state of bending and tensile stress. The anti-sliding is implemented by the shear resistance of anchors near the sliding surface and by the retaining resistance of the lattice beam with anchors. The ultimate anchorage force of the lattice anchor consists of three parts: initial pre-stress of the bolt, anchor tension caused by bending deformation of the bolt and anchor tension caused by the slope displacement. It can be calculated by the formula: . The results can provide some reference for the optimal design of the lattice anchor system.

This paper is to measure the soil-water retention curves (SWRC) of undisturbed and compacted soil specimens and compare the differences in measured data between these two soils. The mercury intrusion porosimetry (MIP) tests are conducted to explore the difference in the pore size distributions (PSD) between the undisturbed and compacted specimens and investigate the evolution law of PSD during drying. By considering shrinkage during drying, the basic parameters of SWRC can be determined based on the PSD. The results show that the undisturbed specimens in the wide suction range exhibit a unimodal PSD. The saturated compacted-specimen exhibits a unimodal PSD, but becomes the bimodal structure obviously during further drying. The SWRC of undisturbed specimens has a typical shape of “S”, but the compacted specimens have a “horizontal stage” in the transition zone. The pore diameters governing the air entry value and residual value can be determined by the PSD of MIP tests, and then corresponding suctions can be calculated, which are consistent with the physical meaning.

Temperature is an important factor that affects properties of oil contaminated soil. This study considered the special characteristics of the climate environment in the coastal area and used unconfined compressive strength and stress-strain distribution to optimize the requirement for two kinds of ash solidified materials, and the temperature sensitivity was used as an evaluation criterion. Results indicate that the compressive strength of the oil contaminated soil significantly fluctuates, and it is up to two times in the temperature range of -20?40 °C. However, the fluctuation reduces to 10%?20% after soil solidification with two kinds of ash. Solidified materials can adsorb and enclose the temperature sensitive substances (oil, water and salt) in the gel body and even outside, and then it can enhance the resistance to the variation of environmental temperature. The unconfined compressive strengths of oil contaminated soil and solidified soil decrease first and then increase with the increasing of temperature, and 10 °C is the turning point, which is the lowest point. The results suggest that this temperature should be of particular concern in practical engineering. Under the action of temperature, the failure mode of solidified oil contaminated soil is strain-softening. With the increase of temperature and the contaminated level, the plastic deformation stage is prolonged, and the axial strain gradually increases. Finally, the surrounding layered damage occurs. The contaminated level of soil itself affects the solidified effect, and the fluctuation of compressive strength under a high level of contamination is about 40%. Therefore, in actual engineering, the solidified requirement should be adjusted according to the contaminated level. As to the soil with low contamination, the solidified requirement is only slightly higher than that of the uncontaminated soil, and too much solidification for the soil with low contamination is often counterproductive. Lime has more contribution than fly ash to soil stability under the same additive to soil ratio. As to the oil-contaminated saline soil with 6% contamination, the optional solidified condition is 10% lime +20% fly ash.

In order to explore the failure mechanism of rocks under linear cutting with single cutter, a large-scale model test platform was used to carry out linear cutting tests on sandstone. This study employed the fractal geometry method to analyze the geometric characteristics of cutting products, including cutting grooves and cutting fragments, at different cutting angles and different cutting depths. The experimental results show that the cutting width has a good linear relationship with the cutting depth, and increases with the increase of the cutting depth. The cutting width corresponding to the same cutting depth is the smallest when the cutting angle is 45 degrees. The fragment-size distribution of sandstone has fractal characteristics and the fractal dimension is concentrated in the range of 1.88?2.66. The fractal dimension has a good linear relationship with cutting depth and decreases with the increase of cutting depth. The relationship between fractal dimension and cutting angle can be fitted by quadratic function, but the coefficient of quadratic term of the fitted function changes from positive value to negative value with the increase of cutting depth.

Chemical electroosmosis method is one of the fast and effective methods for soft ground treatment, which is widely accepted by engineers. In order to study the effect of reagent injection mixing ratio on chemical electroosmosis treatment of soft clay, model tests on electroosmotic were carried out, and the CaCl2 and Na2SiO3 solutions were combined to study the injection effect. The electroosmotic drainage effect was obtained when the ratio of the concentration of the substances was 1:1, 1:2, 1:3, 2:1 and 3:1 respectively. The displacement, drainage rate and drainage microscopic characteristics of each working condition after the test (ICP-MS), energy consumption, drainage effect, reinforcement effects, and uniformity were also discussed. The results show that when the concentration ratio of CaCl2 solution and Na2SiO3 solution was 1:1, the chemical electroosmosis effect is the best, the anodic corrosion amount is the least, and the energy consumption is the lowest. The electroosmotic effect is mainly influenced by the reagent injection ratio, specifically, by the type and quantity of cations added to the reagent, and the effect of Ca2+ on chemical electroosmosis is relatively prominent.

The phenomena of incompatible deformation are observed in the block rock mass on dynamic propagation between blocks and block partings composed of the weak medium. The dynamic incompatible deformation influences the stability of the block rock mass. At present, the studies of characteristics response of block rock mass incompatible deformation are limited, which induced the difficulty to recognize this dynamic phenomenon. In this paper, the characteristics of the incompatible dynamic response of block rock are studied through experiments. The incompatible deformation characteristics of block rock mass are analysed. The velocity of dynamic propagation, attenuation of block acceleration amplitude, displacement of block rock vibration, duration time of block vibration and kinetic energy of the block, the frequency response of blocks are analyzed on the dynamic propagation in the block rock mass. Compared with the longitudinal wave, incompatible deformation dynamic propagation in the block rock mass is low-frequency and slow-velocity wave. When block rock mass has incompatible deformation, the vibration displacement of block rock and vibration duration time are increased. In this process, it contains conversion between kinetic energy and potential energy. These phenomena are critical characteristics to recognize the incompatible deformation dynamic propagation. This study provides the reference for the recognition of incompatible dynamic propagation in the block rock mass and wave warning of block rock mass on impact response.

In order to study the humidification and deformation characteristics of intact loess under complex stress conditions, the double-line grading wetting tests on intact loess under measuring suction were carried out by using collapsing true triaxial apparatus for unsaturated soil. The variation characteristics of suction under the action of coupling stress and water were discussed. The humidification deformation characteristics of true triaxial soaking tests and the effects of suction, net confining pressure, intermediate principal stress and stress ratio on humidification deformation were studied. The results showed that the yield points of unsaturated soil were determined by the ei-lgp compression curves. Before the yield points, the slope of the curves were approximately equal. After the yield points, the slope reduced with the decrease of the initial suction, and the intersection points between unsaturated soil and saturated soil moved to the lower right with the increase of initial suction. In the process of isotropic compression, suction approximately linearly decreased with the increase of net average stress, the smaller the initial suction, the slower the suction decreased and the smaller the variation amount of suction. When grading soaking and humidifying under pressure equalization, suction s decreased with the increase of water immersion w, and the humidification volume strain enlarged with the increase of water immersion w. The -w relationship curves under different net confining pressures intersected with each other. Before the intersection area, the larger the net confining pressure, the smaller the humidification volume strain, and after the intersection area, the larger the net confining pressure, the larger the humidification volume strain. Under the same net confining pressure condition, when the water immersion amount was the same, the larger the initial suction, the larger the humidification volume strain. In the true triaxial shear humidification tests, the stress ratio k, the intermediate principal stress parameter b value and the net confining pressure ?3 all had a certain influence on the humidification deformation. When q/p≤1, the front section of the humidification deformation curve was lower concave, and the back section was upper concave, mainly showing volume humidification deformation. When q/p>1, the humidification deformation curve had only the lower concave part, which was mainly characterized by shear humidification deformation. The shape of the humidification deformation curve depended on different combinations of k and b values.

In this study, semi-diagenetic rock specimens of the Xigeda Formation in Zhaizi village on Jinshajiang River were investigated. The mineral composition of the specimens was determined by X-ray diffraction (XRD), and the microstructure and change of mineral particles in natural and saturated states were observed by scanning electron microscopy (SEM). The influences of water and confining pressure on the strength and deformation of semi-diagenetic rock of Xigeda Formation were determined using triaxial compression test. And the microcosmic mechanism was also discussed. The strength characteristics of the semi-diagenetic rocks of Xigeda Formation different from that of the soil and the soft rock were revealed by statistical analysis of the relationship between the strength indexes and water content of rock, soil and soft rock. On the basis, engineering classification suggestions for the semi-diagenetic rocks of Xigeda Formation were given. Based on the above research, some conclusions are as follows. 1) The microstructure shows that the semi-diagenetic rock of Xigeda formation has weak cementitious structure which is obviously different from that of soil and rock. The cementation structure is easy to be destroyed after saturation. 2) The cohesion and friction angle of semi-diagenetic rock decrease with the increase of water content. The average modulus increases with the increase of confining pressure at high water content, it decreases with the increase of moisture content when the confining pressure is constant. 3) The order of cohesion is soft rock> semi-diagenetic rock of Xigeda Formation>soil. The sensitivity of the cohesion to the water content is soft rock> semi-diagenetic rock of Xigeda Formation>soil. The sensitivity of the friction angle to the water content is soil > semi-diagenetic rock of Xigeda Formation> soft rock. 4) The rocks or soils should be classified as hard soil-soft rock, with the uniaxial compressive strength between 0.2 and 3 MPa, and cohesion between 30 and 200 kPa, measured from a standard specimen (Φ 50 mm×100 mm). It is suggested that it should be distinguished from rock and soil in practical engineering application.

The rock joint roughness has many characteristics like heterogeneity, anisotropy, nonuniformity and scale effect. In engineering practice, different statistical methods are utilized for analyzing the rock joint roughness due to its uncertainty. However, previous studies often neglected the impact of insufficient samples on statistical results. To solve the problem that reasonable number of samples cannot be determined during the statistical measurement of joint roughness, the methods based on the coefficient of class ratio analysis and the simple random sampling principle are proposed for determining the minimum number of samples (MNS), respectively. In the case study, the MNS of statistical measurements is determined based on the proposed methods. The results of rock joint samples are compared and analyzed with different sample sizes. The results indicate that the coefficient of variation (CV) value of the small samples is significantly larger than that of large ones, and the CV value decreases with the size of samples. The CV values of the joint samples with the sizes of 10?50 cm basically are in a range of 0.31?0.47, and the values for those of 60?100 cm samples are between 0.21?0.31. The relationship between MNS and sample size basically satisfies the power function relationship, and the MNS decreases with the sample size. The MNS determined by the former method with an allowable error of ±2% is consistent with that calculated by the latter with a maximum allowable error of 10% and a confidence level of 95%. The similarity of the results based on these two methods is greater than 0.997. This study can provide basis for quantitatively obtaining the MNS in rock joint roughness statistical measurement, and can ensure the accuracy of JRC statistical analysis. It is of great significance to accurately obtain mechanical parameters of rock joints in rock mass stability evaluation.

Studying the seismic effects of valley site has critical guiding significance for site selection and aseismic design. Based on the analysis of centrifuge shaking table tests, the ground motion response pattern of the trapezoidal valley was studied. The results showed that there was a certain amplification effect of ground motion in the bedrock valley site. The amplification effect varied with the change of terrain, but the amplification effect was not significant. Different site locations had a small influence on the response spectrum. In the bedrock-overburden model, an obvious increase of the ground motion magnification was observed at the bedrock surface. Different magnifications were found under different input ground motions. The amplification effect of the ground motion was particularly evident on different sites when the frequency band was in the range of 0.5?2.5 s. In this frequency band, the frequency range of ground motion amplification was increased significantly, which was different from the pure bedrock sites. In the case of the pure bedrock sites, although the shape of the response spectrum was somewhat different for individual sites, the plateau value and characteristic period of the response spectrum were similar. Due to the terrain effect of the valley site, the amplification factors of the peak surface acceleration of the valley site changed with the change of the terrain. The higher the terrace levels of the valley, the greater its magnification, and the amplification of valley bottom was the smallest. With the increase of the input ground motion intensity, the higher the terrace levels, the higher the plateau value, and the greater the characteristic period of the response spectrum.

The aim of this study is to quantitatively characterize the structural changes of effective seepage channels in water infusion coal body. The structure characteristics of the coal body under various confining pressures and water infusion pressures are measured via nuclear magnetic resonance (NMR) technology. The fractal characteristics of effective seepage channel in coal body are analyzed with fractal geometry theory. The results show that the coal body with water infusion has an intertwined internal fracture-pore structure and that the pore radius distribution is diverse under the influence of different water pressures and confining pressures. The variation of large pores volume is 13.72%, followed by transitional pores and medium pores of 8.12% and 5.39%, respectively. The smallest micro pores is 2.05%. Combined with the T2C test results, when the pore radius is greater than 270 nm, it is an effective seepage channel, and the pore structure affecting the seepage characteristics of the water infusion coal is mainly concentrated in the large pores and medium pores. In the process of test, the change of fractal dimension of test and theory is small, which shows that the structure of seepage passage of coal sample has obvious fractal characteristics under different pressure conditions. At the same time, the opposite change trend of the two verifies the different significance of their respective characterization.

A series of dynamic centrifuge model tests on clay tailings reservoir as well as the reservoir after expanding has been performed in a centrifuge shaker. The seismic behavior examined in this study includes the acceleration amplification, variations in the pore water pressure both in soft clay foundation and in clay tailing, deformation of the soft ground-clay tailing-tailings dam system. The experimental results indicate that the acceleration amplification by the soft clay ground is limited, while the acceleration response increases with height for the tailings dam. The strongest acceleration response occurs at the highest sub-dam, especially at the highest one of the tailings dam after expanding. There is an increase in pore water pressure induced by earthquake both in soft ground and in clay tailing, but no liquefaction occurs. The ground motion, soft foundation and the consolidation state of tailings in the reservoir have great influence on the deformation mode of tailings reservoir. If the soil is not sufficiently consolidated and the earthquake is strong enough, horizontal movement of the clay tailing and rise of soft clay in the downstream can occur. Seismic settlement can be found if the soil is sufficiently consolidated and the shaking is relatively weak. The experimental results can provide a reference for the seismic analysis of this kind of tailings reservoir.

Deformation joints are universal in underground utility tunnels that belong to the shallow-buried and slender structure. Under seismic loads, the vibration response of the underground structure with a joint will be affected to a great extent. However, the studies on this problem are limited. In this paper, based on the shaking table model test that considers the influence of joints, the seismic response characteristics of the underground utility tunnel under seismic excitation with different waveforms and different peak accelerations were studied. The acceleration, soil pressure, displacement, strain, and bending moment were measured and analysed. The results indicated that the vibration of the tunnel was mainly affected by the surrounding soil and the sidewall of the joint section separated from soil during earthquake excitation, while the tunnel structure displayed a good integrity. The displacement of the tunnel joint was relatively small under the strong earthquake, which did not result in large-scale deformation failure. The distribution of seismic soil pressure under the strong earthquake was nonlinear. The moment on the joint section was less than that in the middle section in the earthquake, which was beneficial to seismic performance.

In order to study the discontinuous fatigue failure evolution process of surrounding rock of underground salt cavern gas storage under intermittent cyclic loads of injection and production, triaxial interval fatigue tests on deep salt rock from Pakistan was carried out, and the effects of confining pressure and stress level on the interval fatigue of salt rock under triaxial condition were analyzed. The results show that: Compared with uniaxial interval fatigue, confining pressure not only improves the compressive strength of salt rock specimens, but also increases the fatigue life of salt rock. The higher confining pressure results in a more significant increase in range. In triaxial interval fatigue tests, the residual strain of the stress cycles after intervals is larger than that before the interval, which is consistent with the results from uniaxial interval fatigue tests. However, the increase of confining pressure will lead to a decrease in the residual strain accumulation and the residual deformation difference between the cycles before and after the interval. With the increase of stress level, the residual strain and the difference of residual strain before and after time interval both show an increasing trend.

In view of the serious cross grouting and overflows grouting in the construction of conventional grouting technology, and the unsatisfactory effect of stratum reinforcement, the grouting technology of mold bag sleeve valve tube is often used in advance grouting construction of tunnels. But at present, the selection of mold bag grouting pressure is mostly based on experience. In this paper, it is considered that the mold bag keeps cylindrical expansion during grouting and forms a stress-affected zone consisting of elastic and plastic zones in the surrounding compacted soil. Based on the elastic-plastic theory and considering the non-correlative flow rule in the plastic influence zone of surrounding soil, the expressions of the relationship between the initial radius R0 of grouting, the radius Ru of grouting reflection and the radius Rp of plastic zone of soil during the mold bag grouting process are derived, and the theoretical formula for calculating the mold bag grouting pressure P can be derived. The results of parameter analysis show that the grouting pressure is significantly affected by the elastic modulus, internal friction angle, cohesion and initial stress of the soil. The theoretical formula of mold bag grouting pressure was applied to the grouting project of the sleeve valve tube of the People's Hall Station. From the variation rule of grouting expansion radius Ru with grouting pressure P, it can be concluded that when the grouting effect on the surrounding soil is the best, the grouting pressure of the mold bag is 2.0 MPa and the final expansion radius of the grouting body is 20 cm. The test results of grouting effect show that the sealing batholite of mold bag grouting expansion has successfully controlled the grouting diffusion, and achieves the expected effect of controlling grouting area.

The baffle, as a kind of mountain disaster protection structure, can effectively dissipate the movement energy of rock avalanches and restrain the movement distance and speed of rock avalanches. The construction of a baffle’s speed bumps between the rock avalanches gully and the disaster zone can greatly protect the disaster zone. In this study, based on the physical model experiment, the dynamic impact response of the channelled rock avalanches is implemented on the arc-shaped, square and cylindrical baffles. The effects of three types of baffles on the motion performance of channelled rock avalanches are discussed, and the structural optimisation of the arc-shaped baffles is further investigated. The results show that the baffles can effectively reduce the channelled rock avalanches accumulation distance and control the movement speed. Among the baffles of these three shapes, the blocking effect of the arc-shaped baffles and the square baffles is more efficient than that of the cylindrical baffles. Owing to the concave shape of the arc-shaped baffles, the blocking effect is much better than that of square baffles on the deposit areas and deposit depth. At the same height and diameter, the arc-shaped baffle volume has 22.6% and 39.2% less than the cylindrical baffle and the square baffle, respectively. Thus, the production cost of the arc-shaped baffle is lower than another two baffles. When the row of the arc-shaped baffles is increased from one to three, its blocking rate is increased from 7.2% to 4.5% as well. An appropriate increase in Ld can improve the energy dissipation efficiency of the arc-shaped baffles. This can provide theoretical and technical support for the application of pile groups in channelled rock avalanches control engineering.

At present, the research on the consolidation deformation of soft soil under unloading mainly focuses on the instantaneous unloading. In order to clarify the evolution of consolidation deformation of soft soil under linear unloading, through the one-dimensional consolidation theory of Terzaghi and the principle of effective stress, an effective method is proposed to study the general solution of the soft soil foundation under the arbitrary unloading rate and solve the analytical solution of the consolidation equation under linear unloading. The results show that: 1) the negative excess pore pressure generated in soft soil foundation under linear unloading can be divided into three stages: growth period, rapid dissipation period and slow dissipation period; 2) unloading rate affects the growth path and dissipation rate of negative excess pore pressure; 3) and unloading affects the maximum negative excess pore pressure with the unloading amount approximately linearly increasing. Finally, taking engineering examples for comparative analysis, it is found that the negative excess pore pressure and its dissipation rate induced by unloading are the highest at the end of unloading. The theoretical results with evolution trends are in good agreement with field measurements.

The micro steel tube mortar composite pile is widely used in foundation reinforcement and pile replacement because of its clear force mechanism, simple construction, short construction period and low cost. However, there is rare theoretical study on instability or failure of micro steel tube mortar composite piles with small diameter and large length in soil. Therefore, on the basement of the theory of elastic foundation beam, the differential equation is solved according to the force relationship between the pile and the foundation soil. The specific expression of the bearing capacity for instability of the micro steel tube mortar composite pile is given. By comparing with the actual engineering in situ test, it is found that the theoretical and experimental results are close. An expression calcuating the minimum critical length is given to guide the construction of the project. Through a program writen in Matlab, the instability load refering to different pile lengths is calculated and analyzed under different stiffness ratios between soil and pile, which reflects the influence degree of soil on the instability and restraint force of micro steel tube mortar composite piles.

Acoustic wave velocity is a comprehensive single index for evaluating the engineering geological characteristics of rock mass, such as compactness and hardness of rock, integrity, inlay and so on. It has been widely used in the rock quality inspection and consolidation grouting evaluation. In the prophase prospecting of Jinping I hydropower station, more than 22 000 meters cross-hole and single-hole sonic wave tests by the pressure plate in horizontal tunnel, as well as over 11 400 meters single-hole borehole sonic wave test were carried out. During the construction phase, more than 11 000 meters single-hole sonic wave test, 2 380 meters cross-hole and single-hole sonic wave tests in 263 holes as well as cross-hole and single-hole sonic wave tests by the pressure plate at 58 test points were carried out at the dam foundation and resistance body on the left bank. Then, the cross-hole and single-hole sonic wave tests of the two stages were analyzed based on the different statistical methods (length of hole and number of holes). The results show that the velocity of single-hole sonic wave (Vp) is generally higher than that of cross-hole sonic wave (Vcp). The ratio of Vp /Vcp ranges from 1.05 to 1.20. The velocity relationship between the single-hole sonic wave and the cross-hole sonic wave can be described by the formula Vcp =1.160 8Vp?1.023 2. And the correlation formula between the deformation modulus of rock mass and the single-hole acoustic wave velocity obtained by this formula can be used to predict the deformation modulus of different rock mass grades. The results above can provide basis for predicting the velocity of cross-hole sonic wave and deformation modulus of rock mass in similar hydropower and water conservancy projects.

The excavation damage zone (EDZ) in hard brittle country rock exhibits noticeable time effect after excavation, as rock strength varies with time caused by the high geostress, which leads to the development of surrounding rock excavation damage zone and shows time-dependent characteristics. The LSSVM-PSO intelligent inversion analysis method considering time effect was established based on the time effect evolution model of rock strength, and measured EDZ data collected in the test tunnel of Jinping Ⅱ Hydropower Station, such as borehole monitoring, ultrasonic test and deformation monitoring were used as target functions. The orthogonal design method, least square support vector machine (LSSVM) model and principle of particle swarm optimization algorithm were used to simulate the EDZ’s time effect evolution process between the time excavation ended and 25 days after in Jinping Ⅱ Hydropower Station. The study result shows: 1) Under high geostress, the principal geostress direction dominates the EDZ expanding, furthermore, the minimum principal stress direction is the main direction for EDZ extending and the failure zone (failure approach index, FAI≥2) also concentrates in this area. 2) The area of plastic zone after excavation develops to be “S” shaped curve. The area change of the plastic zone is relatively slow at beginning, then shows a linear increasing tendency and gradually becomes stabilized. 3) The plastic zone growth is rapidly increased from 3rd to 10th day after excavation, during which period rock burst is most likely to occur. The research results can provide guidance to the time effect characteristics of EDZ expanding in hard brittle surrounding rock mass under high geostress.

Shield-soil interaction is a complex multiphase coupling problem during the change of shield attitude. According to the critical attitude parameter of the shield pitch angle, based on the ground reaction curve, the shield-soil interaction relationship is simplified by using an equivalent soil spring, and a shield-soil interaction model is established. The initial boundary problem of shield-soil interaction is solved by the improved method of the loosening earth pressure of Terzaghi's theory. A theoretical calculation method of shield pitch angle is further obtained. Moreover, the effects of the vertical coefficient of subgrade reaction and upper-soft lower-hard ground on shield-soil interaction are analyzed and discussed. The results show that the upper-soft lower-hard ground is unfavorable to the control of the shield attitude, and the requirements for shield attitude control become high. Finally, the measured data of the pitch angle of the R2 line shield tunnel project of Jinan Metro are compared and analyzed. The results show that the deflection moment applied by the jacks cannot fully act on the shield, resulting in the measured values are generally slightly smaller than the theoretical value. The theoretical calculation method of shield pitch angle can provide theoretical guidance for shield attitude control.

A simplified mechanical model of dangerous soil mass-anchor bolt-stabilized soil mass anchorage system is established against the background of instability of rammed earth sites caused by wide vertical cracks. In this model, friction between the anchor bolt and the soil mass is simplified into a parallel mechanism of a linear spring together with a speed-related damper, and the connect effect of anchor bolt in crack section is simplified as a linear spring. Dynamic equilibrium equations for the anchoring system are established based on the theory of elastodynamics, and analytic solutions of dynamic response of bolt axial forces and displacement are deduced. Finally, the analytic method proposed by this paper is applied to the anchorage engineering of the southern wall of the Gaochang Ancient City in Xinjiang to analyze the axial force response characteristics and distribution law of the anchor bolt. The rationality of the procedure is verified by numerical analysis. The results show that the axial force response of the anchor bolt at the same position under dynamic action fluctuates around the static equilibrium position, the position of the maximum axial force is near the crack and gradually decreases exponentially toward the free end and the anchor end. And after considering the amplification effect of the seismic acceleration along the height of the site, a more accurate axial force response of anchor bolt can be obtained.

The buried pipes will be destroyed under traffic loading, which will have a great influence on the economy and life in this area. In recent years, waste rubber tire particles mixed with soil are gradually used as backfill soil for subgrade and other fields. In this paper, the dynamic characteristics of pipe buried in rubber-silt lightweight mixtures under impact loading were investigated. In this study, 0%, 10%, 20% and 30% waste tire particles were added into the foundation soil by equal volume replacement method. The vibration absorption performance of light mixed soil as subgrade filler was studied through the surface settlement of subgrade and the deformation characteristics of buried pipeline. The results show that the addition of rubber particles to silty soil can effectively reduce the surface settlement of model soil. The settlement reduction is the most obvious with the 10% rubber content. The buried pipe shows a shape of "flattening" under impact loading. The addition of rubber particles can significantly reduce the strain and bending moment response of the buried pipe. When the rubber content is 20% and 30%, the strain and bending moment of the buried pipe decrease more obviously.

The cracks on the ground surface will form a complete crack system gradually with the increase of the slope deformation. In view of the rainfall infiltration process of this type of landslide, it is pointed out that the preferential flow penetration developed along the dominant channel formed along the surface crack leads to the deterioration process of landslide stability and promotes the development of deformation. This paper systematically analyzes the relationship between the preferential flow penetration, the fluctuation of groundwater level and the slope deformation. Taking the Wangjiapo landslide as the research object, the temporal-spatial deformation evolution of the dominant channel and the corresponding deformation characteristics are studied, and the starting and ending points of the irregular "step" shaped deformation acceleration interval on the cumulative displacement deformation curve are named as the "acceleration point" and "deceleration point". And then, the groundwater fluctuation rule in the process of landslide deformation is inverted and the related stability evolution rule is obtained by using monitored data of W3 monitoring points. It is found that the "acceleration points" and "deceleration points" of the deformation acceleration interval of landslide are consistent with the starting and ending points of the stability changes. The method for determining the deformation acceleration interval can be established, and then the displacement rate threshold is determined.

The submarine pipeline laid on the shallow foundation of the deep sea is prone to axial expansion and contraction under the action of high temperature and high pressure during operation, and this movement will intermittently shear the shallow soil around the pipe. Therefore, it is necessary to investigate the mechanism of tube-soil interaction during the axial movement of the pipeline. In this paper, a small strain finite element analysis of the axial motion of a shallowly buried pipeline during operation is established based on the modified Cambridge model. In the process of axial movement of pipelines with different initial depths, the development curve of axial resistance (S-shaped consolidation curve) in critical plastic shear consolidation stage is fitted. The variations of the excess pore water pressure, the friction coefficient of the pipe-soil interface, the wedging factor ζ and the axial resistance between pipes and soils are discussed. It is found that the peak excess pore pressure generated by axial shear is a function of velocity and time. As the axial velocity decreases, the value of the peak excess pore pressure decreases and the time point of the peak pore pressure is delayed. The internal mechanism of the transition from undrained condition to drained condition in the process of axial movement is expounded.

The upper-bound finite element method with rigid translatory moving elements (UBFEM-RTME) is further improved to optimise its suitability for analysing the stability in heterogeneous clay. The method is applied to investigate the stability of the tunnel face in undrained clay layer subjected to surface surcharge. The variation of stability load ?s /cu0 and the morphological characteristics and discipline of the effective discontinuities mechanism are obtained for various combinations of dimensionless buried depth ratio C/D, dimensionless gravity parameter ?D/cu0 and the heterogeneous parameter ?D/cu0. The results reveal that C/D and ?D/cu0 have a significant effect on ?s /cu0 and failure mechanism. ?D/cu0 has a great influence on ?s /cu0 but has little effect on failure mechanism. Furthermore, the UBFEM-RTME is used to show the changes of mesh failure modes under different mesh parameters such as the number and distribution of effective discontinuities, and the reasons for improving the accuracy of the upper bound solution are also explained. The applicability of UBFEM-RTME in heterogeneous clay, especially the analysis of failure mode under the limit state, is verified in comparison with the existing rigid-block upper-bound limit analysis methods and finite element bound method.

Polarization effect of shear wave is mainly utilized to obtain shear wave arrival time in downhole method of shear wave velocity test. However, the polarity of the P-wave of received signals is observed to be reversed in in-situ tests. Therefore, it is vital to study the theoretical basis that the P-wave keeps the same polarity while the shear wave changes polarity. A three-dimensional finite element numerical model was established in order to simulate the polarization effect of the downhole method excited by surface forward and reversed hammer strike. The vibration responses under surface excitation at different depths were analyzed by time-domain lumped mass dynamic finite element method with an explicit step-by-step integration. It is shown that both S-waves and P-waves are clearly observed to be 180 degrees phase difference from the horizontal signal traces with the direction of excitation generated by reversed impulse, which is contrary to the practical engineering cognition. In order to find out the reason behind this phenomenon, numerical simulations of three possible scenarios (inclined excitation, geophone deflection and geophone inclination) were carried out. The results indicate that the combined influence of inclined excitation and geophone inclination is the main cause that leads P-wave to keep the same polarity while the shear wave changes polarity. Furthermore, a method based on the time interval during load peak and response peak is proposed to obtain reliable shear wave velocity, which is verified to have a shear wave velocity closer to preset velocity of the model in numerical simulation and better than that from the peak to peak method and cross-correlation method.

The traditional numerical manifold method (NMM) adopts the form of regional integration. This paper proposed a new NMM in the form of boundary integral by integrating the advantages of both the boundary element method (BEM) and the NMM, namely the dimension reduction of BEM and the flexibility of local base selection of NMM. For two-dimensional elastostatics problems, three different benchmark examples with analytical solutions are applied to verify the validity and efficiency of the newly proposed NMM. The results show that the accuracy of the proposed procedure can be effectively improved by increasing the order of the local basis.

A numerical model for simulating variably-saturated flow in fractured porous media is established using the composite element method. The model has the following features. The fractures do not need to be discretized into specific elements, but are inserted into the porous matrix elements according to their geometric positions to form the composite elements. Within the composite element, the calculation equations for the fracture flow and the porous matrix flow are built respectively, which can be linked by the fracture-matrix interface and integrated into the composite element equation. The composite element equation has the same format as the conventional finite element equation, so the solving techniques for the conventional finite element equation can be applied to the composite element one. Using the techniques of under-relaxation iteration, mass matrix lumping and adaptive time-stepping, a calculation program for variably-saturated flow in fractured porous media is developed. The rationality and applicability of the model are verified by simulating the one-dimensional infiltration into dry soils and the flow in complex fractured aquifers. The simulation results provide a theoretical basis for further understanding groundwater flow characteristics in unsaturated fractured aquifers.

The direct roof of weak stratum in roadway has three kinds of failure modes: deflection failure, integral caving and arch caving. The change of roof thickness is one of the main reasons affecting the failure modes. Therefore, based on beam theory and block theory, a mechanical model of roof rock beam-block was constructed to reveal the changing law of the direct roof failure form in weak strata of roadway. On this basis, the safety factors of flexural failure and shear failure were defined, and the calculation models of critical thickness of the roof with different failure modes were established to determine the corresponding failure modes of the roof with different roof thicknesses. The case study shows that with the increase of roof thickness, the failure mode of the roof gradually changes from flexural failure to integral caving and then to arch caving. At the same time, when the thickness of the roof exceeds a certain value, the height of the caving arch no longer increases in a substantial manner. Based on the same engineering conditions and mechanical parameters, a comparative analysis between numerical simulation and a case calculation was carried out. The critical thickness of the roof under the case calculation conditions was 0.14 m from flexural failure to overall collapse, and 0.8 m from overall collapse to arch collapse. The numerical simulation and case calculation results were consistent. It shows that the calculation model of the critical thickness of the roof can effectively determine the failure form of the roof. The research results can provide theoretical reference for direct roof control and support scheme design of mine roadway in weak stratum.

At present, the determination of rock mechanical parameters is limited to the probe and data acquisition equipment, which can only be used in the laboratory environment. At the same time, the traditional ultrasonic transceivers have high requirements for the contact surface roughness. Therefore, there is a need to polish the rock surface, and to apply sound guide paste before the analysis. The aforementioned issues have greatly limited the scope of the application of ultrasonic measurement systems. In order to achieve long-term monitoring in rock boreholes, the sound wave emission and reception mechanism and the frequency domain characteristics of the ultrasonic signals in the rock were analyzed in this study. The wavefront first arrival was picked up by the AIC algorithm, and the wavelet denoising and the improved AIC method (NAIC) were utilized to find the exact wave arrival time, and the internal parameter measurement system based on dry coupling rock was studied. The ultrasonic signal transmission and reception, signal transient triggering, and high speed acquisition were achieved inside the rock, and the final result was wirelessly transmitted to the data recorder. Ultrasonic transmission parameters were measured for Φ50 mm×100 mm granite and sandstone rock samples. The measurement distances of Φ114 mm×280 mm granite rock samples were 150 mm and 200 mm with the use of NAIC, STA/LTA, MER and ETA algorithms. The data was processed and compared to the results of third party instrument measurements. The results show that the system based on dry coupling acoustic wave velocity measurement has good adaptability to different working contact surfaces, and the data error is within the allowable range of the specification. Wavelet denoising is suitable for ultrasonic receiving signals with less background interference and concentrated frequency range. In terms of picking-up, the other three algorithms except STA/LTA can effectively improve the pick-up accuracy after denoising. NAIC is the method with the most significant error reduction, and the average error is reduced from 1.21 ?s to 0.19 ?s.