The loosened zone around a pipe must be considered when the mechanism of backward erosion is investigated. However, few quantitative analyses were found in the literature regarding the permeability characteristics of the loosened zone around a pipe. The present paper focuses on the process of grain loosening and permeability changes of surface soil by sand column experiments subjected to upward vertical flow. The loosening top soil and downward progression of the loosened zone were observed in sand column experiments, indicating that the seepage failure modes of the top soil and the mode of whole sand column are different. Analysis of the hydraulic head distribution along the sand samples showed that the permeability of loosening top soil occurred as an abrupt change. The permeability coefficient of the thin loosened zone at the surface is larger than that of the following loose sand. Similarly, the permeability coefficient of part of the loosened zone around the pipe is larger than that of the original sand, resulting in insufficient gradient near the pipe tip. The finding is essential for investigating the erosion mechanism near the pipe tip.

According to the stress variation of fractured rock mass, the horizontal stress, vertical stress and water head pressure of mining stope were simulated by the normal load, shear load, and seepage water pressure during the mining process, respectively. In this study, the compression-shear seepage coupling experiment was conducted by using JAW-600 type shear seepage coupling testing system. Then the effects of normal load of fractured rock mass, roughness of joint, and seepage water pressure on the displacement, stress and permeability of specimens were discussed under the conditions of constant normal load (CNL) and constant normal stiffness (CNS). Besides, the influence laws of the shear displacement and dilatancy properties of fractured rock mass on shear stress, normal displacement, the hydraulic opening of joint and permeability were analyzed as well. It is shown that the hydraulic opening of fractured rock mass was promoted by shear stress and water head pressure, whereas its change was inhibited by the horizontal stress. Moreover, the hydraulic opening was divided into three phases, namely smaller or unchanged phase, increasing phase, stable phase with the change of shear displacement. It is found that the greater final stable value of hydraulic opening depended on the higher roughness of joint and the lower stiffness of fractured rock mass. In addition, the permeability firstly decreased and then increased owing to the dilatancy of fractured rock mass. The permeability increased with the increase of shear displacement and the roughness of joint surface, but decreased with the increase of normal load. Therefore, this study can provide the theoretical basis for the permeable channels, initiation and outbreak of permeability disaster evolution process in fractured rock mass.

It is significant to analyze the waves induced by buried sources from the point view of the geoengineering prospecting. Based on the mode superposition method, displacement expressions were presented for waves in the homogeneous half space induced by buried spherical and dilatational point sources. Then the excitability and propagation behavior of Rayleigh waves were investigated, and the mechanism of the excitability was also analyzed. In addition, the reliability of the proposed method was verified by numerical simulations. It is shown that the excitability of Rayleigh waves was related to the ratio of buried depth to the wavelength. It is found that the lower the ratio was, the higher the excitability was. However, Rayleigh wave was not easily activated when the ratio was greater than 1. Compared with the normal Rayleigh waves which propagate in the planar wavefronts in the free state, the phase velocity of Rayleigh waves activated by buried sources varied with the propagation distance. Particularly, the activated Rayleigh waves had the spatial behavior. The nearer the distance from the axis was, the lower the phase velocity of the vertical vibration was. When the distance was beyond one wavelength, the phase velocity of the activated Rayleigh waves approached that of the normal Rayleigh waves.

The aim of this study is to investigate the effects of construction sequences of twin tunneling at different depths on the adjacent pipeline. A three-dimensional (3D) centrifuge model test was conducted by considering both the volume loss effect and the weight loss effect during the tunnel excavation. Moreover, the corresponding numerical simulation of this centrifuge model test was carried out, which further considered a displacement controlled method based on ground loss and an advanced hypoplastic constitutive model based on nonlinear small strain characteristics of soil. It reveals that twin tunnels at different depths with various construction sequences greatly affects the greenfield surface settlements, the pipeline settlements and the pipeline bending strain. After the twin tunneling, the sagging regions are located within the range of -2.5DT－1.5DT and the maximum bending strain within the sagging regions is around two times that within the hogging regions. The results indicate that the superposition principle cannot be simply applied to predict the surface settlements, the pipeline settlements and the pipeline bending strain caused by twin tunneling at different depths with various construction sequences. The effects of the accumulated shear strain and the relative pipe-soil rigidity should be reasonably considered.

This study is to investigate the mechanical anisotropy of shale reservoirs at different depths. Uniaxial compression experiments were conducted on Longmaxi formation shale to explore horizontal and vertical variation laws of mechanical parameters. Meanwhile, anisotropy indexes of mechanical parameters of shale reservoir were comprehensively analyzed. It is found that mineral content, development of natural fractures, the denseness of bedding slit in shale reservoirs all exhibited mechanical anisotropies at a certain degree. With deepening the sampling depth, the elastic modulus decreased. Meanwhile, the Poisson’s ratio had a seesaw high-middle low phenomenon, whereas the compressive strength opposite. In addition, horizontal and vertical anisotropy indexes of the compressive strength were much higher than those of the elastic modulus and Poisson's ratio under the same environmental condition. Moreover, the anisotropy index of the compressive strength varied in a larger scope. Horizontal and vertical mechanical anisotropy indexes reflect the spatial distribution of mechanical properties to some extent. Therefore, the mechanical anisotropy should be investigated at different depths and in different directions in advance when constructing the deep rock engineering. The constitutive relation of rock mass also should be properly chosen to optimize the construction. ,

With the increase of excavation depth of underground cavern, temperature has become the important factor influencing the long-term stability of the cavern. In order to reflect the influence of the temperature on the long-term stability of surrounding rock, the triaxial creep tests with different stress paths and temperature conditions were conducted relying on a hydropower station headrace tunnel engineering, and the influences of the temperature, confining pressure and axial pressure on the creep deformation characteristics, the creep strength and the creep failure mode of gneissic granite were analyzed systematically. The test results indicate that the creep properties of gneissic granite are exponential with the increase of loading stress and temperature. Gneissic granite possesses creep stress threshold, and with the increase of the temperature, the threshold lowers, the time of creep failure becomes shorter. The steady-state creep rate of gneissic granite increases exponentially along with the rise of temperature. The long-term creep strength and creep rupture strength decrease with the increase of temperature. Creep failure modes of gneissic granite are mainly shear failure along the inclined section. The results provide important experimental basis for the long-term stability analysis and design and the construction of hydropower station headrace tunnel.

Considering the stress history and initial stress anisotropy of natural saturated clay under K0-consolidated condition, a theoretical solution to the jacking force of pile was derived by modeling the pile shaft penetration process as the spherical and cylindrical cavity expansions, respectively. Then, based on the radial excess pore water dissipation after the pile installation, an analytical solution to the time-dependent bearing capacity of the jacked pile was derived by considering the relaxation effect of the soil around the pile during reconsolidation process. And the theoretical expression for the timeliness coefficient of jacked pile bearing capacity in K0-consolidated natural saturated clay was established. The validity of the present solution was verified by the centrifuge model test and field test respectively, and the time-dependent bearing capacity were discussed in detail. The results show that, the time-dependent bearing capacity within a short time after pile installation can be attributed to the combination of the excess pore water pressure dissipation and the thixotropy recovery of the surrounding soils. After a certain rest time, the dissipation of the excess pore water pressure is the main reason for the increase of the bearing capacity.

To study the effect of soil structure on deformation characteristics, a series of odometer and mercury intrusion porosimetry tests on undisturbed, remolded, reconstituted and compacted samples of Shanghai soft clay, was carried out to obtain the compression curves and the pore-size distributions (PSD) of samples. The test results show that consolidation pressures and sample preparations have important influence on the PSD curves, and the PSD of undisturbed sample of Shanghai soft clay exhibits a unimodal shape, with a pore-size mainly ranging from 0.01 to 1.0 ?m. The unimodal PSD of undisturbed sample is greatly influenced by soil structure. Large and medium interparticle pores are compressed into the small interparticle pores with increasing consolidation pressures, particularly under the consolidation pressure larger than the structural yield stress. The unimodal PSD also was found in saturated soft clay, no matter undisturbed, remolded, reconstituted or compacted samples. However, the PSD curves of samples using different sample preparation methods are different. The compacted samples have larger pore size and the reconstituted samples generate uniform pore size. The differences of micro-pore structure among different samples will be reduced with increasing consolidation pressure, yet never eliminated even at large consolidation pressure. Lastly, the reference void ratio, i.e., a simple expression of clay fabric, is used to normalized the compression curves of the samples with different preparation. Different compression curves of four types’ samples are normalized to a high correlative unified compression curve, which shows that the reference void ratio is a reasonable and effective parameter to illustrate the PSD of clay.

To better describe the damping behavior of rock, a new method was developed to calculate damping parameters in consideration of lateral and longitudinal damped vibrations. A series of damping experiments was also conducted on sandstone, conglomerate and glutenite under dynamic cyclic loading, the stepped cyclic loading and the constant amplitude cyclic loading, respectively. Then response characteristics of damping parameter to stress amplitude and strain amplitude were both obtained. This study revealed the evolution laws of the damping ratio and the damping coefficient with the cycle number under the constant amplitude cyclic loading. In addition, an empirical model was derived for the evolution of the damping ratio with the cycle number, based on the laws of entropy conservation and energy conservation. From experimental results, the damping ratio of rock increased with increasing the axial strain amplitude under dynamic cyclic loading, whereas the damping coefficient decreased. Under stepped cyclic loading, the damping ratio and damping coefficient of rock increased with the increase of axial stress amplitude. It is found that the threshold for the fatigue failure of sandstone was the point where the evolution law of dissipation energy and damping changed suddenly. If the upper limit of stress was higher than the threshold for fatigue failure, all evolution curves of the dissipated energy, the damping ratio and the damping coefficient were half U–shape and characterized by three phases. On the contrary, their evolution curves were characterized by L-shape and two phases. Through the damping ratio experiments of sandstone, it is verified that the model was capable of describing the energy dissipation and the damping behavior in constant amplitude cyclic loading process.

By using the method of loading and unloading at the relative lossless low-stress level without causing a large additional damage, freeze-thaw cycle tests were conducted by considering the time effect. In the case of limited experimental cost, the number of rock samples required can be drastically reduced. Compared with the conventional test method, this novel procedure can obtain more efficient data from the limited data of certain rock samples without subjectively screening testing data due to the discreteness of samples. With the increase of the number of freeze-thaw cycles, the pore and micro-cracks on the surface of rock specimen are expanded and a softening layer is formed. The crack is deepened and the degree of particle shedding is aggravated. The occurrence of erosion makes moisture moving to the inside of rock specimen, and the degree of freezing and thawing damage gradually deepens from inside to outside. The development of titration technology calibrates the gradual damage. We further analyzed the dynamic response of rock samples under different upper limit stress cycles with different freezing and thawing cycles. The results show that the damping ratio, the damping coefficient and the dynamic Poisson’s ratio are linearly increasing with the number of the freeze-thaw cycles. The dynamic elastic modulus decreases linearly with the number of the freeze-thaw cycle, but increases linearly with the amplitude stress. However, the damping ratio and dynamic Poisson’s ratio decrease linearly with the amplitude stress. The quantitative relationships are established between the damping ratio, the dynamic Poisson’s ratio, the damping coefficient and the dynamic elastic modulus. One known parameter can be used to predict the changing pattern of other parameters. Under the limited testing conditions and times, the numbers of parameters to be tested can be effectively reduced. If the amplitude stress is greater, the response of elastic deformation is more rapid, the irreversible deformation is smaller, and the energy absorbed is less. With the increase of the number of freeze-thaw cycles, the slope loading section of rock specimen gradually becomes longer, and the slope of the stress-strain curve becomes smaller before loading and unloading. The axial strain of rock specimen is linearly related to the number of freezing and thawing cycles after loading and unloading when the stress limit is reached for the first time in each cycle. It indicates that the porosity of rock specimen under the freeze-thaw cycle is gradually increased while the degree of density reduces. Rock specimens tend to soften gradually. When the amplitude stress is high, the plastic accumulation of rock specimen expands in the exponential relationship with the number of freeze-thaw cycles. However, when the amplitude stress is low, the plastic accumulation increases in a linear relationship with the number of freezing and thawing cycles. It is shown that the amplitude stress is significant to accelerate deterioration.

The peat soil is a special soil which has obvious regional characteristics. A series of staged cyclic loading triaxial tests is performed to investigate the dynamic deformation properties of the peat soil in Kunming under the conditions of different confining pressures, different consolidation ratios, and different loading frequencies. The effects of confining pressure, consolidation ratio, and loading frequency on the deformation properties of the peat soil subjected to cyclic loading are evaluated through analyzing the dynamic backbone curve, stress-strain hysteretic curve and dynamic elastic modulus. Results show that the dynamic strain of peat soil increases nonlinearly with the dynamic stress amplitude, and there exists a critical stress value at the backbone curve. When the dynamic stress amplitude acting on the soil reaches its critical stress value, the strain of peat soils grows rapidly, and then the soil structure is destroyed; the confining pressure has the most significant effect on the dynamic deformation properties of peat soil, followed by the consolidation ratio, loading frequency is the minimum; the effect of consolidation ratio on the dynamic deformation properties of peat soil depends on the value of confining pressure, which is greater under higher confining pressure; the elastic deformation of peat soil decreases as confining pressure and consolidation ratio increase, while increases as loading frequency decrease, at the same loading level; the stiffness of peat soil decays as loading cycles and loading level increase, the plastic deformation appears and cumulatively grows up; the larger plastic deformation is observed in peat soil with increasing confining pressure and consolidation ratio, decreasing loading frequency.

This study is to investigate the influence of different chemical solutions and soak time on the mechanical characteristics of sandy slate. Uniaxial compression tests on sandy slate samples are conducted to determine the variations of relative mass, deformation and strength characteristics of sandy slate under different water chemical corrosion conditions. The changes of pH,Ca2+ and Mg2+ concentration of chemical solution are monitored in soaking process. The corrosion mechanism of sandy slate sample soaked by chemical solutions is discussed based on the results of SEM. The results indicate that: with the augmentation of the solution acidity, the corrosion degree of sandy slate increases gradually; sandy slate presents strain softening subjected to chemical solutions, and the softening effect is more evident with the increase of the solution acidity and soak time; the peak strength of sandy slate declines as soaking time extends; the different types and degrees of water-rock interaction lead to different changes in microstructure of sandy slate, presenting loss of cementing material in neutral solution or dissolution of large numbers of mineral particles with large size in acidic solution.

Toothed piles with sand liner are composite loaded piles which are formed by combining sand liner and pre-stressed pipe pile. Based on the spherical cavity expansion theory, this paper analyzes the impact of cavity expansion on the soil around and beneath the pile. The results indicate the mechanism of axial load capacity of toothed piles with sand liner. The results show that the side friction force consists of two parts, i.e. the friction force between soil and pile, and shear force of remolded soil between pile and teeth. We made a correction to the coefficient of soil disturbance in the equation to consider the effect of soil disturbance during the piling process. The paper also analyzed the proportion of toothed pile shear force in the total pile bearing capacity. The calculation results and its theoretical equation are proved to be correct and reliable based on verification with national regulation, provincial standard, theoretical derivation formula computing result and the static load test on site. This research methodology provides the theoretical basis for future application and improvement of toothed pile in future production. The research conclusion also has practical significance.

Based on radial consolidation theory and equal stain assumption, third-order quasilinear partial differential equations for ultra-static pore water pressure of drainage are deduced under cylindrical coordinate system. The equations consider the effects of vacuum pump failure, air leakage, and the spatial and temporal nonlinearity on drainage well resistance. The variation of vacuum degree under film with time is used as a boundary condition, the analytic solutions for consolidation of vacuum preloading foundation under self-weight are derived with the consideration of influence of air leakage and the permeability coefficient of drainage water decreases with depth linear attenuation and time exponential decay. By comparisons, the solutions given by previous studies are found as a special case of the general solution in this article. Through examples, the results show that the well resistance coefficient A2 on the degree of consolidation is sensitive than A1, and the air leakage has a direct impact on the consolidation degree of the foundation in the process of vacuum preloading. The consolidation is slower under serious air leaking conditions. Therefore, the vacuum preloading time should be extended to ensure the vacuum pre-pressure results.

This paper is to investigate mesoscopic features of coal seam and rock mass in the deep field, which includes the mineral, configuration, and structure of the fractured surface of specimens. The effect of confining pressure on creep damage mechanism and its regulation were also studied. Under short period creep loading, the observed mesoscopic features were classified into cleavage fracture-joint fractures, intergranular fracture, and intergranular-transgranular fractures under confining pressures of 0, 10, and 20 MPa, respectively. Under the confining pressure of 0 MPa (i.e., the uniaxial creep test), the failure fracture was caused by the simple stress acting on coal seam and rock masses directly. As a result, its cleavage fracture and joint fissure had distinct structure, clear orientation, and fresh interior without inclusions. Under the confining pressure of 10 MPa, the interface of intergranular fracture was found to be relatively wide, and the interior was not clear and filled with inclusions. It indicated that the grain boundary was easily broken under the higher confining pressure, and the mineral structure was changed by adjusting both the tangential movement among grains and the grain rotation under the action of torque. Under the confining pressure of 20 MPa, since the grain boundary was restricted and grain itself was difficult to be destroyed, the ultimate destruction of the fracture along the grain boundary fracture mainly showed the arc rotation. Besides, the siginificant feature of transgranular fractures was characterized by the shear displacement. Under strong restrictions, intergranular fracture structure was not clean and filled with little new inclusion caused by the earlier period of confining pressure. In contrast, the transgranular fracture was tiny, fresh, and pure without inclusions.

Solidification tests were performed on dredger fill mud with high moisture content in Binhai New Area of Tianjin using the powder curing agent. The effects of moisture content, curing time, and curing agent content on the strength of solidified soils were analyzed. The test results show that the most appropriate curing agent content is 3% considering the strength demand of economic rationality. The unconfined compressive strength with the curing duration of 60 days was defined as a benchmark. An equation for predicting unconfined compressive strength of the solidified soils was proposed using two variables, i.e., water cement ratio and curing time. The long-term strength properties of solidified soils with the moisture content of 160% and the age of 28 days were analyzed by the triaxial rheological tests. The test results show that the solidified soils present similar creep behaviors to the structural soft clays. Meanwhile, the long-term strength of solidified soils can be determined using the isochronous curve. The shear strength indexes under long-term loads can also be determined, providing theoretical support for the security applications of solidified soils.

Soil-water characteristic curve is the basic trait to reflect the existence state and interaction of three-phase medium in the unsaturated soil, and the soil-water characteristics of unsaturated soil will be influenced by the stress state change and the deformation development. To reveal the change rules of soil-water characteristic curve in complicated stress state, a series of isotropic consolidation and shear tests with different intermediate principal stress ratios b under constant water content is performed on intact loess with various initial suctions by using the improved unsaturated soil true triaxial apparatus. Soil-water characteristics of unsaturated intact loess under different test conditions are determined and illustrated, at the same time, the function of fitted curves is gained. The results show that saturations all increase with net mean stress, the ratio b and net confining pressure; the suctions decrease with the increase of saturations, when the saturation is larger (Sr0≥43%), the reduce rate of the suction is smaller, when the saturation is smaller (Sr0<43%), the reduce rate is larger; when the saturation is fixed, the suctions all increase with net mean stress, the ratio b and net confining pressure. The influence of small net mean stress (p≤300 kPa) on soil-water curve of intact loess after the completion of the isotropic consolidation is slight, which can be described by power function. A fitting expression of soil-water characteristic curve is obtained to reflect the combined effect of the net confining pressure and the middle principal stress after the completion of true triaxial shear. Applicability of the fitting expression is verified by relevant tests.

Laterally loaded monopiles are commonly used for the offshore wind turbines, which means huge moment is applied to the monopiles. Lagrange multipliers are constructed to describe the balance of the moment and the lateral force. The functional extreme problem of the deflection curve is then transformed into nonlinear equations. Based on the matrix operations of Matlab, Newton’s method is applied to solve the equations. This new method is available for any nonlinear or segmented p-y curves. The algorithm can be efficiently used to obtain the deformation of piles at varied load and design parameters. Data of testing piles is examined, which shows good reliability of the numerical results. Numerical examples show that when the loading height is approximately the same as the pile length, almost all the deformations are induced by the moment, thus the checking of lateral bearing capacity becomes meaningless. Finally, the design of a monopile foundation under an offshore wind turbine is studied. Deformations of the piles with different lengths and diameters are calculated. The results of calculations reveal an effective length of the pile. The diameter of the pile is determined by the limit of lateral displacement. Pile with significantly smaller diameter will meet the limit of rotation angle.

To investigate the effect of sulfuric acid corrosion on the mechanical behaviors of the pile-soil interface, large-scale direct shear tests were conducted on the interface between sand and concrete slabs under corrosion of 0, 31, 93, 154 days in sulfuric acid solution. Tests measured the relationship between shear stress and shear displacement of sand-corroded concrete interfaces after different corrosion durations. Experimental results indicate the hyperbolic relationship between shear stress and shear displacement. The shear failure of interface agrees well with the Mohr-Coulomb strength failure criterion. As the corrosion time increases, the cohesive force on the interface decreases, and the friction angle of interface, the shear strength and the shear displacement at the peak shear stress increase. Sand concrete interface failure tends to fail by sand itself under shearing. The shear displacement corresponding to the peak shear stress at interface between uncorroded concrete and sand is referred to as a standard. By comparing the interfacial shear stress with different corrosion times with the standard shear displacement, the shear stress after 5 months of corrosion is found to be smaller than that of uncorroded one. Finally, hyperbolic model is established and its parameters are obtained through the fitted relationship between tested shear stress and shear displacement, which provides a reference for further numerical simulation.

Underground pipelines used to transport fresh water, natural gas and petroleum are especially vulnerable to earthquake due to its long and deep features. Moreover, they have enormously adverse effects on emergency rescue, energy transportation and restructure after the earthquake. Non-uniform wave propagation triggered by the earthquake is considered as one of the most important causes which destroy long deep underground pipelines. Recently, the problem has drawn extensive concerns. However, there are few studies of shaking table tests on a pipeline under non-uniform earthquake excitation due to the limited experimental equipment. For a long deep underground pipeline, the large-scale double independent controlled table was utilized to study the response of underground pipelines under three-directional non-uniform earthquake excitation. Then the responses of acceleration, strain and displacement of pipelines were discussed under different types of earthquake excitation. From experimental results, different impacts of deep underground pipelines were obviously found on the motions of the ground surface and soil surrounding with the pipeline. In addition, the differences of bending strains of pipeline were great under non-uniform excitation and uniform excitation. If the bending strains of pipelines under earthquake excitation are designed to weaken or even ignore, it is difficult to explain the bending buckling failure of underground pipelines.

After the impoundment and operation of reservoirs, the water level changes slowly or rapidly between the flood control water level of 145 m and the impoundment water level of 175 m every year. Rock and earth mass in the hydro-fluctuation belt is under cycle of drying-wetting conditions for a long time. The degradation of mechanical properties direct impacts on deformation stability of the bank slope. In this study, the experiments of testing under drying-wetting conditions are designed and conducted on the soils from the typical hydro-fluctuation belt. The results indicate that: 1) Shear strength of soil degrades under drying-wetting conditions. Specifically, shear strength deteriorates 75% by the first 4 cycles of the drying-wetting, and gradually becomes stable afterwards. 2) During the drying-wetting cycle, the internal microscopic cracks of the soil samples open and close repetitively, and then gradually grow and assemble; dense soil samples gradually loosen with increasing internal cracks. 3) Considering the degradation of soil properties during the drying-wetting cycles in hydro-fluctuation belt, the local safety factor of slope will degrade accordingly. The local slide and the developed cracks can be easily observed near the hydro-fluctuation belt in field investigation. The findings in this article can provide good reference for long-term deformation and stability evaluation on slopes in hydro-fluctuation belt.

In general, uneven frost heave deformation was generated in upper soil strata during the freezing reinforcement process of shield junction, which was caused by the frost heave effect of the irregular frozen wall. Hence, this study was to obtain the influence law of strata deformation caused by the frost heave effect. Based on the similarity theory, a model test was carried out according to the prototype of the freezing reinforcement project of shield junction in Shanghai, and then the deformation data were analyzed. The results show that the upper strata deformation caused by the frost heave increases linearly with increasing the frozen wall thickness in the freezing process. When the development of the freezing wall exceeded the measuring point, the stratum deformation at the corresponding position no longer changed. It is found that the frost heaving force caused by the frost heave extrudes the upper strata in the freezing process, which increases both the strata deformation and its average strain with increasing the depth of measuring points. When the frost heave force exceeds the cohesion of soil, the growth of the average strain terminates due to the slide occurrence in upper soil layers. Moreover, the strata are no longer subjected to compress, and the deformation of the bottom stratum transfers directly to the upper strata. The results indicate that the frozen wall thickness is the primary factor and the formation depth is a secondary factor, which both affect the upper strata deformation .

Oblique load is one of the most important loading forms of pile foundation in applications such as offshore, transmission line tower engineering, etc. However, the current calculation method for this problem is relative immature. Piles were divided as free section and embedded section. The deformation for modeling representative element of pile was developed. The pile-soil interaction under lateral load was considered through group pile p-y curves method. The pile-soil interaction under vertical load was considered by using shear displacement method with the consideration of soil-pile relative slip and second order bending moment caused by vertical force ( ) effect. The load-displacement relationship and bending moment distribution can be obtained by iterative method. The accuracy and reliability of the theoretical calculation established in this paper were verified through comparing with previous results. The results expand the theoretical calculation method of pile foundation under oblique load, and provide a reference for related engineering design and calculation.

Uniaxial compressive strength of rocks is widely used in geotechnical engineering, as it can be directly estimated using relatively straightforward and cost-effective methods. In the present study, an empirical equation to predict the uniaxial compressive strength for anisotropic rocks is developed. The proposed equation has been used to fit the data for four types of anisotropic rocks, i.e. sandstone, phyllite, slate and shale. Three different statistical parameters (regression R-square value R2, relative error Dp and average absolute relative error AAREP) have been used to assess the predictive ability of the empirical equation. Results show that the predicted uniaxial compressive strength values agree well with the experimental values. Statistical evaluation of performance of the proposed expression has also been carried out using a uniaxial compressive strength database, which includes 274 uniaxial compressive tests conducted worldwide on anisotropic rocks. Further, predictive capabilities of the proposed method have been compared with those of three commonly employed methods. Statistical analysis result shows that it is possible to predict uniaxial compressive strength of anisotropic rocks even if three data of uniaxial compressive strength tests at orientation angle ? 0°, 30°and 90°are available.

A model test for piles located in steep slopes has been conducted based on similarity theory. The transfer of axial loading, and the identification of critical buckling load have been investigated. The theory calculation formula and the fitting formula of critical buckling loads were obtained. The results show that there is no obvious inflection in the relationship between load and displacement. The buckling failure mode is thus dominant. Further, larger vertical and horizontal displacements of the pile top is observed in long piles. The critical buckling load simultaneously depends on the vertical and horizontal displacements of the pile top. In addition, the larger inclination the slope or the longer the free section of the pile result in smaller critical buckling load, and smaller vertical bearing reduction coefficient.. The comparisons shows that the result from the theoretical calculation and the fitting formula both agree with the result of model tests, and the maximum error is less than 10%. The rationality of the model tests, the calculation theory and the fitting formula is verified. These can provide references for the practical engineering design

Particle breakage can occurs within railway ballast under relatively lower confining pressure, resulting in a change in the particle gradation. Gradation significantly influences the physical and mechanical characteristics of ballast. There is an increasingly urgent need for constitutive modeling of ballast for the prediction of gradation evolution under loading conditions. Based on the triaxial test results of ballast, a boundary surface model for ballast under relatively lower confining pressure is developed by employing the fractal breakage index defined by Einav and the theory of boundary surface plasticity. By the comparisons of experimental results, it is shown that the proposed model can well indicate the stress-strain behavior of coarse aggregate under low confining pressure, and provides a reliable prediction of gradation evolution caused by particle breakage during loading.

The determination of lateral force capacity of piles is a problem to be solved in construction of soft soil area. Based on the Matlock p-y curve used in soft clay, a simplified double broken line model of Matlock p-y curve was proposed, and then the undrained shear strength index su and CPT cone tip resistance qc were used to represent the model parameter kini and pu . The dimensionless relative stiffness coefficient of pile and soil, noted as KR, was used as a classification standard to differentiate rigid pile and flexible pile. The relationships between the initial tangent modulus coefficient denoted KE and the horizontal soil resistance coefficient denoted KC were established. At last, the displacement standards for lateral capacity of rigid pile and flexible pile in soft soil foundation were developed. Results show that the displacement control standards can quickly determine the pile critical lateral capacity. it demonstrates a practical and reliable method of evaluating lateral capacity of pile foundation.

To study the detrimental impact of one-side surcharge load on existing piles, the force and displacement characteristics of bridge piles and piers subjected to embankment load on soft ground is discussed through an accident of bridge piles-and-piers deviation on an express highway, Zhangjiagang. According to different boundary conditions of the vertical pile-pier of existing bridge, the pile-pier applied by a side embankment load is divided into free segment, passive segment and active segment. By considering the yield of soil and the constrained boundary influence of upper structure, differential equations of bridge pile-pier are derived using tri-parameter model. A semi-analytical solution of the behaviors and deformation of bridge pile-pier is obtained using matrix transfer method. By checking calculation of the lateral deformation and bending moment of bridge pile-pier in the accident example, the applicability of the proposed solution is verified. The factors which affect the calculation results, such as the length of pile discrete element and the depth of pile passive segment, are also analyzed in the actual calculation example. The proposed method can give reference for the calculation of the response of passive piles adjacent to one side load.

This study is to improve the theory of overlying strata response and control during typical shallow coal seam longwall mining. A total of 22616 working face of Shendong coalfield was taken as an example. Similarity simulation experiment, theoretical analysis and field application were used to investigate the fracture characteristics of the overlying main roof and the load transfer effect of sandy soil stratum during the typical shallow buried coal seam longwall mining. A new method was proposed for calculating the supporting force in the period of roof weighing of the shallow stope, and it was further applied to determine the working resistance of support on site. Research results show that at the moment of the instability of the breaking main roof sliding, the dynamic loading occurr violently and the bench of overlying strata subsides obviously. The friction between sandy soil column leads to a certain transfer effect on the surface sand load but not its total self-weight acting on the bedrock. Hence, the load transfer effect of sandy soil stratum and the conditions of bedrock weight were taken into full account in this study. The rock column method was introduced to correct the classical mechanics model parameters of the main roof structure. Moreover, mathematical models of roof supporting force were improved during weighting in the shallow stope. Results show that the maximum working resistance of support is 10 506.8 kN per support during the first weighting of stope roof and the value is 7 475.26 kN per support during periodic weighting. It is proven that calculated results agree well with the field observation data. ZY11000/24/50 type hydraulic support is adopted to control the roof of stope, which perfectly meets the requirements of support force. Thus, both the safety and high-efficiency of mining in working face are well achieved. Therefore, this study provides important references for the determination and selection of the working resistance in the typical shallow coal seam of the longwall working face.

At present, determining the rock joint size is usually based on the joint trace length in exposed rock area, but the estimated results are often affected by the limited area of exposed rock mass. In this research, we try to estimate the rock mass size according to the joint characteristics around a borehole. At first, the joint and dip information in a geological drill is obtained through the borehole camera technology, a equation for joint plane is developed in the range of drilling depth. Based on this equation, the connectivity criterion among the joint surfaces is constructed and the joint surface trace length is determined; subsequently, the trace mean function of trace length. Finally, the size of rock joint is estimated according to the relationship between trace length and the rock mass size.This method is applied to the combined underground mining-ore dressing of Zhangjiawan iron ore, showing its reability and high accuracy.

In general, a certain value of acceleration is applied to the sliding mass when analyzing the seismic stability of landslides，which ignores the propagation of seismic wave during the process. However, the failure of a landslide in an earthquake is fundamentally caused by the occurrence of the acceleration difference between the sliding body and the sliding bed when seismic waves propagate in rock and soil. In this study, a formula was deduced to calculate the acceleration difference. Taken the Yushu airport road landslide III in Qinghai province as an example, the dynamic input was referred to the time history curve of acceleration recorded at the airport seismological observatory in Yushu earthquake. Meanwhile, the time history curve of the dynamic stability coefficient of the landslide was obtained by using the transfer coefficient method. The calculated results show that the stability coefficient of the landslide in natural state is 1.269, the minimum dynamic stability coefficient is 0.962, and the minimum average stability coefficient is 1.069. The above results indicate that the overall stability of landslide is good. Although the entire failure of landslide would not occur in an earthquake, some local deformation happens. It is also verified that the calculated results are consistent with the observed phenomenon after the earthquake.

The relationships between compression index Cc and physical parameters of soft soil have been studied by many researchers. However, a comprehensive summarization of all these empirical relationships is missing. Eight Empirical relationships of Cc with liquid limit, seven relationships of void ratio e0 and six relationships of natural water content wn from different regions in the world are summairized in this paper. It is found that these Cc-wn relationshps have very similair slopes (about 0.01). Therefore, a general relationship is proposed. The Cc-wn empirical relationships from different Chinese costal areas are compared, and some test data are also collected. It is shown that these Cc-wn relationships can be divided into two categories and their empirical relationships are presented repectively. Southern areas such as Guangzhou, Shenzhen have soils with smaller slope (about 0.008) which is close to the value of 0.01 of soils from foreign regions. Northern areas such as Tianjin, Shanghai, Lianyungang have soils with much larger slope (about 0.02). This difference may relate to the soil structure. This article also evaluates the influence of the soil disturbance on the Cc-wn statistical relationship and discusses the applicability of compression ratio CR with wn relationship provided by Lambe and Whitman for soft soils.

This study is to reveal internal relationships between cumulative damage effects of rock blasting and acoustic variation characters of rock mass. In this study, a small dose of blasting was conducted for ten times on the surrounding rock in underground engineering. Then in-situ acoustic measurement was carried out to analyze the corresponding damage of rock mass. Based on the fast Fourier transform (FFT), attenuation characteristics of the acoustic wave were discussed when propagating in rock mass with blasted damage. Meanwhile, this study also investigated the effect of blasting times on variation laws of acoustic parameters of rock mass, such as the dominant frequency and maximum amplitude in the frequency domain. In addition, the influence factors, for example, the thickness of the broken zone, the distance between transducers, the distance from the explosive source, were all analyzed as well. Research results show that high-frequency components of acoustic signals were absorbed gradually with increasing and extending blasting rock cracks, while the proportion of low-frequency components grew up constantly with the addition of blasting times. At the same time, the dominant frequency was shifted in the low-frequency direction. Furthermore, the distortion degree of frequency spectrum curves increased. It is found that both the dominant frequency ratio and the maximum amplitude ratio in the frequency domain declined nonlinearly. Moreover, the latter was more sensitive to blasting damage than the former. The variability of rock mass frequency spectrum became weakening with increasing the distance from the explosive source. The increase of the dominant frequency and the attenuation of the maximum amplitude in the frequency domain were substantially significant with the increase of the distance between transducers. Therefore, this study provides a valuable reference to enrich and improve the acoustic method for cumulative damage effects of rock mass blasting.

The strength property of the intermittent jointed rock mass is an important factor which affects the safety of large slope and tunnels. With the increasing degree of environmental degradation induced by the acid rain, pollution and other factors, it is necessary to study its influence on the mechanical properties of intermittent jointed rock mass. Based on the existing bond contact model, a novel bond contact model, in which the process of environmental degradation was simplified ultimately as the constantly dissolution of bond between the particles, was established and implemented into a commercial distinct element code. Then, a series of direct shear tests with different connectivity rates and normal stresses under various degree of environmental degradation was conducted in DEM. The results imply that there is a similar tendency of shear stress-displacement curves obtained from intermittent jointed rock mass samples with varying degree of environmental degradation. And with the increasing of environmental degradation degree, the main failure mode of intermittent jointed rock mass changes from tensile crack to shear crack. In addition, the initiation stress, the cohesion and internal friction angle of non-penetrating jointed rock mass are reduced with the increasing of environmental degradation degree.

Based on in-situ stress measurement and three-dimensional (3D) inversion computing model of Huangdeng large-scale underground cavern, this study is to revearl the distribution characteristics of in-situ stress fields and further to provide accurately initial material for the design of the underground excavation and reinforcement. The inversions of in-situ stress fields are obtained by the multiple linear regression (MLR), the artificial neural network (ANN) and the stepwise linear regression (SLR) combined with ANN, respectively. Moreover, the SLR-ANN method is characterized by the nonlinear intelligent inversion analysis, which especially considers the geological history process. In addition, the results of inversion analysis are proofread and examined with measured in-situ stress results. It shows that the inversion results by these three methods are in good agreement with measured results. The results indicate that these three methods can truly reflect the distributions and characteristics of 3D in-situ stress in the whole underground cavern group. Compared with these three methods, the results by SLR-ANN algorithm are closest to measured results. This method also significantly improves the inversion efficiency by reducing inversion parameters. Therefore, it can be practically applied in realistic scenarios to achieve efficient and accurate estimations of in-situ stress in rock mass.

By simulating the sliding face with point contact, a numerical method for slope stability analysis with a prescribed sliding plane is proposed combining with the FEM and strength reduction theory. For a specific slope, the shear and normal forces of the sliding plane are represented by the forces of the shear and normal springs. Combined with the theory of strength reduction and the Mohr-Coulomb strength criterion, numerical results can be obtained by iteration of the spring stiffness under equilibrium condition. Compared with limit equilibrium method, the present method avoids the limits due to the slice-force assumption. Compared with shear strength reduction method in a finite element model, the present method overcomes the sliding piles and the convergence difficulty. The present method can provide body stress, boundary force and stability coefficient under limit state. The amplitude, direction and action point of the landslide thrust on an arbitrary section of the landslide, can also be obtained under a given safety factor. The present method, with strict theoretical basis, provides some guidance to landslide harness in practical engineering applications.

This study investigates the vertical vibration of pile in layered soil under transverse inertia of pile and effects of soil stress diffusion. In the model pile-soil system, Rayleigh-Love rod is applied to simulate the pile, and the soil at pile end is simplified as diffused fictitious soil pile model to reflect the supporting role of soil. Plane strain model is used to describe the interaction between the pile and soil around. Firstly, given the initial and boundary conditions, the dynamic response under half-sine exciting pulse on the pile top is obtained using integral transformation and the recursive method impedance function. A finite element model of the pile-soil system is established to carry out numerical calculation. Then the impact of related parameters, e.g., impulse width of exciting force, pile diameter, length of fictitious soil pile, and vertical interlayers in pile side soil are analyzed by numerical solution (ANSYS/LS-DYNA) and theoretical solution respectively under various working conditions. Finally, the feasibilities of the two solutions are mutually verified.

It has been a long concerned issue that a variety of measurement techniques is applied to detect the internal structure of underground medium in geotechnical engineering. The theoretical basis of the impact imaging method is to take characteristics of the elastic wave propagating through different medium surfaces. Thus, it has the substantial potential to produce the resolution for target medium and the feasibility for the detection of buried low-velocity layers. In this study, the principle of impacted image detection method was clarified. For the horizontal layered medium model with a low-speed interlayer, a series of response waveform data in each separate case was obtained by using finite difference numerical simulation. Then the corresponding amplitude, dominant frequency energy and time frequency of response waveform were analyzed. Furthermore, their change characteristics were obtained. In addition, the validity and the accuracy of the impacted image detection method were verified. Based on the results of numerical cases, the impact imaging method was applied to detect the grouting quality of the immersed tube tunnel in Haihe Binhai, Tianjin. According to the measurement of waveform data collected on-site, we investigated the visualization of the response waveform, frequency spectrum, time frequency and the comparison of the change characteristics of elastic wave before and after the filling. A comprehensive evaluation was finally realized for the grouting effect on the immersed tunnel baseboard and a satisfied detection result was also achieved.