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Most landslides induced by reservoir impoundment and rainfall in the Three Gorges Reservoir area of China are usually characterized by bedding-plane shear zones. This paper presents an experimental study of the interaction between water and shear-zone materials. A series of tests, including wetting-drying cycles and soaking tests, were carried out. The results show that the fluid-solid interaction not only reduces the shear strength of shear-zone soil but also accelerates the disintegration process of clastic rock from shear zone. After the fluid-solid interaction at different pH values, the clastic rock samples produce the most clay minerals in acidic solution. Similarly, the clay minerals of shear-zone soil samples increase dramatically after 45 days of soaking in acidic environment. According to the tests, it is found that the shear-zone soil in eluvium may originate from the weathered clastic rock near the shear zones under long-term fluid-solid interaction.

Most deep-seated landslides are characterized by large volumes with deep shear surfaces. They are sensitive to hydrological forcing, especially in climate change scenarios. This paper studies the role of soil–water interaction in affecting the motion of a deep-seated landslide near the southeast coast of China, where seasonal rainfall combined with annual typhoons caused the instability of a previous stable slope. A comprehensive investigation consisting of field monitoring and experiments of soil–water interaction is carried out. The monitoring data show that the landslide exhibits alternate dormant and active stages, corresponding to rainy and dry seasons, respectively. The enduring precipitations predominate the landslide motion, while intensive rainfall brought by typhoon events leads to transient deformation. In addition, wet treatment of intact and reconstituted soils is adopted to mimic the interaction between rainwater and landslide material. The results obtained from in-situ and laboratory direct shear tests indicate that the soil–water interaction is time-dependent. The long-term interaction gives rise to significant strength reduction of soils, thereby regulating the movement of the landslide.

The objective was to analyse the water absorption and weakening of a Silurian argillite taken from the northwest of Hubei Province, China. Some experiments were conducted including measurement of the change in water absorption, the microstructure of the minerals, the porosity, and the strength of argillite samples, at different water absorptions, by scanning electron microscope, powder X-ray diffraction analysis, and needle penetration test. The results indicate that argillite was soaked in water for up to 0.5 days, water absorption rates were fast and the amount absorbed was large. At the same time, the rate of strength decrease was high and significant loss of strength was observed. Argillite soaked in water for 0.5 to 180 days had an increased water absorption at a slower rate, and the strength tended to be stable over time. The relationship between strength and water absorption was established: the strength decreases in the form of negative exponential function with increasing water absorption. Finally, the micro-mechanical model shows that, the decrease of attractive force of mineral grains and the increase in the force acting between mineral grains and the pore water are the main reason why this degree of water-weakening appeared in the argillite.

The stability of high rock slopes has become a key engineering geological problem in the construction of important projects in mountainous areas. The original slope stability probability classification (SSPC) system, presented by Hack, has made obvious progress and been widely used in rock slope stability analysis. However, the selection and determination of some evaluation indexes in the original SSPC method are usually subjective, such as intact rock strength and weathering degree. In this study, the SSPC method based on geological data obtained in the prospecting tunnels was presented and applied. According to the field survey and exploration of the prospecting tunnels, the weathering degree of the slope rock mass was evaluated. The empirical equation for the maximum stable height of the slope was applied to the slope stability evaluation in the presented SSPC method. Then, the slope stability probability of numerous cutting slopes in the sandstone unit was evaluated using the presented system. Results of the Geostudio software based on the limited equilibrium analysis of the investigated slopes were compared with the results obtained by the SSPC method. The results indicate that the SSPC method is a useful tool for the stability prediction of high and steep rock slopes.

A new geotechnical in situ test technique using a self-boring in situ shear pressuremeter (SBISP) is developed to evaluate the initial state (horizontal at rest pressure Ph), deformation (yield pressure Pf and pressuremeter modulus EP) and strength characteristics (cohesion C and internal friction angle φ) of soil. The SBISP possesses a self-boring drilling functionality that can greatly reduce the disturbance of the tested soil. The multistage compound loading method, which applies normal stress incrementally to the soil in the test hole while repeatedly applying shear stress, was adopted. Relying on the investigation of the cross-sea traffic engineering of Dalian Bay, three sites in the sea area of Dalian Bay were selected for SBISP testing of clay. The field vane shear test (FVT), pressuremeter test (PMT) and unconsolidated-undrained triaxial compression test (UU) were also evaluated at each testing site to compare with the SBISP test. The results measured by the SBISP and comparative tests (FVT, PMT and UU) showed the same trends with an increase in depth and change in strata. The differences in the test results were discussed in terms of the disturbance effect, anisotropy of undrained shear strength, differences in loading methods and instrumentation used in the different tests. A comparison between the results measured by the SBISP and in comparative tests shows that the engineering characteristics of Dalian Bay clay evaluated by SBISP are fairly accurate and can provide reference for the investigation and design of the cross-sea traffic engineering of Dalian Bay.

The displacement of pipe-soil contact points in the radial direction and the wedging effect of surrounding soil on the pipe perimeter during pipe pulling-back may have a substantial effect on predicting pulling forces for horizontal directional drilling installations. However, the influence of pipe-soil interaction on pulling force predictions is not considered in existing methods to predict the required pulling force. This paper provides a model representing the interaction between pipe and borehole. The mechanical characteristics of the pipe-soil interaction were numerically investigated with program ANSYS. Two parameters, the wedging coefficient and pipe displacement, were defined and associated parametric studies were performed to analyze the influences of relative factors based on a Yangtze River crossing project. The wedging coefficient is shown to increase with external load and ovality of the borehole, and decrease with increasing over-cut ratio, Poisson’s ratio and elastic modulus of soil. It can improve the prediction accuracy to consider the wedging effect since the difference among predicted results caused by wedging effect can differ up to 7.7% in example analysis.

It is reasonable to study the destruction and preservation of stone relics from a geo-environmental point of view. The Tongtianyan Grottoes, known as “the First Grottoes in Southern China”, are located in the city of Ganzhou, Jiangxi province, China, and are the largest cave temples in eastern China and southern China. The grottoes were carved into sandstone palisades during the period from the late Tang Dynasty (755–763 AD) to the Republic of China (1912–1949 AD). In China, the Danxia landform is a special landform characterized by red sandstone cliffs. Different from the grottoes located in arid climate regions, the Tongtianyan Grottoes have the lowest latitude (25°45′N) among all the grottoes in China, and the stone relics are under a perennially warm and humid environment. The monuments have suffered from various forms of weathering deterioration, which can be summarized as five types: exfoliation, bio-weathering deterioration, crack, erosion, and loss. Detailed investigations have been conducted to analyze the mechanisms of the weathering deterioration of the stone relics based on different aspects of geo-environmental characteristics. The weathering sandstone samples were analyzed using X-ray diffraction and X-ray fluorescence, and the chemical weathering indices (LOI, WPI, and WI) were calculated. We found that there is a boundary zone at a depth of 10 ± 2.5 mm from the surface to the inner rock based on the curves of the chemical weathering indices, and the rock outside of the boundary zone has much stronger weathering than that inside.

The objective of this study was to investigate the mechanical and anisotropic characteristics of slates in Northwest Hubei of China. For this purpose, uniaxial compression test and Brazilian splitting test were carried out on Silurian silty slates so as to analyse the mechanical and anisotropic characteristics as well as deformation and failure modes of slates under different loads. Meanwhile, the mechanical mechanisms of different failure modes were revealed. Research results showed that bedding planes in silty slates are the weak planes influencing the mechanical behaviours of rock masses so that silty slates present obvious anisotropy. Under uniaxial compression conditions, silty slates were more easily to be deformed more remarkably in the direction perpendicular to bedding planes in comparison with those in the direction parallel to bedding planes. When loads were applied along bedding planes, it was found that the specimens suffered from vertical splitting tension failure, which was essentially the instability of compression members; when the loading direction was perpendicular to bedding planes, splitting shear failure cutting through bedding planes occurred to specimens. The mechanical parameters measured also presented apparent anisotropy. Under the effect of splitting loads, silty slates were primarily subjected to tension splitting failure and shear failure along bedding planes. The measured tensile strength was shown to be the maximum in the direction parallel to bedding planes, while that perpendicular to bedding planes was the minimum. However, both the tensile strengths in these two directions were less than the compressive strengths. The tensile strength among the bedding planes was so low that tension splitting or shear failure easily happened along bedding planes when the splitting loads applied formed a small angle with bedding planes. Therefore, tensile failure among bedding planes and tensile-shear failure along the bedding plane are supposed to be avoided in practical engineering. This study provides a theoretical basis and technological base for the protection and treatment of rock slopes and other rock engineering design and construction in silty slate regions.

The objective of this study was to investigate the deformation and failure mechanism of silty slates loaded with an angle 0 and 90° between foliation and direction of uniaxial force. For this purpose, mineral composition and microstructure test, uniaxial compression test , acoustic emission (AE) monitoring and scanning electron microscope (SEM) were carried out on Silurian silty slates. Based on the results of tests to analyze the deformation and failure mechanism as well as the macroscopic failure modes, microscopic rupture surface characteristics and acoustic emission characteristics of silty slates under different test conditions. Tests results showed that the silty slates are mainly composed of clay minerals (chlorite and illite) and brittle minerals (quartz and feldspar) and in a layered structure. Under the two angles, silty slates specimens exhibited large differences in the deformation and damage process, macroscopic failure modes, microscopic rupture surface characteristics, deformation and failure mechanism. Besides, there are large differences in the relative parameters of AE event. These results reveal that there is a certain relationship between mechanisms of microscopic fractures and macro failure of silty slates.

A Shanshucao landslide, large displacement landslide, took place on 2 September 2014, at 13:19 in Zigui County, Hubei Province, central China, which was about 42 km from the Three Gorges Dam. It was located on the left bank of Luogudong River, which was a secondary tributary of the Yangtze River. Just as the well-known Qianjiangping landslide, this landslide was considered to be one of the longest displacement consequent slope failures, which was characterized by red layer rock landslide. This event has become an outstanding and valuable reference for landslide study and is of particular importance for understanding the influence of the stability of the slope in the Three Gorges Reservoir Area. The geomorphological and geological conditions of the landslide were investigated to identify and characterize previously discontinuous and slide stratum bed. The hydrogeological and geomechanical features were also analyzed. It was found that the landslide was triggered by both the long and heavy rainfall and the rising water level of the reservoir at high speed.

Shenzhen Universiade Center is located in Longgang District, Shenzhen city, Guangdong province. There are various size karst cave and soil cave on site and their buried depth are from 2m to 50m. With the application of GIS technology and statistical techniques, three assessment models were established to karst spatial distribution of Shenzhen Universiade Center. Model I was the Logistic model based on geophysical information with dependent variables as anomalous areas revealed by geophysical prospecting. Model II was the Logistic model based on drilling information with dependent variables as karst caves and soil caves revealed by drilling. The independent variables of both models were the geological factors affecting karst susceptibility, including lithology, groundwater depth and the distance away from tectonic lines. Model III was the Bayesian model with integrated information of Model I and Model II. The correct probability of the model I is 58.17% when karst occurs; when does not occur karst, the correct probability is 86.75%. The fitness rate is 90.75%. The correct probability of the model II is 60.34% when karst occurs; when does not occur karst, the correct probability is 79.13%. The fitness rate is 88.38%. The result shows that Bayesian model can establish integrated assessment model including multi- source data to a certain extent, which can be employed in karst susceptibility assessment. The results of Logistic model and Bayesian model can be used as evidence for karst ground collapse vulnerability in the site.

The deformation of the borehole and the chocking (wedging) effect of surrounding soil on the pipe perimeter during the pull back phase may have a substantial effect on pulling force predictions for horizontal directional drilling (HDD) projects. However, this effect is not considered in existing methods for estimating the required pulling force. This paper provides a model representing the interaction between the pipe and soil, for which the soil is assumed to behave as a Winkler foundation. The stiffness matrix of a plane rigid-frame element considering such interaction was derived by variational calculus and the principle of minimum total potential energy. Moreover, a nonlinear analysis of the interaction model was conducted using the finite element method. The pipe displacement and chocking effect were investigated considering the pipe-soil interaction, and associated parametric studies were performed to determine the relative importance of the various factors. Pipe displacement is shown to increase with load and over-cut ratio, but to decrease with increasing oblateness of the borehole and modulus of foundation (subgrade) support. The chocking effect is shown to increase with load and oblateness, and decrease with increasing over-cut ratio and coefficient of degree of subgrade support. In addition, both the pipe displacement and chocking effect for an elliptical borehole are greater than for the circular borehole, under the same conditions. © 2013 American Society of Civil Engineers.