Applied Mechanics and Materials Vols. 170-173

Abstract: A lot of data indicates that rainfall has always played the very important role in landslide triggering. The paper discusses rainfall as a dynamic parameter in term of the load/unload response ratio theory, using the Xintan landslide as a case study. Analysis of the available data indicates that the occurrences of landslides in this region are controlled by rainfall, whose intensity and rainfall processes are the most important dynamic factors in determining the stability of slopes. Therefore, the relationship between rainfall and the movement of typical landslides has been specifically analyzed for the Xintan landslides by using the loading/unloading response ratio parameter of rainfall. The result of this study indicates that the mutation of the loading/unloading response ratio of rainfall of the Xintan landslide in the Three Gorges Reservoir regions, China occurred just before their destabilization, which shows that the loading/unloading response ratio of rainfall and its changing feature can be taken as a precursor for the landslides induced by rainfall.

Abstract: Currently the study of soil’s horizontal displacement caused by foundation pit excavation is still deficient. Based on existing research material, this paper builds the displacement models of soil’s horizontal displacement. Through adopting three-dimensional finite difference method, working process and related influencing factors are simplified into displacement boundary condition which is applied to numerical model to analyze soil’s horizontal displacement. The conclusion can be used to estimate displacement of soil behind retaining wall, such as soil’s horizontal displacement and range of influence.

Abstract: Deep excavations in soft-clay layer on sloped bedrock often leads to lateral displacement on retaining structures and uneven settlement due to unbalanced pressure generated from excavation. A construction project for which an excavation was complete in soft clay layer on sloped bedrock in Taipei City was adopted in the study. It is learned from the observation logs of the studied case that a significant difference exists in the lateral displacement of diaphragm wall and settlement between up and down-slope sides of sloped bedrock. Deep excavation is in fact profoundly complicated interaction between excavation strutting and soil. In general practice, the design of excavation is frequently simplified as a 2D strain behavior. However, the actual excavation on sloped bedrock is quite different from 1D or 2D simulation in a symmetric manner. Therefore, 2D finite element analysis program, PLAXIS, is introduced for the analysis on the behaviors of soil clay layer on sloped bedrock in excavation. The result is compared with onsite observation data, including displacement of retaining wall, settlement, axial loads of struts and others. The result of retaining wall displacement analysis is found consistent with the trend derived from onsite observation, which is possible for reference of similar engineering analyses and designs in the future.

Abstract: Tunnel engineering information construction has been widely used, and the back analysis is its core. As the common useful method, displacement back analysis is of special advantages. This paper introduces the calculative method based on the application in a railway tunnel. The result shows that strain softening model can be used to simulate the large deformation mechanism of surrounding rock.

Abstract: The shear strength value of unsaturated loess is required in the design in geotechnical engineering in the North and the North West of China. In 2004, a new method, that is the fractal model theory, was proposed for determining the shear strength of unsaturated soil. Based upon the fractal model theory, the surface fractal dimension DS and the air entry value of two unsaturated loess samples are obtained from their soil-water characteristic curve (SWCC), the shear strength contribution due to matric suction of the two loess samples is determined, a new approach for determination of the shear strength of unsaturated loess with its SWCC is presented. By comparing results of this paper with those of the laboratory tests, the relationship between the SWCC and the shear strength of unsaturated loess is discussed and the validity of the fractal model theory for unsaturated loess is explained.

Abstract: This thesis introduces various factors of surrounding rock stability mechanism and instability modes, indicates its control methods and thought. The achievements apply well in engineering practices and have good values and researches on surrounding rock stability have instructive significance in engineering execution.

Abstract: In order to promote the experience of applying O-cell pile test to determine the behaviors of integral pile in Jinan, a case of O-cell pile test in Jinan was analyzed with proposed approach. The pile-soil system was simulated with FEM. The resistance parameters of piles, the load-displacement curves and the ultimate bearing capacity of integral pile were determined. Comparing with results obtained from load transfer method, it is found that the p-s curve of integral pile obtained from load transfer method is conservative.

Abstract: In accordance with equilibrium differential equations and compatibility conditions of deformation, the partial differential equation of induced stress is achieved for elastic surrounding rocks of tunnels and chambers of round section. By method of the superposition principle, elastic analytical solutions of induced stress of surrounding rocks is derived from the partial differential equation, which is based on stress functions and boundary conditions.

Abstract: Vacuum Tube Well Dewatering (VTWD) is one of high efficiency methods to vacuum dewatering in Beijing district in recent years. Water output, surrounding drawdown, and land settlement of vacuum and normal tube well respectively were measured during the process of engineering dewatering at three sites in Beijing subway engineering. The results showed that the water output by VTWD was 1.6 to 2 times than that by Normal Tube Well Dewatering (NTWD) while the land settlement was twice compared to NTWD. It is suggested to consider the carrying capacity of surrounding environment when using VTWD.