Fully Coupling Analysis Of Seepage And Stress For Compound Soil Nail Support Technology Based On GO-SLOPE

Compound soil nails support technology for deep excavation has got more and more application because of its many advantages, such as easy and rapid to implement, safe and less investment. The new support technology with a wider field of application and prospects remedied the shortcomings of traditional soil nails support, can meet the requirements of current foundation pit design. However, there are some disputes, such as its design. In this thesis the exact seepage and stress of surrounding soil FEM computational model is applied to analyze the behavior of compound soil nails in non-saturate and saturate soil. Extensive computations are carried out to further reveal the behaviors of soil-nailing and to provide scientific basis for its broad application and optimum design. Does in at present in this kind of research, considered the water the influence and the non- saturated soil suction influence finite element computation model is also unusual. The main contents are as follows:1. Introduce the compound soil nail supports and protects the technology and its the characteristic, the development survey, the application prospect; summarize common composite soil nails support form and analyze its role mechanisms.2. Discuss the method and the way of the optimized design of the compound soil nail support, from the variables and computation model study the optimized design. On the basis of predecessor propose some beneficial conclusions for the design; Studied the influence to slope stability at the computational method, the computation considered the pore-water pressure and the computation consider the suction, which can provide the basis for optimum design of support structures and the model establishment.3. Take the pore-water pressure and the displacement as the variable to establish seepage and stress of surrounding soil complete coupling finite element computation model. In themodel the reciprocity between the support structures, the water and the soil, the soil non-linear performance and the penetration coefficient nonlinearities, are considered. Simulate excavate process, promptly adjusts the design proposal according to the computed result, achieved the optimized design, obtains directly the safety coefficient.4. As an engineering case, seepage and stability analysis of foundation pit in Beijing province in normal work process is finally computed by Slope/W, Sigma/W and Seep/W with and without the fully coupling model , respectively, and in the analysis based on the probability and the statistical theory, use Monte - Carlo law to consider the changeability and uncertainty . The work performance of support structures, like the nail internal force distribution, the stress field change and the structure distortion characteristic and so on, is discussed on the basis of the simulation results.It is conclusions that: (1) to explore thoroughly the action mechanism and the destruction mechanism of support structure, seepage and suction must be consider; (2) the compound soil nail and the plain soil nail action mechanism is different: maximum tensile stress within soil nailing is more close sheet pile; destruction is not necessarily the whole tilt destruction, the sheet pile is destroyed possibly by the shearing failure also; The critical slip surface is relative to the support structure, unnecessarily through the toe of slope; The soil nail spacing, the density and the sheet pile inlay the depth affect the maximum horizontal displacement position, but not affect nearly to the pit bottom maximum subsidence position;(3) the coupling computed result indicate its soil body horizontal departure and surface subsidence are bigger than without coupling as a result of the hydrodynamic pressure function.