Stability Analysis Of Soil Slope Considering Transient-Unsaturated Seepage And Dilatancy Of Soils

Slope stability problems, as one of the prime concerns of geotechnical engineering, are commonly encountered in these projects, such as natural soil slopes, excavated slopes, road subgrades, embankments, earth dams, and so on. It is too difficult to determine definitely the safety factor of soil slopes subjected to the fluctuation of water level or rainfall. Dilatancy of soils has an influence on the shear strength of soils, but it is considered cursorily in the stability of soil slopes in practice, which leads to certain difficulty in estimating the stability of soil slope correctly. In this thesis, the stability of soil slope subjected to unsaturated transient seepage induced by the fluctuation of water level or rainfall is discussed in detail. And how to consider reasonably the dilatancy of soils in the analysis of slope stability and its influence on the stability analysis of soil slope is studied either. Results of this research are of great significance both in theory and application to engineering. The research work done is presented as follows:1. To establish a double-hardening constitutive model which is suitable for different initial density sands, based on the critical state and state-dependent dilatancy theories. One set of model constants can simulate well the stress-strain responses of a single sand under different confining pressures and different densities. This model can investigate the dilatancy behavior of sand well. This constitutive model is verified by the triaxial compression test results of Toyoura sand and Hostun sand, the good predictions show the rationality and validity of this model. The numerical integration methods of the three-dimensional stress space and triaxial test conditions are derived, and the contrast analysis of different numerical integration methods taking Toyoura sand as the example is carried out.2. The continuity equations of transient unsaturated seepage are analyzed by two different methods; Limit equilibrium method used in the stability analysis of soil slopes subjected to transient unsaturated seepage induced by rapid drawdown is discussed in detail. The influence of the unsaturated characteristic on the slope stability is investigated, including the influence of the unsaturated characteristic on the effective stress distributing along the slip surface, the influence of the unit weigth of soil above phreatic line, the influence of matric suction on the shear strength. The influence of these factors on the slope stability subjected to rapid drawdown of water level is analyzed through some examples, it is important to determine reasonably the distribution of pore water pressure and the position of phreatic line for the results, the primary analysis is conducted on the effect of transient seepage by rainfall infiltration on stability factor further.