| There is a zone of frequent geological hazard of landslide in the Three Gorges reservoir regions. When the reservoir is in operation in 2003, the rising of reservoir water level from 135m to 175m will lead to the submerging of part or whole of the landslides. It is a new and important subject for the operation of the Three Gorges reservoir that the stability of landslide will be influenced by the seepage flow resulting from the drawdown of the reservoir. The seepage flow of landslide and the stability evaluation are a complicated theoretical and application subject.On basis of the analysis of the engineering geological characters of landslide in the Three Gorges reservoir regions, the classification of landslides is made suitable to analyze landslide stability by seepage flow. The seepage flow theory for fractured rock masses is applied to the study of the seepage flow of landslide and Monte-Carlo method is used to study the fracture character. The theory of limit equilibrium of rigid body and the numerical simulation of finite element are applied to the research on the evaluation of stability for landslide caused by the seepage flow. The main achievements are as following:1. Through the research on the engineering geological characters of landslide in the Three Gorges reservoir regions, the influence of the geological and natural environment factors upon the development of landslide, and the sensitivity of stratum, structure and rainstorm factors to the development of landslide were discussed in detail. According to the results, the general engineering geology model and the seepage flow models of landslides which are classified by lithology, space location and fracture character in the Three Gorges reservoir regions were established, which offer a new ideal for the stability evaluation of landslide by seepage flow.2. In the condition of the landslide with whole body, Monte-Carlo method, by which discontinuities network in rock is simulated, is the main way of the study on geometry features of landslide fissures. By this method, the preponderant discontinuities of landslide rock masses, network graph and connected graph of discontinuities have been gotten and the permeability tensor of the discontinuities network has been obtained. 3. According to fracture character of landslide, three kinds of seepage flow models for the bedrock landslide have been established and its adaptability has been discussed. The models include: the discrete network model, the equivalent continuum media model and the double porosity medium model. It is valid to establish the equivalent continuum media model for these landslides in condition of high dense fracture and wide area, The permeability tensor of the discontinuities network has been solved by Monte-Carlo method and the seepage flow equation by the finite element. Based on the theory of fracture seepage flow and the deformation constitutive relations, the couplings of seepage field and stress field have been analyzed.4. The graph theory in the discrete mathematics has been applied to the research on the connectivity of fissure networks and the qualitative description and geometry graph have been defined by mathematic express, the express of numerical matrix. Based on Wittke discrete modeland the singular fissure cube theory, the node flux conservation equation, the loop pressure conservation equation and the bar unit water pressure equation have been established. This model shows its efficiency in condition of sparseness landslide fissure or a small area landslide and the geometry feature of landslide fissure ascertained and it provides a new way for the research of landslide seepage.It's hard to establish the model of every fissure in whole seepage zone for computer simulation when the fractures are very dense. In this case, the main fissures network must be classified and the small fissures should be expressed by the method of permeability tensor. The satisfying results can be attained by establishing the seepage flow equation of main fissures network an...
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