Study On The Influence Of Rainfall On Landslide Process

The two ways are mainly used to study the laws of landslides caused by rainfall. First, to explore the relationship laws of rainfall and landslides through statistical analysis; second, to make a detailed research on the physical process of landslide caused by rainfall seepage as well as to establish the quantitatively analytical model.The author of the thesis considers that although some achievements have been made in the relation of landslides and rainfall at home and abroad, there are still some blanks in the combination of regional statistics study and mechanism research. With the reference to mechanism research, many researchers haven't really touched the one-time rainfall process, rather devised certain assumption conditions, such as fixed flux boundary conditions and bedrock surfaces parallel to natured slope surface, etc.With regard to the stability influence of landslide caused by rainfall, the emphasis should be put on calculating the transient seeping field brought about by rainfall infiltration, with which we can calculate the real-time stability variation of landslide on the mature limit equilibrium method. This paper firstly uses statistics analysis method to analyze the relationship between macroscopic area landslides with rainfall, and makes sure some pre-warning rainfall threshold valve values of landslide. On the basis of summarizing the research findings of our predecessors, the research train of thought of Wu Hongwei in particular, through the simple governed equation of non-coupling unsaturated seepage, and combined with rainfall conditions of macroscopic statistical analysis, the paper evaluated the two-dimensional values of transient seepage field according to the variation of rainfall, rainfall strength , duration time for the landslide, thus realtime dynamic safety factors during rainfall process are acquired.The main research contents are as follows:1. Adopting statistics analyses method to analyze the relationship of Zhejiang province's rainfall with region landslides in Zhejiang, then the article discusses the model of effective rainfall.2. The paper makes sure the macroscopic region landslide's critical rainfall and the rain intensity threshold valve values of landslides in Zhejiang province, and divides the early-warning grades of landslide disasters of the study areas into three-grades.3. The paper deduces saturated and unsaturated seepage basic differential equations, and expatiates the basic concepts of saturated and unsaturated seepage.4. Making use of existed two dimension unsaturated seepage analyses software to simulate the transient seepage distribution during the different rain conditions (rainfall strength, rainfall,rainfall duration time, rain type), then the article calculates the water pressure of seepage and the real-time stability coefficients of the landslides by the limited equity method. The main research results are as follows:1. The biggest relative coefficient is between big rainstorm and landslide, next in order for rainstorm and heavy rain. The relation shows that big rainstorm and rainstorm greatly influence landslide disaster, and can directly cause the occurrence of landslide. During the inquisitional landslides, a great deal of landslides occurred within big rainstorm or rainstorm or after them.2. The paper makes sure the model of the effective rainfall that rainfall coefficient a =0.8 acts as the effective rainfall coefficient for non-typhoon area,a =0.7 acts as the effective rainfall coefficient for typhoon area.3. The paper makes sure the macroscopic region landslide's critical rainfall and the rain intensity threshold valve values, and superposes the risk grades of rainfall with the easy-occurring grades of landslide disaster, dividing the early-warning grades of landslide disasters of the study areas into three-grades, namely, not early-warning area, first early-warning area and early-warning area.4. The numerical simulation results show that the influence of stability coefficient is small in 50mm/d rainfall, bigger in 200mm/d rainfall and in 250mm/...