STABILITY ANALYSIS OF RESERVOIR LANDSLIDE UNDERRAINFALL AND RESERVOIR WATERLEVEL DRAWDOWN CONDITIONS

摘要

After the Three Gorges reservoir is built, the reservoir water level will fluctuate between 175m and 145m because ofrnthe need of flood prevention and power generation. The periodical rise and descent of water level in high frequency and the influencernof heavy rainfall will change the intrinsic geological circumstance and conditions greatly which may result in the instability ofrnreservoir banks and slopes. Take a landslide locating in Zhongba reservoir bank as an example, according to the Three Gorgesrnreservoir water level operation options, considering the influence of the practical rainfall intensity-duration course in the ThreernGorges reservoir region, transient seepage influenced by the combination of the descending of reservoir water level from 175m torn145m and rainfall infiltration is calculated using the nonsteady fluid flow finite difference method ( FDM ) by which the changes ofrnrainfall and reservoir level can be considered day by day. The transient nodal point head (infiltration lines) are then used for limitrnequilibrium analysis of landslide. The change laws of landslide stability are discussed under different calculation conditions. Thernresults of stability analysis show that when the reservoir water level drawdown only, the coefficient of safety declines firstly, and thenrnincreases. There is a minimum safety coefficient when the reservoir level is at about 160m to 163m. In addition, when influenced byrnthe combination of rainfall and reservoir water level drawdown, the safety coefficient of landslide will decrease all the time till thernlandslide revives, the critical reservoir water level is also at between 160m to 163m , which will need more attention in the treatmentrnproject of landslide in Three Gorges reservoir area.