RESPONSE PATTERNS OF OLD LANDSLIDES WITH DIFFERENT SLIP-SURFACE SHAPES TRIGGERED BY FLUCTUATION OF RESERVOIR WATER LEVEL

Much of relevant materials of 463 old landslides which had significant deformation in Three Gorges Reservoir Area are collected from June 2003 to June 2015. This paper studies the evolution models and slip-surface shapes of some typical old landslides. It concludes that there are 4 typical slip-surface shapes of circular, polyline, rectilinear and chair shape. Results of macroscopic analysis of wading extent and deformation time distribution can be summarized as follows. (1) The hydrodynamic pressure has obvious effect on the stability of the circular and rectilinear slip-surface landslides. Most of these two types of landslides deform at the lowering stage of water level when the front or middle is waded, especially after the first time to the highest water level. (2) A small part of the rectilinear slip-surface landslides is deformed at the stage of low water level after the drop because of lags in response. (3) The deformation occurs in the chair-shaped and polygonal line slip-surface landslides at the increasing stage of water level owing to effect of buoyancy weight loss, especially to the first 135m and 175m storage. Most of the chair-shaped slip-surface landslides are deformed when the front is waded as well as the rear wading extent of the polygonal line slip-surface landslides is higher than other 3 types. At last, the research results have a certain reference meaning for wading old landslides prevention in Three Gorges Reservoir Area.