Study On Mechanism Of Landslides In Horizontal-strata In WanZhou, ChongQing City, Three-Gorges Reservoir

The second stage program of large geohazards control and prevention in the reservoir of Three-gorges has almost completed, and the third stage geohazard prevention program is going, WanZhou city is located in the middle of Three-Gorges reservoir. With the rapid enlargement of urban construction and the increasing of human activities in WanZhou area, many geohazards as rockfalls and landslides have been taken place again and again, which caused enormous losses. So the GuanTangKou landslide and HePing-square landslide in WanZhou have been classified four major landslides in the reservoir of Three-gorges.There are a lot of horizontal-strata landslides in WanZhou area, whose angles of inclination are about 3 to 5 degree. According to the view of mechanics, it is often hard for the horizontal strata landslides to slide because the component force of landslide's gravity along inclined slip surface is too small to push the landslide. So the horizontal strata landslides often appear in the specific geological environment. The horizontal strata landslides in WanZhou area appear in Mesozoic-Cenozoic clastic rocks, the sandstone and mudstone, which is a kind of special geological environment that causes horizontal strata landslides. If we explain the formation and mechanism of the horizontal strata landslides by only external factor as rainstorm, it is obviously discredited. In fact, it is found that the weak layer of expansive soil does great effect to the cause of horizontal strata landslides in WanZhou area. It seems very simple for the geological environment that horizontal strata landslides appear, but it is difficult to explain the reason why so horizontal strata landslides have come into being and is also difficult to explain the formation and mechanism of the horizontal strata landslides. So the formation environment, the course of development and the failure mode about the horizontal strata landslides are needed to study, which is very important for the control and prevention of the horizontal strata landslides in the reservoir of Three-gorges.This paper mainly discusses the following points:First: According to theories of elastic mechanics and Mohr-Coulomb rule, this paper quantitatively studies fissure water pressure, which causes landslides of horizontal strata in Three Gorges reservoir area. Author proposes the criterion of fissure water pressure, which causes landslides of gentle dip slop, then puts forward calculation method of critical depth of water when landslides of gentle dip slop failures. Furthermore, Author discusses the mechanism and course that the fissure water pressure causes slipping.Second: Have set up a experimental model that reflect the change of geological environment that the weak layer of expansive soil is located after human activities. By test of swelling pressure and expansion rate with cutting ring sample under different pressure, it is found that restrained pressure has obvious influence on expansive soil's expansibility: the greater restrained...