小湾水电站饮水沟大规模倾倒破坏现象的工程地质研究

倾倒破坏是陡倾层状岩体一类主要的变形破坏形式,一般发育于地表临空面附近的坡体浅部。根据文献资料,前人研究的倾倒破坏体能保持其完整形态者规模并不大。小湾水电站左岸坝前高边坡由于其特殊地形地貌及其岩体结构条件,使得如此大规模的倾倒变形体能保持其完整形态至今。由于倾倒变形体紧邻大坝且地势较高,一旦失稳,将给小湾水电站的建设造成不可估量的损失。查明倾倒破坏堆积体规模及其岩体结构特征,为倾倒堆积体边坡支护方案选择及稳定性评价参数选取提供依据。更重要的是,揭示这类大规模的倾倒破坏表现特征及其形成条件,对认识复杂条件下岩石高边坡的变形破坏机理具有一定指导意义。本文通过细致的野外调查,揭示了一类发育深度较大的大规模倾倒变形破坏。通过对边坡的详细描述与记录,阐明了这类变形破坏发育的特征和空间展布,并对其形成机制作了简要的分析。

ENGINEERING GEOLOGICAL STUDY ON A LARGE-SCALE TOPPING DEFORMATION AT XIAOWAN HYDROPOWER STATION

Toppling failure is one of deformation and failure types of bedded rock mass with high dip angle.It usually develops near the ground surface.It is thought that only small-scale toppling deformation can be retained completely before.Owing to the special topographic feature and structure of rock mass,a large-scale intact toppling deformation body was found at present at Xiaowan Hydropower Station left bank slope front dam.The toppling deformation body is near to the damsite and shows higher terrain.Once the toppling deformation failures happen the loss will be disastrous for the construction of the Hydropower Station.The size and structure of the rock mass was found out so as to offer evidences for choice of support projects and evaluation of the slope stability.Based on the field investigation,we discovered that a large-scale toppling deformation occurred at the damsite,which was developed to a great depth of about 200m.In this paper,the deformation phenomena revealed by surface excavation and underground galleries were described in detail including variation of the dip angle and rock mass structure.In terms of these,a mechanical model of the slope deformation is established and its formation process is analyzed.