某水库岩质高切坡在降雨及施工条件下的稳定性及破坏规律研究

Stability and Failure Law of Rock High Cut Slope of A Reservoir under Rainfall and Construction Conditions

为研究岩质高切坡在不同施工期和运行期条件下的稳定性问题,以某水库溢洪道进口段开挖高切坡为研究对象,在充分分析其地层岩性分层和结构面性状的基础上,开展人工开挖高切坡的结构面组合特征、失稳方式和不同施工状态下的稳定性研究。研究发现:边坡上部层积部分各结构面间组合交线均与边坡倾向相反,属于对边坡稳定性有利的结构面组合,整体较为稳定;下部花岗岩部分层间挤压带(1)、(2)受陡倾角节理组(4)、(5)的切割,可能使边坡局部发生小规模楔体滑动破坏;稳定性分析结果表明边坡开挖前基础基本稳定性状态(F_(s)=1.3),按设计坡比开挖后高切坡稳定性欠佳(F_(s)=1.0~1.1),受不良因素诱发贯通屈服面的风险较大,针对潜在不利结构面采取1000 kN和2000 kN预应力锚索加固后边坡稳定性系数F增加至1.5,坡脚最大压应力20 MPa,在允许的强度范围以内。

For the study of rock cut high slope under the condition of different construction period and operation period of stability problem,this article is based on a reservoir spillway import excavation high cut slope as the research object,in full analysis of the formation lithology hierarchical structure and surface properties,on the basis of high cut slopes in artificial excavation,buckling mode combinations of structural plane and the study of stability of different construction conditions.The results show that the intersecting lines of the structural planes in the stratified part of the upper slope are all opposite to the slope inclination,which is a combination of structural planes favorable to the stability of the slope,and the overall stability is relatively stable.In the lower part of the granite interlayer extrusion zone(1)and(2)cut by the steeply inclined joint group(4)and(5),small wedge sliding failure may occur locally on the slope.The stability analysis results show that the basic stability state of the foundation before slope excavation(F_(s)=1.3),and the stability of the high-cut slope after excavation according to the design slope ratio is poor(F_(s)=1.0-1.1),and the risk of inducing the penetration yield surface by adverse factors is large.The slope stability coefficient Fis increased to 1.5 and the maximum compressive stress at the foot of the slope is 20 MPa,within the permissible strength range,after 1000 kN and 2000 kN prestressed anchor cables are used to strengthen the potentially unfavorable structural surface.