水电站大型地下洞室长期稳定性数值分析

Numerical analysis of the long-term stability of large-scale underground cavern of hydropower station

围岩的流变特性是影响地下洞室变形及长期稳定的重要因素。在长期荷载作用下岩体会发生流变现象,特别软弱夹层在较高应力作用下其流变特性更为显著。以某水电站大型地下洞室为例,针对该地下洞室附近围岩存在着软弱夹层,且有些软弱夹层与开挖的洞室相互交汇,基于大型岩土工程分析软件FLAC3D,采用黏弹塑性流变本构模型(Cvisc),模拟了地下洞室围岩的流变力学行为;根据主厂房顶拱位移变化率规律确定出了开挖洞室2次支护的时间,对比分析了瞬时弹塑性条件下与考虑流变特性条件下洞室开挖后围岩的位移变形、应力场及塑性区的分布。数值模拟结果表明,由于着软弱夹层的影响,洞室围岩发生较大的变形,特别是在开挖洞室与软弱夹层的交汇处围岩随着时间的长期变形量会更大,这对洞室的稳定性有着一定的影响;对于水电站地下洞室的长期稳定性分析,充分考虑岩体流变效应是非常重要和必要的。

The rheological behavior of adjacent rock is one of the important factors that influence the deformation and long-term stability of underground cavern.Under long-term load,the rheological behavior of rock mass occurred,and the rheological phenomenon of weak intercalation becomees more obvious.As an engineering example,a large-scale underground cavern of hydropower station is studied,in which there are reciprocal chiasmata with several weak intercalations.Based on the visicoelasto-plastic rheological model of rock,the rheological characters of the surrounding rock mass are simulated by using FLAC3D software.Through the analyzing of the calculated results,the long-term stability of underground cavern is estimated by studying displacement,displacement velocity,stress and plastic zone.The results show that the rheological effect of underground cavern is very remarkable.As for several weak intercalations are adjacent to the underground cavern,the deformation of intercross between cavern and weak intercalations is large,which has someing influence on the long-term stability of underground cavern.It is very important to consider rheological effect for long-term stability estimation of underground cavern.