峡谷地区大型地下洞室群岩体初始地应力场反演分析

Feedback analysis of initial earth stress field of rock masses in large-scale underground openings situated in valley zone

合理地确定地下洞室群岩体初始地应力场对于地下洞室群的总体布局、支护设计有着重要的意义。本文提出了一种依据少量实测地应力资料反演地下洞室群岩体初始地应力场的方法。这种方法假设远古地形是一无起伏的夷平面,认为岩体初始地应力场主要由处于远古地应力状态下的远古地形经过漫长的地形剥蚀形成,而远古地应力场由地质构造运动和岩体自重形成。以有限元数值分析为基本手段,提出了可以考虑构造运动、岩体自重和地形剥蚀等多因素的岩体初始地应力场反演思路。通过某水电站地下厂房区域岩体初始地应力场反演的工程实例分析,验证了这一方法的可行性和实用性。

Initial earth stress in rock masses is the basic load of surrounding rock of large-scale underground openings of hydropower station, and it also is an important factor affecting the stability of the underground openings. Consequently, it is very vital for the openings layout and support structure design to rationally determine regional earth stress field of the openings surrounding region. This paper put forward the method about how to get regional earth stress field from only few earth stress data of measured points. This method introduced three hypotheses namely, taking ancient landform as a planation surface, assuming ancient earth stress field to be caused by gravity and tectogenesis, and supposing existing earth stress field to be induced by denudation of ancient landform with ancient earth stress field. Therefore, by virtue of finite element method, the idea, which can take rock gravity, tectogenesis and landform denudation into account, to get initial earth stress field of rock mass was presented. At last, the regional earth stress field of a water power station＇ s underground excavations was studied by back analysis using the above idea. The result shows that the method is feasible and practical.