倾斜坡体中水工高压隧洞围岩应力场特性分析

把岩体看作均质、各向同性连续透水弹性介质，引用Harr(1962)提出的镜像理论，结合Zienkiewicz(1958)和Femandez(1994)所作的假定，推导了倾斜地表下水工压力隧洞内水外渗产生的有效应力：假定初始应力场为自重应力场，结合现有的部分成果，详细分析倾斜地表下水工压力隧洞初次充水和正常运行期围岩中的应力场分布。倾斜地表下水工压力隧洞在满足挪威准则的前提下，围岩最小主应力在一定范围内为拉应力，拉应力区呈蝶形分布，且其范围随地表倾斜角的增加而扩大：倾斜地表下压力隧洞最易出现水力劈裂现象的不利位置是围岩拉应力蝶形区伸展最大的方位：隧洞埋深增加1／8最小覆盖层厚度可有效地减小围岩中拉应力区的范围：陡倾地表下压力隧洞设计应慎用水工隧洞设计规范的边坡高限角。

STRESS ANALYSIS OF SURROUNDING ROCKS OF HYDRAULIC HIGH PRESSURE TUNNELS UNDER STEEP ROCK SLOPE

The distribution of effective stress induced by the seepage from pressure tunnel into rocks under a rock slope is estimated by using the image well method proposed by Harr(1962) and the assumptions made by Zienkiewicz(1958) and Fernandez(1994). The rocks are treated as a homogeneous,isotropic,porous,elastic medium. When loaded by its own weight only,the stress distribution in the rocks surrounding pressure tunnel after excavation and water filling is studied. When the pressure tunnel is designed with the Norway rule,the minor principal stress is tensile in the vicinity of tunnel. The tensile area is like a butterfly and it will be extended with the increment of the rock slope angle. The potential hydrosplitting of rocks around pressure tunnel is taken into account and it will appear in the extended orientation of butterfly. If the thickness of tunnel overburden is increased with 1/8 of the minimum one,the tensile area will be decreased effectively. For the pressure tunnel under steep rock slope,the highest slope angle should be chosen very carefully.