白鹤滩坝址区不对称河谷地应力场演化规律分析

摘要

To discuss the evolution laws of in-situ stress field at Baihetan Dam site, the evolution process of in-situ stress is simulated using the Universal Distinct Element Code( UDEC) , by consideration of the valley asymmetric development. The nu-merical results are as follows:the phenomenon of high in-situ stress fold occurs in the river valley bottom with an obvious stress concentration at the depth of 130m, and the magnitude of the maximum principal stress is 28 to 34 MPa. The in-situ stress field along the bank slope is characterized as the belt distribution, which can be divided into the stress relaxation zone and original stress zone. The horizontal depth of stress relaxation zone is approximately 200m at the left bank and 120m at the right bank. In addition, further analysis of the mechanisms of asymmetric stress evolution is carried out;it is found that the asymmetrical valley evolution is the main cause for the different in-situ stress of two banks, in which, a reciprocating process existed, including the stages of valley incision, landslides accumulation and valley bottom migration.%为探讨白鹤滩坝址区河谷地应力场演化规律,利用二维离散元程序( UDEC),在考虑河谷的不对称发育情况下模拟了地应力场演化过程,初步分析了地应力场的基本规律。分析结果表明：谷底出现高应力包现象,深度约130 m左右,应力集中明显,最大主应力量值约为28~34 MPa；谷坡地应力带状分布明显,分为应力松弛区和原岩应力区,其中左岸应力松弛区水平深度约200 m,右岸则为120 m左右。此外,进一步分析了河谷地应力场不对称发育的演化机制,认为白鹤滩河谷演化发育是地应力场不对称分布的主要影响因素,不对称河谷的演化发育是河谷下切、滑坡体堆积和谷底迁移三个阶段循环往复的过程。