叶巴滩水电站高地应力现象及地应力场反演分析

Inversion Analysis of High Geostress Phenomenon and Geostress Field of Yebatan Hydropower Station

为了研究叶巴滩水电站坝址区的地应力场特征,通过现场地质调查,对坝址区高地应力现象的发育形态特征和空间分布特征进行描述和分析,结果表明:坝址区岩芯饼化发育的强烈段多分布在河床以及两岸低高程;片帮现象以轻微片帮和中等片帮发育为主;岩芯饼化和片帮集中发育段可判定为应力集中带。同时,根据坝址区工程地质条件和实测地应力资料,通过数值反演分析方法,考虑地形地貌和断层对初始应力场影响,对坝址区的初始应力场进行反演分析。结果表明:反演应力值与实测应力值基本吻合,能够较合理、准确反映坝址区的初始应力场;坝址区的初始应力场是由自重应力场和构造应力场叠加而成,且以水平向构造应力为主;坝址区应力场可以大致划分为应力松弛带、谷底的应力集中带、岸坡应力过渡带和岸坡深部的应力平稳带;在模型边界断层上下盘附近会有一定的应力集中现象,形成高地应力区。

In order to study the characteristics of the geostress field in the dam area of Yebatan Hydropower Station,a field geological survey was conducted to describe and analyze the development forms and spatial distribution characteristics of the high geostress phenomena at the dam site.The results show that the strong sections of core cake development at the dam site are mainly located in the riverbed and at the low elevation of both banks;the flaking phenomenon is mainly characterized by slight flaking and medium flaking;Stress concentration zone can be defined as core discing and strip concentration.At the same time,according to the engineering geological conditions and in-situ stress data of the dam site,the numerical method is used to invert the initial stress field of the dam site,which is considering the influence of topography and fault on the initial stress field.The results show that the inversion stress values are basically consistent with the in-situ stress values,and this reflects that the initial stress field of the dam site is reasonable and accurate;the initial stress field of the dam site is composed of gravity stress field and tectonic stress field and the horizontal tectonic stress is the main stress.The stress field of the dam site can be divided into stress relaxation zone,stress concentration zone of the valley floor,stress transition zone of the bank slope,and stress leveling zone of the deep bank slope;there will be a certain stress concentration phenomenon near the footwall of the model boundary fault,forming a high in-situ stress area.