拉西瓦工程河谷区高地应力场反演与形成机理

Back analysis and multiple-factor influencing mechanism of high geostress field for river valley region of Laxiwa Hydropower Engineering

拉西瓦水电工程坝址区为高山峡谷地貌,受地质构造应力、自重、地表剥蚀和河流侵蚀卸荷等多因素影响而赋存有高地应力,河谷区钻孔岩芯饼化与探洞片状剥落现象明显。由于该区地应力场及其空间分布特征与多期地质构造运动及河谷演化历史等因素密切相关,要合理确定其三维地应力分布状况与大小具有较大难度和复杂性。采用多元回归与逐步回归相结合的方法对工程区域初始地应力场进行了详细反演,在此基础上,深入研究了河谷区地应力场的空间分布特征与规律,并就其形成机理开展了多因素影响效应分析,为我国西部强烈地质作用区高地应力研究及水电工程建设提供了具有参考价值的成果和工程案例。

The Laxiwa Hydropower Engineering is located at high mountains and valley regions, existing high geostress in the rock masses due to the multiple-factor influences such as tectonic stress, gravity, river and weathering erosion, etc. In the river valley region, discal phenomena of drilling cores and laminated exfoliation of surrounding rock in the exploration tunnels are obvious. The determination of the 3-D geostress field in the valley region is difficult and complicated, which are tightly related to the tectonic movements in different geological period and the evolution history of river valley. In this study, detailed back analysis of the 3-D ground stress field for the engineering region is finished. Based on the results derived from the back analysis, the spatial distributing characteristics and magnitudes of the 3-D geostress field are studied. Furthermore, focused on the formation mechanisms of the geostress field, the multiple-factor influencing effects are analyzed. The paper provides a valuable reference and engineering case for the study of high geostress field and the establishments of hydropower projects located at Western China, especially for those with strong geological actions.