综合物探技术在大古水电站建基面优化选择中的应用

Application of Comprehensive Geophysical Prospecting Technology in the Selection of Foundation Surface for Dagu Hydropower Station

大古水电站坝址区地处雅鲁藏布江上游段高山峡谷地貌的“V”型河谷中,河谷覆盖层主要为强透水性冲积漂卵石,基岩为喜山期侵入黑云母花岗闪长岩,招标图阶段原定建基面最低高程为3333m,在围堰防渗墙施工及开挖过程中发现地质条件好于预期,建基面高程存在优化的可能性。采用声波、钻孔录像、钻孔变模等物探技术在覆盖层未开挖完成前对坝基岩体物性参数进行测试,并结合相关设计规范要求对坝基岩体质量进行分类评价,从而使大坝建基面优化5m,最低高程抬升至3338m。综合物探手段的提前介入,能尽可能地优化提升建基面高程,节约了工程总投资和时间。

The dam site area of Dagu Hydropower Station is located in the“V”type valley of the Alpine Canyon landform in the upper reaches of the Yarlung Zangbo River.The overburden layer of the valley is mainly strong pervious alluvial drifting pebble,and the bedrock is biotite granodiorite intruded in Himalayan period.In the bidding drawing stage,the minimum elevation of the original foundation surface is 3333m.During the construction and excavation of the cofferdam cutoff wall,it is found that the geological conditions are better than expected,and the foundation surface elevation is possible to be optimized.In this paper,acoustic wave,borehole video,borehole deformation and other geophysical techniques are used to test the physical parameters of dam foundation rock mass before the completion of overburden excavation,and the rock mass quality of dam foundation is classified and evaluated in combination with relevant design specifications,so as to optimize the dam foundation surface by 5m and raise the minimum height to 3338m.This paper shows that the advanced intervention of integrated geophysical exploration methods can optimize and upgrade the elevation of the foundation as much as possible,saving the total investment and time of the project.