黄河拉西瓦水电站坝区花岗岩风化研究

风化作用对于岩体工程地质性能的降低不言而喻。研究探讨重大水电工程岩石风化作用机理对于工程区岩体风化带划分、风化渐进性分析、表征岩体风化特征指标的选择及力学性质参数取值等具有重要意义。文章从风化作用本质、化学元素迁移、风化作用类型等角度,对拉西瓦水电站坝区花岗岩风化作用机理进行了探讨。结合本区气候演化、岩石性质、地形条件等综合分析认为:在浅表河谷范围内,风化形式以岩石胀缩作用和冰劈作用为主,而化学风化作用并不强烈。论文采用量化指标对岩体进行风化带划分,选取的定量指标有平硐纵波速度Vp、钻孔RQD、裂隙间距与单元面积节理数等。在此基础上,利用电站20余a来丰富详实的地质、物探、岩体测试等大量资料,采用定性分析与定量划分相结合的研究方法,对黄河拉西瓦坝基花岗岩体进行风化分带,得出坝基岩体风化带总体空间布局。

Study on granite weathering at damsite of Laxiwa Hydropower station on the Yellow River

It is well known that weathering can reduce the quality of rockmass.Therefore,it is the common practice to study the mechanism of weathering of rocks by classification of wheathering zones,using certain index composing mechanical parameters of rockmass.This paper analyses mechanism of weathering of on granite at damsite of Laxiwa Hydropower station on the basis of nature of weathering,migration of chemical elements and types of weathering.It is concluded according to climatic development characteristics,rock properties and topographic features,that the main process of weathering are expansion,contraction and frost.But chemical weathering is not strong at superficial slope of dam site.The paper uses quantitative index,such as longitudinal wave velocity on exploration adit,borehole RQD,spacing and joint numbers in unit area,to classify different weathered degree.Consequently,spatial distribution of weathering zone of granite at dam base aws analysed.