大岗山坝区花岗岩蚀变特征及工程地质特性研究

Alteration and geological characteristics of granite in dam area of Dagangshan Hydropower Station

大岗山高拱坝坝区花岗岩在多期次蚀变作用下形成多种蚀变岩类,通过现场地质调查和室内岩样分析以及宏观-微观对比,查明了蚀变类型、空间分布规律及矿物学特征,并结合现场试验对其工程地质特性进行了研究。研究表明:区域复杂的构造环境造就了坝区花岗岩的不同种类和程度的蚀变,蚀变类型有热液交代、动力构造和次生风化蚀变;蚀变岩受构造影响较大,主要发育分布在断层和节理密集带附近,X衍射数据表明蚀变生成了一定量的黏土矿物绿泥石;蚀变花岗岩纵波波速和变形模量都有一定程度的降低,弱化了岩体质量。研究成果为深入分析大岗山坝区地质力学特性及工程建设提供了可靠基础依据。

Under multi - stages alteration, the granite in the dam area of Dagangshan Hydropower Station has formed a variety of altered rocks. Through geological investigation and lab rock analysis, and in combination with macroscopic and microscopic a- nalysis, the alteration types, spatial distribution as well as mineralogical characteristics were studied, and also the geological en- gineering characteristics was evaluated by field test. The complicated regional tectonic environment has created the different types and degrees of alteration that includes types of hydrothermal metasomatism, tectonic force and weathering. Mainly affected by tec- tonic influences, the altered rocks concentrate in fault and joint fissure band, and a certain amount of chlorite yielded by altera- tion was found by X - ray diffraction test. Longitudinal wave velocity and deformation modulus of altered granite reduced to a cer- tain degree, which illustrated that alteration effect weakens the rock mass quality.