甘肃省代古寺水库坝址区发育蚀变花岗岩,其蚀变特征直接影响岩体的工程特性,并对工程区永久和临时水工(施工)建筑物的安全性造成影响。综合分析工程区区域地质资料,通过野外地质测绘、取样试验分析和地球物理勘察等手段,以宏观和微观相结合的方式全面探讨坝址区蚀变花岗岩的工程特性。研究表明:蚀变花岗岩成因主要为岩浆及脉体热液交代,蚀变类型以黏土化为主;蚀变花岗岩集中分布于代古寺水电站下游70~180 m范围内河床及近河右岩低高程部位,蚀变深度集中在地表以下20~100 m范围;蚀变花岗岩岩石强度明显降低,孔隙率和吸水率显著增大,岩体完整性较好。研究结果对优化水工设计方案有重要的理论意义和工程应用价值。

Altered granite develops in the dam site of Daigusi Reservoir in Gansu Province. The alteration characteristics of altered granite directly affect the engineering characteristics of rock mass and the safety of permanent and temporary hydraulic (construction) buildings. The engineering characteristics of altered granite in the dam site area of Daigusi Reservoir were examined in macro-and-microscopic scales via field survey, sampling test, and geophysical prospecting. Results suggest that the altered granite is mainly caused by magmatic and vein hydrothermal metasomatism, and the alteration type is mostly argillization. Altered granite concentrates in the riverbed and the low elevation parts of the near-river right-side rock in 70-180 meters downstream of Daigusi Hydropower Station; the depth of alteration is concentrated in the range of 20-100 meters below ground surface. The altered granite is featured with remarkably reduced strength, increased porosity and water absorption, as well as sound integrity.