A case study of alteration effects in granitic rocks on rock cavern stability at Jinzhou of NE China

摘要

It was found that there exist various types of alternative rocks within the Jinzhou granite after a site investigation for sitting one rock cavern at NE China. These alternative rocks are resulted from intermediate-basic intrusive dykes in granitic rocks.The dykes are easily transformed to hydrothermal alterative rocks in the formof one sill or asweathered trough near ground surface. Some drilled cores at depth 50 to 100 m, are decomposed to fractures after exposure in the air and disintegrated into fine particles after setting in the water. They are regarded as weak rocks of grade IV, constituting potential threaten to engineering safety of rock caverns.Analysis on massive rock and clay size particles byXRDfound that the basic intrusive rockswere alterated to montonite under function of hot fluid. Large content of montonite made this rock are distinctive in swelling, disintegration, and other weaken features. These distinctive montonite in alternative rocks is one fundamental factor affecting cavern safety.