ROCK RELAXATION CHARACTERISTICS OF LAYERED FOUNDATION ROCK MASS FOR HYDROPOWER STATION IN SOUTHWEST REGION

Relaxation and its relaxation zone of excavated foundation rock mass is a kind of common phenomenon in hydropower project. They have important influence on the foundation rock mass quality. The foundation rock mass after excavation is bound to produce new blasting cracks along with the excavation unloading and stress release. Although it has not been further weathered, rock mass can form a relaxation zone in the superficial depth, with its relaxation and unloading. Therefore, determination of relaxation zone thickness is of great significance in engineering. The paper is based on the field of geological environment condition survey and acoustic test and the indoor synthetic analysis. It studies a relaxation zone thickness and characteristics of layered foundation rock mass and analyze the foundation rock causes of deep relaxation. On the basis, it analyses the relaxation zone that has influence on the engineering properties of the foundation rock, which has instructive function for dam foundation excavation practice of similar projects.