西南某水电站谷底深厚覆盖层与卸荷松弛带特征及其成因机制分析

CHARACTERISTICS AND GENETIC MECHANISM OF A DEEP OVERLAY AND ITS ASSOCIATED UNLOADING AND RELAXATION ZONE IN THE BASE OF RIVER VALLEY OF A HYDROELECTRIC STATION IN SOUTHWESTERN CHINA

钻孔揭示,该水电站河谷谷底发育着深厚覆盖层及卸荷松弛带。深厚覆盖层纵向上可以分为3层:下部和上部为正常的河流相,中部为多成因堆积物加积层;谷底浅表部岩体结构松弛,完整性差,裂隙张开、泥质充填,裂面严重风化锈染。研究表明,谷底松弛是由于河流切至谷底时造成应力集中,导致岩体剪切破坏;并经过漫长的卸荷回弹及风化作用在谷底形成一定厚度的松弛带。

Boring hole data showed that there was a deep overlay and an associated unloading and relaxation zone in the valley bottom of a hydroelectric station in southwestern China. The deep overlay could be vertically divided into three layers. The upper and lower parts were normal river faces, while the middle part was a sequence of aggradation of multi - genesis deposits. The rock mass in the valley bottom was relaxed on structure, bad integrality, splay cranny and fill with clay, weathering badly in the faces of cranny. Study on the relaxation zone in the base of river valley showed that when far -flung unloading rebound tion zone. the fiver cut adown, it caused stress concentration and led to shearing failure. After and weathering, the rock mass in the valley bottom formed certain thickness of relaxation zone.