【正文】
may push sediment down the slope,or particles may slowly move or freezing and thawing. The term colluvium is used to describe sediments that are eroded,transported, and deposited on and at the base of slopes by deposits range from accumulations of coarse rock fragments to claysize particles but are monly a poorly sorted mixture of both coarse and finegrained particles. In a slop in which the rock is jointed but where there are no significant discontinuities dipping out of the slope which could cause sliding. In an extreme case,where the rock mass consists of near vertical joints separating columns of massive rock,toppling movement and failure may occur. For example aWahleach project is located 120 km east of Vancouver and power is generated from 620m of head between Wahleach Lake and a surface powerhouseb located to the Fraser flows through a 3500m long three meter diameter concrete encased steel lined shaft inclined at 48 to the horizontal, a 300m long lower tunnel and a 485m long surface penstock to the powerhouse. The tunnels were excavated mainly in granodiorite which varies from highly fractured and moderately weathered in the upper portions of the slope to moderately fractured and fresh in both the lower portions of the slope and below the highly fractured mass. Two main joint sets occur in the rock mass,one set striking parallel to the slope and other perpendicular to dip very steeply .Average joint spacings range from to few joints occur subparallel to the ground surface and these joints are most welldeveloped in the ground surface adjacent to the inclined investigations failed to reveal any significant shear zones or faults oriented in a direction conducive to sliding. The top