Abstract: The left dam abutment of Yangzhuang Reservoir Project contains large quantities of sedentary soils deteriorated from quartz dolomicrite,muddy and silty dolomite. These soils, which are characteristic of high moisture, low dry density and high porosity, are low in strength and highly compressible. They are not suitable as the underlying bedding of dam foundation. Excavation of these soils would increase the quantity and cost of the work. A particular study is performed on the engineering properties of the totally weathered rocks at the left dam abutment, with appropriate treatment measures proposed.