Abstract: The dam site of Tingzikou Power Station is located in red bed sedimentary rocks area,and there are many structural planes in this area. Through in-situ direct shear tests on 21 sets of typical structural planes,the shear strength properties of the structural planes were revealed. Furthermore,statistics of the shear strength parameters were obtained by means of arithmetic mean value and diagram. The statistical results by the two methods are similar in general. The research findings not only serve as the basis for the design of this project,but also could be taken as reference for other similar projects.

Key words: Tingzikou power station, structural plane, shear strength, direct shear tests