Abstract:For there is dissension in the maximum principal stress orientation obtained by in-situ measurements by different means,geostresses in the three directions are presented by in-situ measurement and geomechanical analysis,to investigate the status of stability of rock mass of bilateral dam abutment and get reliable theoretical foundation for its design and construction. The in-situ measurement adopts stress relief by overcoring method,using bore strain gauge 36–2 to collect data. And the elastic modulus experiment is conducted indoors. In terms of these experimental data,the magnitude,azimuth,inclination of the geostress of rock mass of dam abutment can be figured out,through which the distribution character of the ground stress of rock mass of the hydraulic engineering can be determined. By geomechanical method,the in-situ geological information about conjugate joints,fault occurrence,rake angle,shift symbol of fault slip and so on are analyzed,through which the principal stress orientation can be elicited by stereographic projection. By the study of the above two aspects,some conclusions are drawn:(1) The in-situ metrical results accord with the geomechanical results well,which indicates better reliability. (2) The mode of stress action in the region of measurement point gives priority to terrain and tectonic stress control. The magnitude of the maximum principal stress is between 11.8 and 20.8 MPa,and the direction as a whole is NW-NNW in the left bank,and N-NNE in the right bank,parallel to the bilateral cliff faces approximately and inclining to the bottom of the cliff. (3) Three-dimensional stress state in the region belongs to the potential strike-shift pattern.