In this paper the method and procedure of stability study of the abutment of Tianfumiao arch dam is introduced and the corresponding reinforcement measures are suggested. Based on detailed investigation of engineering geology and hydro-geology

various possible mechanisms of unstability are analysed and different sliding boundary conditions are combined

shear strength and deformation modulus and various geological structural planes forming the boundary conditions are determined with both in site and lab mechanical tests on rock

distributions of stress strain and fracture zone are obtained after 3-dimensional elastic finite element analysis so as to cheek the reasonability of unstability mechanism and boundary conditions

safety factor of stability under combined conditions of various loads and boundaries is computed by means of ultimate equilibrium method for rigid body

and finally

effective reinforcement measures are suggested with respect to the most unstable boundary condition and the main factors governing stability. Also

the criteria of selecting value of shear strength of rock mass and various weak planes

principle of using test data

the comprehensive shear strength problems on heterogeneoue structural plane and combined structural plane are discussed.