Abstract：Stability analysis is made on the system composed of fault band and surrounding elastic rockmasses considering water weakening and strain gradient. The deformation of ductile fault after rock burst is investigated. It is found from experimental measurement that the shear strength and the absolute value of the slope of stress and strain curve are decreased with water content. Considering the deterioration of strength，the distribution rules of plastic shear strain and total plastic shear strain in shear band are proposed based on gradient-dependent plasticity. Besides，the relation between shear force and relative plastic shear displacement is also presented. The analytical result shows that the plastic shear strain and the plastic shear displacement decrease with water content. Larger water content leads to shorter elastic stage，lower dissipated potential energy and lower external force work. In addition，the released elastic strain energy increases as water content decreases. According to the analytical solution of axial stress-axial strain curve of rock specimen in uniaxial compression proposed by authors and experimental results，water content affects the softening modulus. The post-peak slope of shear stress and shear displacement curve of the system is presented considering the influence of water content on the softening modulus. It is shown that increment of water content reduces the possibility of instability.
