Abstract:The integrated application of hydro-fracturing and borehole deformation in the study of geostress field and slope rock mass mechanical characters in a dam site is presented. This study includes the quantity and distribution of horizontal principal stresses,static elastic modulus and deformation modulus in the measuring zones. The results indicate that the geostresses of right bank are obviously higher than those at the left bank and the moduli of shallow rock mass are almost lower. The results of both measurements reveal the shallow and riverbed rock mass mechanical characters. At last,the unloading mechanism of slope is analyzed based on the measurement results and the primary unloading boundary is also provided,which can provide reference to the logical excavation of the arch dam bank slope.