Performance of the Inducing Joints in <i>Xiaowan</i> Arch Dam with Reservoir Impounded to Normal Water Level

To reduce the tensile stress at dam heel, inducing joints have been set in Xiaowan arch dam; they were designed to work without water pressure. After the reservoir was impounded to the normal water level of E.L.1240m, monitoring data showed that almost half of the inducing joints were working with water pressure, but leakage remained small. It also indicated the opening and shear deformation of all the inducing joints were small, and the joint surface remained in compression although the compressive stress was decreased by 2.03MPa~9.29MPa. So it can be concluded that the inducing joints are generally working at closing and compressive state. However, some abnormalities were detected: large seepage pressure and increasing crack width in block No.16 which is at the right end of the inducing joints; 5 small cracks appeared with leakage water at the downstream inner surface of the inspection gallery of the inducing joint in block No.22. Therefore, close attention has to be paid to the crack propagation around the inducing joints for the safety monitoring in future.