Monitoring and characterizing the deformation of an earth dam in Guangxi Province, China

Abstract

Failures and severe deformation of earth dams have been reported frequently in the past decades. Extensive studies have been performed to monitor dam displacements to develop dam remediation plans. However, the long-term monitoring of dam displacements and the effects of remediation on dam deformation are rarely studied. In this study, the vertical and lateral displacements of an earth dam in Guangxi Province, southwestern China, were monitored over an 18-year period. The piezometric pressure was measured for the analysis of triggered seepage. Furthermore, acoustic testing and borehole television tests were performed to examine the integrity of the cutoff wall that was built to prevent dam leakage and excessive deformation. The results show that the largest lateral displacement of 65.8 mm and the maximum settlement of 178 mm are both located at the center of the dam and that the lateral displacement and settlement decrease gradually from the center to both abutments. Moreover, greater settlements were observed on the side of the dam upstream of the cutoff wall. The lateral displacements are dominated by the hydraulic pressure of the impounded water. The dam settlements are generally determined by the thickness of the compacted soil along the longitudinal section. The analysis shows that the greater settlements on the upstream side of the dam are attributed to dynamic seepage induced by the water level changes in the reservoir, indicating that the cutoff wall effectively alleviated the seepage effects on the downstream side of the dam. Thus, the dam's upstream face should be remediated to minimize the dynamic water-level effects.