Use of geosynthetic clay liner as a remedial measure of claystone degradation in Lam Ta Khong hydropower plant

Abstract

In this study, the downstream slope of a dam impounding the upper reservoir of Lam Ta Khong (LTK) hydroelectric energy storage in Thailand was found to slide at a higher pace during the rainy season. After a thorough site investigation, laboratory tests, and numerical modeling to identify the main cause of the movement, it was found that as rainfall infiltrated the upper soil layer, the claystone of the downstream slope deteriorated when in contact with the water. As a remedial measure, 174,750 m2 of geosynthetic clay liner (GCL) was used to cover the entire downstream slope of the dam, and proved to be an effective and economical solution for reducing the ongoing movement. The GCL included a textured high-density polyethylene (HDPE) layer for improving the resistance and minimizing the slippage at the interface between the GCL and underlying rock. Before the dam's remediation, the settlement point demonstrated a movement of nearly 0.1 m/year. In contrast, after the placement of the GCL, almost all settlement points moved less than 0.1 m for a recorded period of more than 4 years.