Engineers Australia

Investigations of the Xiao Tou landslide stabilisation in the Three Gorges catchment area, Hubei Province, China

Christine Hug

Abstract

The Three Gorges project on the Yangtze River in China is the world’s largest hydro-electric power plant. Since the first impoundment of the 660 km long reservoir, more than 260 landslides have occurred along the reservoir banks.

The study summarised in this paper comprised geological and geotechnical mapping in the area of Xia Kou, located on the Xiang Xi River, approximately 40 km northwest of the Three Gorges Dam. The study aimed to determine whether the reservoir, with its significant water level changes, triggered the landslides or contributed to movement of existing landslides.

The study area is located at the Xiang Xi River, a tributary of the Yangtze River, flowing into the Yangtze River 28 km up-stream of the Three Gorges Dam. Most of the slides occur on the western banks of the Xiang Xi River, where sandstones and claystones strike parallel the flow direction of the river and dip into the slope. Landslides are triggered by a joint direction also striking north–south but dipping towards the river. The joint surfaces are filled with clay which decreases the shear strength of the rock mass.

Stability analyses of the Qiao Tou Landslide in the north of Xia Kou were carried out. The analyses took into account seasonal variations in the reservoir water levels and showed that the discharge from 175 m to 145 m AMSL is critical. Therefore, the drainage of the slope along the surface of rupture is a considerable factor triggering sliding.

Existing remedial measures consist of a large number of surface drains which have already been destroyed by continuous movement within the slopes. Furthermore, protecting shotcrete surfaces showed some wet areas and are also partially cracked as is the infrastructure around the area.