About the Damage of the Penstock of Xekaman 3 Hydropower Plant Due to Sliding and the Remedial Measures for Power Generation

Abstract

The Xekaman 3 hydropower plant is located on the territory of Lao PDR and has a 6008m long headrace tunnel, a 1110m long penstock a, 520m gross head and installed capacity 250 MW. The headrace tunnel and the penstock area consist of sandstone, siltstone and microdiorite. The penstock lies on the site of an ancient stabilized landslide, but due to the construction of the cut slope upstream of the power house, the ancient landslide reactivated, creating a rupture of the penstock and an inclination of vertical shaft N2, so the electrical generation has been stoped. At present, the measures for stabilizing the landslide are being carried out such as removing the weight of soil from the head of landslide, dewatering the cut slope and constructing the concrete shearpile wall, but it is difficult to stop completely the displacement of landslide. In order to early generate electricity, the shorterm alternative of remedial measures are recommended with phylosophy “living together with the landslide. They are measure placing the compensator at horizontal penstock and measure placing the telescopic at vertical shaft N2 which permit the penstock operating safely while the landslide is moving with rate of 5mm/ month. Monitoring the landslide displacement is caried out strictly. At present the power house is generating with one operational unit.

1. Introduction

The Xekaman 3 project is located on the territory of Lao PDR having a 101.5m high concrete face rockfill dam. The energy line consists of the 6008m headrace tunnel with an internal diameter of 4m and a 43.3m high surge tank with an internal diameter of 12m. The tunnel from the surge tank to the power house is called the penstock with a concrete lining and a steel lining. After the surge tank is the 182m long horizontal penstock, then a 171.83m high vertical shaft , connected to another 710.9m long horizontal penstock with an internal diameter of 3.2m. After that there is an inclined 65.75m long open penstock connected to a vertical shaft 91.86m high with an internal diameter of 3,1m. Then the horizontal penstock in 205,5m with internal diameter of 3.1m connected to the power house with an installed capacity of 250 MW, gross head of 520m and having average annual power production of 982,000,000 KWh.