Experiences learned from engineering geological investigation of headrace tunnel on sedimentary rock—xekaman3 hydropower project—Lao PDR

Abstract

Xekaman3 hydropower project is located in Sekong province, Southern of Lao PDR. Site investigation for the project was carried out from January 2003 to May 2010 at damsite, water intake, headrace tunnel (7,400 m) and powerhouse area. Unfortunately, for the tunnel section from vertical well No 1 (GD1) to vertical well No 2 (GD2) with the length of 710 m, many complex geological phenomena happened and it influences significantly the whole construction scheduled and total investment of the project. This paper presents the causes of those phenomena, ways to solve problems and methods of improvement for the tunnel section mentioned above. The authors also mentioned some experiences learned through geological investigation process for headrace tunnel of Xekaman3 hydropower project and possibility of applying these experiences for the projects with similar geological conditions.