Structural controls on groundwater inflow analysis of hardrock TBM

Abstract Results of analyses on localized jointing system are presented to study the link of groundwater inflow and joint orientations along the 2000 m excavation of Tunnel Boring Machine (TBM-1) site, Karak in conjunction with the construction of Pahang–Selangor Raw Water Transfer Tunnel project. Geology along the tunnel route is predominantly the Main Range Granite Batholith with a lesser extent of metasedimentary rocks of the Karak Formation. Structurally, TBM-1 is dominated by joints oriented at N–S, NW–SE, and NE–SW directions. Strike slip faults that cross-cut the intrusive Main Range Granite rocks trending faults formed the most prominent structures in the vicinity of the Karak. This section of tunnel alignment consists of 2000 meters in length of Ch.8,821.77 m to Ch.10,821.77 m; 456 joints were mapped to create anisotropic conditions of rock section. Eleven significant locations experienced stoppages, thereby affecting the TBM daily progress, and such stoppages were mainly caused by sudden high-pressure groundwater inrushes or wet joint condition. Potential leakage places are identified by three main types of joints orientations. The most permeable tunnel section is in parallel with the main lineament orientation, followed by perpendicular to the tunnel drive direction, and crossing some voids that create pocket water zones.