Stress Induced Problems in Himalayan Tunnels with Special Reference to Squeezing

摘要: There is a huge potential of underground constructions in the Himalayan region for hydropower, transport systems and conservation environment. However, tectonic activities have resulted with fragile regional geology. Moreover, high mountainous topography causes overburden pressure structures causing squeezing other stability problems. Thus tunnelling can only be materialised by applying professional scientific approaches.This thesis focuses on stress induced problems special reference to squeezing. Main objectives this study were review check validity available tunnel assessment methods, carry out relevant laboratory tests interpret results, use numerical modelling code. In present study, two projects been used as case studies, both located Nepal region. These are Khimti1 hydropower project - completed project; Melamchi water supply yet constructed. Both include tunnels through series weak rock mass strata stress.One factors that may cause level acting around opening. A fails when exceeds strength mass. If does not exceed strength, but sufficient up critical creep, it lead failure after some time. assessment, determination important. Creep carried gneiss has determined.The creep test curves calibrated obtain rheological parameters. Tunnel deformations including time-effect, calculated given level. Based results at various uniaxial levels, an equation obtained relation between strain rate Back analyses using empirical, semi-analytical analytical methods FLAC3D code; found close agreement convergence measurements Khimti tunnel. So these design.In 66 cases from world was observed (corresponding type) significant influence phenomena. prediction criteria based classification alone, need updated well. Similarly, ‘valley side effect topography’ deformation project. It opened area further correlate valley increase