Analysis of underground excavations in rocks

• Main Author: Guo, Er Hang
• Other Authors: Low Bak Kong
• Format: Final Year Project
• Language: English
• Published: 2015
• Subjects: DRNTU::Engineering::Civil engineering
• Online Access: http://hdl.handle.net/10356/64121
• Institution: Nanyang Technological University

The excavation act changes the force field of the rock’s physical environment. The potential instability and displacement surrounding the excavation opening is an incessant threat to the safety of the men and the facilities inside. Therefore, it is essential to understand the causes of instability of rock mass, predict the possible behaviour of rock movement and take it into the design consideration. This project is to perform analytical and numerical analysis of underground tunnels and caverns in rock excavation. Studies are carried out to estimate the stability and the displacement of the rock excavations by using the closed form solution for circular tunnels. The induced stress is computed based on Kirsch Equation. The displacement and radius of the plastic zone can be derived by Duncan Fama Equation. The results from the close form solutions will be compared with the results from Phase2 program. The comparison between horseshoe shaped and circular tunnel and the effects of excavation in stages will also be discussed. Due to the uncertainties of rock mass properties, reliability analysis was conducted to estimate the probability of failure for the rock mass surrounding the excavation. The probability analysis was performed to account for the limit state of displacement and plastic zone radius under hydrostatic stress field. The reliability index was calculated based on Low & Tang’s algorithm in 2004. The result would then be compared with the result by @Risk program based on Monte Carlo Simulations (MCS). Furthermore, another analysis using Response Surface Method (RSM) was performed to compare with the previous result.