Analysis of underground rock cavern in the vicinity of a fault
Chua, Alicia Jing Wen
Date of Issue2017
School of Civil and Environmental Engineering
Underground development has become a more increasingly considered solution for the limited land space in Singapore. The purpose of this study is to investigate the factors that may affect the stability of the rock cavern where fault lines are located its vicinity. The finite element Plaxis 2D software is used for the stimulation of the rock cavern under certain conditions. The excavation of the rock cavern is performed sequentially using 3 stages. Thereafter, the stability of the rock model is determined using the factor of safety value obtained. In addition, the vertical displacements of the roof and the horizontal displacements of the cavern side wall are also examined. In this study, the various factors that are analyzed includes the change in the Geological Strength Index (GSI) which is an indication of the rock strength, the change in the fault frictional strength, the change in the locations where the fault is situated as well as the change in the fault angle. The key findings from this study include: 1. A higher GSI value of the rock mass results in a more stable rock cavern with a higher factor of safety and vice versa. The magnitude of displacement of nodes on the crown and side walls is smaller for a rock mass with higher GSI value and vice versa. 2. A fault location that is intersecting the cavern may not necessarily result in a less stable rock cavern. A fault situated at the cavern crown has smaller displacement of the top crown node compared to when a fault is at the left of the cavern. 3. An increase in frictional strength of the rock would result in a more stable rock cavern. 4. In general, the safety factor of the rock cavern is greater for the case of a steeper fault angle of 70 degrees compared to a gentler fault angle of 50 degrees. 5. The fault angle does not affect the trends of the graphs as the shape of the graphs obtained is relatively similar for the case of fault angle of 70 degrees compared to 50 degrees. The fault location is more critical for determining the cavern safety factor compared to the fault angles. 6. A fault intersecting through a larger area of the cavern may result in a higher factor of safety as compared to when the fault is at the right of the cavern.
Final Year Project (FYP)
Nanyang Technological University