Analysis of force and strain distribution in soil and concrete tunnel due to a planar rock movement
Typ
Examensarbete för masterexamen
Program
Infrastructure and environmental engineering (MPIEE), MSc
Publicerad
2022
Författare
GHAFFARIAN MAHDOODI, Mostafa
MATHEW, Sion
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Rock movement in the vicinity of existing structures and infrastructure projects is of great importance as it can lead to major damages and loss if care is not taken. The response in the tunnel due to such movement has to be monitored and actions taken to prevent major loss. The aim of the study is to examine how a thin soil column and a concrete tunnel will be affected by a planar rock movement and thereby determine the location for placing a deflection measurement system in the right wall of the tunnel. The goal of the report is to act as an example for future studies regarding rock movement and its impacts on thin soil sections as conventional theories cannot be applied in such cases. To exemplify this, the case of an existing rock slope in Kvarnberget, Gothenburg where a cut-and-cover tunnel is planned to be constructed has been taken into account. The analysis was conducted both analytically and numerically.
A planar fault in the rock was assumed along which failure would happen in order to simplify the analysis conducted analytically and as the numerical analysis was performed in 2 dimensions. In the analytical method, the forces acting on the rock block was determined, and the weight of the rock block was calculated. A theory was adopted to determine the failure in the thin soil column. Subsequently, the forces acting on it determined and the conditions of equilibrium of forces applied in the failure section. Following this, the lateral forces acting on the tunnel were determined, and a structural analysis performed to calculate the deflection taking place in the tunnel due to the rock movement. The numerical analysis performed using the software PLAXIS where some material properties were obtained from laboratory results while others were assumed. Several scenarios were created to understand how the results would vary accordingly.
From the numerical analysis, it was found that the failure wedge assumed in the soil column while performing the analytical analysis was similar. On comparing both analyses it was found that the results from the analytical results showed higher deflection. The point of maximum differential stress at the right wall was calculated to be at the intersection between the top and right wall and it was concluded that the deflection measurement had to be placed there.
Beskrivning
Ämne/nyckelord
Rock movement , numerical analysis , cut-and-cover tunnel , soil wedge , deflection measurement system