Effect of two circular tunnels on ground responses during earthquake

• Main Author: Sutejo, Wynne Mirabel
• Other Authors: Budi Wibawa
• Format: Final Year Project
• Language: English
• Published: 2019
• Subjects: DRNTU::Engineering::Civil engineering::Geotechnical
• Online Access: http://hdl.handle.net/10356/77436
• Institution: Nanyang Technological University

The presence of underground structures like tunnels, have been known to have an amplification effect on the ground surface, especially on the dynamic responses. This project presents a parametric study of the size and location of twin circular tunnels to investigate such effect on the ground responses under seismic loading. The ground responses were analysed based on horizontal peak ground acceleration (PGA), horizontal peak ground velocity (PGV), and horizontal peak ground displacement (PGD), simulated using a finite element program: PLAXIS 2D. Twin circular tunnels were embedded in an 80 m-thick loose sand lying on top of granite as the bedrock. The soil models were 720-m in width with the tunnels located at the centre axis of symmetry. Absorbent boundaries were used in the dynamic analysis, and a real acceleration time-history data from 2014 Ferndale, California earthquake was adopted to imitate an earthquake in Singapore settings. The tunnel parameters studied including the embedment depth, tunnel diameter, and separation distances between tunnels. The results obtained showed that the existence of tunnels had induced an amplification on seismic ground responses although its peak may not be directly above the tunnels yet in some distance away from the tunnels. The amplification effect became stronger as the tunnels buried deeper. Moreover, tunnels with larger diameter also experienced greater amplification until the diameter reached 8 m. Nonetheless, little correlation can be observed by comparing the results of different separation distances.