METODE HORIZONTAL-TO-VERTICAL SPECTRAL RATIO DAN FINITE ELEMENT ANALYSIS UNTUK STUDI SITE EFFECTS DAN KERENTANAN BANGUNAN: KASUS TEROWONGAN “XX”, CIMAHI

• Main Author: Aufara Leader, Samhanni
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/66901
• Institution: Institut Teknologi Bandung

Tunnels are passages that cut below the surface and generally have openings at their two ends only. The threat of tunnel instability does not stop after the construction process is complete, but continues to come through disturbances such as ground motion. "XX" Tunnel is a tunnel in Cimahi, West Java, located about 9 kilometers from the Lembang Fault and will function as an inter-province transportation course. Field observations showed a fault between basalt and tuff rocks where the “XX” Tunnel is excavated in the shape of a horseshoe with an arc radius of 4 meters. These particular cases need to be considered as a potential threat to the tunnel’s stability, therefore, an investigation was conducted using microtremor data for site effects studies using the HVSR method and a MohrCoulomb failure criterion in the “XX” Tunnel area. Microtremor data processing resulted in dominant frequency, amplification, Seismic Vulnerability Index, and sediment thickness values. These values are mapped after going through interpolation to predict data at unsampled points. A prominent trend found above the tunnel path is the presence of anomalies in the dominant frequency, Seismic Vulnerability Index, and sediment thickness that cuts through the "XX" Tunnel at the junction between basalt and tuff units with a NE-SW orientation. Further analysis of the H/V rotation indicates the existence of a geological structure continuity that has not yet been identified in the anomalous area. Finite Element Analysis modeling was carried out to test the vulnerability of the tunnel to overburden stress and faults whose interpretation was then reviewed with a Mohr diagram. The results of the Mohr diagram analysis show that the "XX" Tunnel begins to have a vulnerable point in overburden conditions 50 meters below the surface, while the presence of a fault above the tunnel face does not affect the stability of the tunnel.