STABILITY OF THE TUNNEL IN THE FRACTURE ZONE USING 3D NUMERICAL MODELING

• Main Author: Faishol Arriq, Muhammad
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/84219
• Institution: Institut Teknologi Bandung

This final project presents a case study on tunneling through a 42 meters fracture zone with a cover depth only 11 – 32 m. The tunnel, which will serve as a two – lane one way road, has a horseshoe shape with dimensions of 12.8 meters in width and 10.5 meters in height. This tunnel is in Samarinda, East Kalimantan, Indonesia. The tunnel excavation was carried out using the top heading and bench method, with the top heading having a height of 6.2 meter and the bench 4.1 meter. This project focuses on the initial tunnel support system during the construction period which consist of shotcrete C16 10 cm, shotcrete C20 20 cm, micropile (Ø114mm), longsteel pipe roof (Ø114mm), rockbolt (Ø25mm), H – Beam W150 x 29.8, and wiremesh M7. A 3D numerical modeling was conducted to provide recommendations for the tunnel excavation lag length that results in the most stable conditions. The variations in the tunnel excavation lag lengths are 12 m, 24 m, and 42 m. The interpretation of sigma 1 indicates the formation of an arch effect around the tunnel, with tunnel displacement values in under 10 cm (JSCE, 2018). The support capacity diagram confirms that the induced internal forces acting on the support are still within the capacity of the initial lining, and the strain values remain below the critical strain line (Hoek & Marinos, 2000)