STUDY OF GROUND REACTION CURVE (GRC) IN NON-CIRCULAR SHALLOW TWIN TUNNELS USING FINITE ELEMENT METHODS AND CONVERGENT MEASUREMENT RESULTS

• Main Author: Husain Taherdito, Ali
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/42061
• Institution: Institut Teknologi Bandung

Nanjung Water Tunnel is an example of a non-circular shallow twin tunnel that was built to become the solution for annual flooding in the Citarum River area. The tunnel structure is mostly built on sandstone lithology which has poor rock strength. At each tunnel advance excavation, deformation will occur in the tunnel wall that would cause the tunnel to collapse. A two-dimensional numerical model is needed to find out the stability of the tunnel. The first step is processing the rock data to get the characteristics of the rock mass which will later be input into Phase2 software. After that, the model is processed to obtain a support capacity diagram, yield element, and tunnel deformation data. The deformation data then is processed to make a ground reaction curve to later be analyzed. From the ground reaction curve, it can be concluded that when the support equipment is installed, the deformation is 1,09 mm. The pseudo internal pressure that occurs when the tunnel deformation is 1,09 mm is 0,06 MPa. The rock is still in an elastic zone until the curve reaches its non-linear point. The value of deformation that occurs in non-linear point is 1,17 mm and the pseudo internal pressure is 0,048 MPa. The support system is installed when the rock still in an elastic zone, so it can be concluded that the installation of the support system is in the right position. By considering the yield element, strength factor, and the support capacity diagram formed on the model, it can be concluded that the tunnel is stable because the safety factor of the support equipment is still greater than five.