MESH DEPENDENCY IN NUMERIC MODELING FOR DETERMINATION OF THE FAILURE ZONE THICKNESS AROUND THE TUNNEL BASED ON MOHR COULOMB CRITERIA

• Main Author: Putri Pratiwi, Anindita
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/57583
• Institution: Institut Teknologi Bandung

Failure zone is an important thing that can be used to determine how to assess and treat tunnels. The thickness of the failure zone can be modeled using the finite element method in RS2 software. The tunnel modeling results are based on the mesh using. The tunnel modeling was applied on fair and very poor rock mass with a depth of 500 m with k factor values 1 and 2 at a 4 m diameter tunnel. The analysis that was applied in this modeling by varying the number of nodes around the excavation with triangular elements with 3 points. The number of nodes on the excavation are intervals between 25 until 400 with multiples of 25. By varying the number of nodes around the excavation, the total number of elements and nodes in the whole modeling will increase along with the increasing number of nodes on excavation. The value of the failure zone depends on total elements and nodes in tunnel modeling. The relationship between the average failure zone and the mesh is fluctuating and not always increase with the increase of elements and nodes, but there is a tendency for the failure zone to increase with the increase in the number of elements and nodes. The weaker the rock, the greater the value of the failure zone that will be generated. In both fair and very poor rock mass, for the value of k = 2, the more elements, the smaller the value of the failure zone on both walls (right wall and left wall). The relationship between the failure zone and the number of elements is the best in very poor rock mass modeling with a value of k = 1 which produces 0.528 correlation coefficient.