ANALYSIS ON THE EFFECTIVENESS OF INITIAL SUPPORT ON SWELLING CLAY – A CASE STUDY OF MANIKIN DAM DIVERSION TUNNEL IN KUPANG

• Main Author: Stephen
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/65824
• Institution: Institut Teknologi Bandung

The diversion tunnel is one of the main constructions before the construction of the Manikin Dam in Kupang Regency, East Nusa Tenggara Province. This diversion tunnel is built through the Bobonaro formation, which is dominated by clay. During the construction of the diversion tunnel, a problem occurred, which is the large convergence on the tunnel wall, resulting in damage to the initial support system that had been installed in the tunnel. The large convergence value that occurs is caused by the swelling phenomenon of the clay material penetrated by the diversion tunnel construction. This swelling phenomenon results in changes in the ground strength of the rock mass surrounding the tunnel and causes excessive swelling pressure on the tunnel wall which then results in damage to the initial support system. In this study, 2-dimensional numerical modeling was carried out to determine the actual conditions of each stage of tunnel excavation when the swelling phenomenon happens so that the trend of changes in ground strength values and the influence of swelling pressure is obtained. Then, there are two alternative methods that are carried out to overcome the deformation caused by the swelling phenomenon, namely by (1) larger steel rib H-beam WF300x300 with the addition of an invert beam and (2) original initial support with forepoling umbrella roof support and the addition of an invert beam. The results of the swelling handling method with larger steel rib H-beam WF300x300 with the addition of an invert beam reduced the convergence value to 14 cm, whereas the second alternative which is the original initial support with forepoling pipe roof umbrella, and the addition of an invert beam, results in a decrease of the convergence value to 8 cm. The results of this study are the alternative with original initial support combined with forepoling umbrella roof support and the addition of an invert beam is the best handling method to overcome the swelling phenomenon that occurs in the Manikin Dam diversion tunnel.