STABILITY ANALYSIS OF TUNNEL B ON THE YOGYAKARTA-BAWEN TOLL ROAD SECTION AT STA 20+435 UTILIZING THE CENTRAL DIAPHRAGM METHOD USING 3D NUMERICAL MODELING.

• Main Author: Maulana Rifqi, Muhammad
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/76820
• Institution: Institut Teknologi Bandung

The Yogyakarta-Bawen Toll Road Project includes the Twin Tunnels, which are situated in Section 5 of the Temanggung-Ambarawa road (STA 20+273 to STA 20+679). These tunnels will be built via Bukit Banaran in the Kragan, Losari Village, Magelang Regency, Central Java. There are two twin tunnels that are 385 meters long (Tunnel A) and 405 meters long (Tunnel B), respectively. Each tunnel will feature three lanes of unidirectional traffic. One-way traffic will be allowed via each tunnel. The end destination of Tunnel A is Yogyakarta, while the final destination of Tunnel B is Bawen. The tunnels, which will be in the shape of a horseshoe with measurements of 20.18 m x 13.7 m and a total excavation crosssectional area of 223.6 m2, will be excavated using the central diaphragm method, cutting through various layers of soft materials. In this study, the stability of the Yogyakarta-Bawen Twin Tunnel Toll Road at STA 20+435 will be analyzed using the central diaphragm method with lattice girder support using 3D (three-dimensional) numerical modeling. The results from the 3D numerical modeling show that the excavation method using central diaphragm with lattice girder support can be utilized during the construction phase, as indicated by the largest vertical displacement value at the roof, which is 3.7 cm, with a vertical strain (%) value of 0.44%. The largest horizontal displacement value at the tunnel walls is 1.6 cm, with a horizontal strain (%) value of 0.15%. Furthermore, 3 cm is the greatest extrusion value at the tunnel face. It is clear that the tunnel is capable of effectively transferring the effective sigma 1 stresses to the surrounding rock mass based on the increase in effective sigma 1 value from the original situation before to construction to one excavation cycle. With a Safety Factor is greater than 2 (two), the initial support system in the tunnel has also demonstrated its ability to sustain static stresses throughout the construction period.