Tunnel Monitoring during the Excavation Phase and Cost Optimization - a Case Study of Hakim Tunnel

Submitting of a geological model, design parameters estimation, excavation and support system choosing with minimum risk, safety providing and cost reduction are major challenges for tunnel construction process in complicated ground conditions. Therefore, sufficient prior studies, interpretation, analysis, and process of data in an updatable model in order to planning for construction process are important in a tunneling project. Hakim Expressway one of the capital's main highways in Tehran metropolis with 9 Km in length, starts from the junction of Resalat Expressway and Kurdistan Expressway after Resalat Tunnel and ends in Lashgari Expressway. The west extended this highway passing through the area of Forest Park Chitgar. Due to environmental constraints, the Hakim twin tunnels with cross-section of 186 m2 excavation areas and total length of 3256 m to the NATM/SEM method in this area were excavated. During tunnel excavation using field observations, the results of the monitoring and reviewing the geological model, ground behavior and classification were re-examined to optimization of the excavation and support class. Optimization plan resulted in a 10 percent savings in construction costs.