Numerical Modeling of Ground Improvement Methods Tehran Metro Line 6 Excavation

One of the most critical issues in weak grounds is soil improvement, which is considered reused in a new geotechnical structure or improves the current structure condition. In the present research, implementing a limited, finite element numerical method to predict the rate of ground settlement level before and after the implementation of ground improvement in the eastern access tunnel drilling process of Khorasan Square Station located in Tehran Metro Line 6. Since the tunnel route passes under residential buildings and shops, with the excavation of this part of the Khorasan Square Station project, large amounts of settlement exist on the ground surface, which cracked buildings and shop structures. Based on this, piling, fore poling, and anchoring improvement methods can be used for loose and fallen grounds that were modeled numerically by MIDAS GTS NZ software. In this research, in addition to investigating the performance of the mentioned methods, the effect of geometric parameters, including the covering of fore poling pipes, pile length, and the diameter of anchors, was investigated. The criteria for investigating, the Displacement occurred at ground level, and tunnel crown is considered. Results showed that all methods have been useful in reducing ground settlement and tunnel crown. Also, Among the above-mentioned improvement methods, the method of using the fore poling method with anchorage has reduced the plastic points surrounding the tunnel and also has a greater effect in reducing the settlement of the ground, so that it has reduced the maximum settlement of the ground surface by 50%.