Numerical Study of Deep Excavation Deformations by Iranian Top-Down Method (Case Study: Niayesh Parking)

One of the novel methods for stabilization of deep excavations is the use of top-down method. In this method, while reducing the execution time and controlling the deformation of the excavation wall, the necessary conditions for constructing structures in limited spaces or crowded urban areas are provided. In this paper, the Iranian top-down method is introduced. In order to evaluate this method, horizontal and vertical deformation of Iranian top-down is compared with diaphragm wall top-down method and nailing method. Diaphragm wall top-down with a wall thickness of 0.45 m, Iranian top - dawn with two different wall thicknesses of 0.45 and 0.65 m and  Nailed pile wall method with 0.45m thick wall, is studied numerically by using the finite element software MIDAS GTS NX. Niayesh parking lot in Tehran with a depth of 29 m is select for the case study. The results of this research show that Iranian top-down has a 20 - 25 percent lower horizontal deformation than the diaphragm wall top-down. Nailing method has three to four times more deformation compared to both types of top-downs and their difference increases by increasing the depth of excavation. The greater thickness of the wall in Iranian top-down has a negligible impact on the deformations and the effect can be ignored. Also, in Iranian top-down the ground surface settlement is 10 - 15 percent less than diaphragm wall top-down. The new method mentioned here shows that the construction of the diaphragm wall in a few steps can lead to reduction of deformations.