Numerical study of pullout capacity of Helical multiple anchors for supporting excavations

Today there are numeral methods for supporting an excavation. Using of helical multiple anchors as excavation support has speared recently. Because of wide range of applications of helical anchors, a massive number of experimental, numerical, and field studies have been carried out. This study works on the pullout capacity of helical multiple anchors by using FLAC 3D software. First, a verification test is carried out in order to confirm the method of simulation. Then, with the help of an extensive parametric study, the effect of different parameters on pullout capacity is observed. This study indicates that sharp growth in loading capacity is observed due to an increase in density of soil and diameter of helical plates. In addition, the results show that changes in the cohesion of soil have a few effects on the loading capacity of helical anchors. Moreover, the share of loading on the plates keeps remain if the space between plates is five times of helical plate diameter and more. In this situation, the failure mechanism is individual plate. Nevertheless, if the space between plates is less than five times of helical plate diameter, the share of loading on the first helical plate (near to excavation) goes up, but the share of loading on the rest helical plates drops dramatically. In this situation, cylindrical shear is the main failure mechanism. Therefore, the current study results demonstrate that the critical space between helical plates is five times of helical plates diameter.