بهمن نیرومند

Rammed aggregate piers system is one of the simple, fast and economical methods for improving all kinds of soils, especially clay and loose soils, which has become popular Two decades ago. The main advantage of these piers is to increase resistance parameters and lateral stresses of the soil around the piers, due to ramming and compacting of aggregate materials and increase the consolidation rate due to high permeability of the materials. Due to complicated mechanism of stress transfer in the soil around the piers in this method, so far, little effort has been made to determine the tensile load capacity of these piers by numerical modeling. Since, further attention and study on application and efficiency of Rammed aggregate piers as an economic solution and a method of improvement to improve the properties of fine-grained soils is required. This research presents a comparative study on behavior of Rammed aggregate piers and cast-in-place concrete piers under uplift loads by numerical modeling method. Finite element method and PLAXIS software are used for numerical modeling of the piers. Also, for modeling the behavior of Rammed aggregate piers and surrounding soil, the hardening soil model has been used with parameters derived from local experiments. The results of the modeling have been compared with previous local results in Bushehr port and the effect of length increase on load and settlement capacity of both types of piers has been studied, which shows a good correspondence between values predicted by the model and the measured values in that location Accordingly load ratio at design limit rammed aggregate piers to concrete piers in corresponding condition is on average 1.36. In rammed aggregate piers, by increasing the length of piers and transform the shear behavior of piers to bulging behavior, the tensile capacity ratio increases, which indicates the higher performance and efficiency of this group of piers than the concrete piers. Also, based on the results