The effect of using gravel columns on seismic behavior and improving loose soils

Increasing the bearing capacity of foundations in loose substrates has always been one of the main concerns of geotechnical engineers. One of the methods of stabilizing this type of soil is the use of gravel columns. Due to the limitations in use of piles and deep foundations, one of the best and most economical options is to improve and strengthen soft clay, silty and loose sandy soils in order to use shallow foundations, the effectiveness of which depends on the parameters. In this research, it has been tried to investigate the behavior of a group of gravel columns with different numbers and arrangements using three-dimensional dynamic correlation analysis. For this purpose, using Abaqus software, the behavior of the gravel columns as a group in the loose soil profile, under earthquake force and lateral pressure due to lateral expansion has been evaluated. Also, the values of ground acceleration at the soil surface have been studied and analyzed. In this study, a total of ۵ models have been made according to different geometries and in all models, the dimensions of the soil are in the form of a cube with length, width and height of ۲۰ by ۲۰ by ۲۰ meters. The results showed that regardless of the condition of the reinforcement, surface settlement always increases with increasing the number of settling cycles, so that the records that had a longer time created more settling in soft soil. If gravel columns are used in all conditions and under any record, the amount of subsidence and strain in the soil will be reduced. Reinforcement is not very effective in the intensity of smaller cyclic loads, and if the appropriate volume and dimensions of gravel columns are used, the settlements will have an acceptable reduction. Finally, it was found that increasing the number of sand columns has a significant effect on improving seismic behavior and reducing surface subsidence of soft soils reinforced with dense gravel columns. However, increasing the diameter of the columns has little effect on reducing subsidence and improving the seismic behavior of soft soils.

Keywords:

Dense gravel columns , numerical modeling , soil subsidence , bearing capacity , seismic behavior