NUMERICAL ANALYSIS FOR THE IMPACT OF THE TYPE OF REPLACEMENT SOIL ON THE BEHAVIOR OF EXPANSIVE SOILS BENEATH CONCRETE STRUCTURE

Swelling soil are mainly can shrink and swell in response to moisture content changes, causing damage to structures, particularly light structures and pavement. This paper presents is looking for an answer to the question of : Dose soil replacement type affects the behavior of the foundation soil as well as the building straining action? By creating a numerical model for a six-story building constructed on expansive soil , simulated using PLAXIS 3D V22 program. Building isolated footing system is used as the foundation system in the numerical model. The natural expansive soil used in the current study possesses high values of swelling pressure, swell potential, free swell, Liquid limit, plastic limit, shrinkage limit, and Plasticity index, which are 20 kg/cm2, 38.76%, 180%, 81%, 40%, 15%, and 14%,respectively. Replacement soils of : sand ,sand:gravel (1:1),sand:gravel (1:2), sand: gravel (2:1) and gravel are used with thickness in range of 0.50m to 2.50 m to reduce expansive soil effects. Without replacement soil expansive soil causes heaving for the corner, edge and center footings by 20.73% ,19.29% and 17.88 respectively. Using replacement of : sand , sand:gravel (1:1) , sand:gravel (1:2), sand: gravel (2:1) and gravel with .thickness of 1.5 m decreased footing heave by about a percentage of 15% , 14% , 13%, 14% and 13% respectively. Replacement soil decreases the heaving of foundations , though it doesn't return the heaving to its pre-swelling value .