ABSTRACT
In this paper the load-settlement of gypseous soils improved by microbial induced calcite precipitation (MICP) have investigated experimentally and numerically. Tests were carried out on two sandy soils collected from two different sites in Iraq, Najaf city and Samawa city. The soil samples were injected with two ratios of bacteria solution (4 and 8%). The load-settlement of gypseous soils were investigated in both cases dry and soaking. A numerical model is developed using PLAXIS software. Finite element analysis is carried out using Mohr coulomb failure criteria to represent 2D soil model. Foundation is modelled as square footing and load increment is applied till the soil model fails. Ultimate bearing capacity is identified as that minimum pressure on footing at which the foundation soil experiences shear failure. The stress distribution in soil and displacement experienced at different locations are obtained. Also, the ultimate bearing capacity of square foundation was computed by Terzaghi’s equation to know the preliminary values of bearing capacity of gypseous soil and loading frame which was successfully compared with PLAXIS software. Based on the results of tests, PLAXIS software can be used worthily to understand the load-settlement behavior of gypseous soils in dry and soaking conditions and Mohr-Coulomb model can be considered the best to estimate the ultimate bearing capacity of a foundation constructed on gypseous soils. The difference between the maximum settlement measured from experimental tests and calculated from the numerical analysis was 20% in dry condition and 30-40% in soaked condition. The bearing capacity obtained from experimental tests were identical with results of Terzaghi’s equation.
