Analysis of Interfering Circular Footings on Reinforced Soil by Physical and Numerical Approaches Considering Strain-Dependent Stiffness

Abstract

This paper numerically examines the bearing capacity, settlement, and failure kinematics of two closely spaced circular footings on reinforced soil. A number of large-scale tests are performed to identify the influence of the tilt of interfering footings on their ultimate bearing capacity and settlement, and these experimental results are used to verify the numerical model. Because the mobilization of shear strength in soil and tensile resistance in the geogrid depend to a large extent on the strain level (especially in small strains), a nonlinear elastic-plastic constitutive model in conjunction with a nonassociated flow rule is proposed. In addition, the model accounts for the dependency of the friction and dilation angles on the strain level in the plastic domain. The constitutive parameters are calibrated for the triaxial loading test, whereas the numerical model for the closely spaced footings is verified with reference to the large-scale test results. Thereafter, the ultimate bearing capacity and settlement of interfering circular footings on reinforced soil are studied for different configurations, and the critical size and position of reinforcements that maximize the bearing capacity are characterized. Results show that the ultimate bearing capacity increases up to a maximum of 40 and 90% by the use of one and two layers of geogrid, respectively. Beyond the bearing capacity, the settlement of adjacent circular footings increases up to 45% (compared with a single footing with the same safety factor). Finally, the influence of reinforcing soil on failure kinematics and soil deformation pattern is investigated.