Numerical Modeling of Shallow Foundation on Liquefiable Soil Under Sinusoidal Loading

In seismic areas, most of the light and heavy structures resting on saturated soil are prone to liquefaction behavior. It occurs in the form of cyclic mobility of soil mass, reduction in bearing capacity, increment in lateral pressure and settlement of structure which must be inspected before constructing any civil engineering structures so that respective precautionary measures can be taken at early stage. The aim of this paper is to model the behavior of shallow foundation on liquefiable soil using Biot's basic theory of porous media. The non-linear behaviors like dilitancy, loading-unloading, hardening and other behaviors of the soil mass are modelled using Pastor-Zienkiewicz Mark III model. Generalized Newmark-beta method is employed for integration in time. A computer code based on finite element method is developed in FORTRAN 90 to simulate a surface footing resting on loose liquefiable soil deposit. The models is subjected to input ground motion of sinusoidal nature to observe the settlement, excess pore pressures, and liquefaction susceptibility of the soil deposits. Some of the key parameters like soil permeability, shear modulus and contact pressure has been also explored on foundation response during numerical study. The results show that settlement of foundations increased with the increase of soil permeability i.e. at higher permeability, maximum settlement in vertical direction and lateral direction are 9.55cm and 4.20cm respectively. When shear modulus increases from 8 to 20MPa, the settlement decreases from 9.55cm to 2.47cm in vertical direction and 4.20cm to 0.98cm in lateral direction. Excess pore pressures increases with the depth and decreases with the increases in shear modulus.