دانلود رایگان مقاله انگلیسی مدل سازی عددی فونداسیون سطحی بر روی خاک روانگرا تحت بارگیری سینوسی - اشپرینگر 2018

Abstract

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 9.55 cm and 4.20 cm respectively. When shear modulus increases from 8 to 20 MPa, the settlement decreases from 9.55 cm to 2.47 cm in vertical direction and 4.20 cm to 0.98 cm in lateral direction. Excess pore pressures increases with the depth and decreases with the increases in shear modulus.

7 Conclusions

The numerical analysis of shallow foundation in cyclic loading conditions has provided valuable understandings regarding the evaluation of liquefaction-induced foundation settlement and effect of pore water pressure which is primarily controlled by shear modulus, permeability and intensity of earthquake. A maximum vertical settlement of 9.5 cm and horizontal displacement of 4.2 cm are observed at right of the footing surface of the soil domain. At higher value of shear modulus (G = 20 MPa), liquefaction does not occur within the soil domain except at Z/B = 0 and 0.5. As the shear modulus is reduced, liquefaction of soil is observed because of higher displacement and excess pore pressure. It is also observed that maximum stress ratio q/p is 0.98 at the depth ratio of Z/B = 0.25, which declines with depth mainly due to effect of initial effective stress. This results in development of higher excess pore pressure at shallow depth. Permeability also plays important role, if the permeability is low generation of pore water pressure is high so chance of liquefaction increases.