Numerical Study of the Failure Surface in Granular Soil Under Two Closely Spaced Strip Footings

Author(s):  
Assma Benbouza ◽  
Liela Arabet ◽  
Khelifa Abbeche
Author(s):  
Nasser A. A. Radwan ◽  
Khaled M. M. Bahloul

The aim of this research is to investigate numerically the effect of using compacted sand as soil replacement layer beneath a strip footing on its bearing capacity. Finite element computer software Plaxis 2D version 8.6 was used to predict the behavior of strip footing resting on loose sand and on compacted sand. Study was conducted for footing widths of 1 up to 2 meters and various depths ranging from 1m up to 2m, also the effect of replacement layer thickness was investigated. It was found that using replacement layer beneath strip footing increases its bearing capacity for different widths and depths of footing. This improvement is observed up to thickness of replacement layer equal to 3 times the footing width (H/B=3), where further increase in replacement layer thickness does not affect significantly bearing capacity of footings.


Author(s):  
Lamia Sadek ◽  
Khaled M. M. Bahloul

The aim of this research is to investigate numerically the behavior of strip footings resting on Sabkha soil reinforced using two methods. Firstly, using a layer of compacted sand reinforced with random distributed fibers beneath footing. Secondly, using a layer of compacted sand reinforced with geogrids. The benefit of mentioned two methods on the improvement of strip footings bearing capacity and decreasing the settlement was investigated using a finite element computer program Plaxis 2D ver. 8.6. It was found that using two methods increases bearing capacity of strip footings significantly specially using first method (fiber reinforced sand layer). It was observed also that the settlement decreased for the same stress values.


2021 ◽  
Vol 31 (1) ◽  
pp. 29-43
Author(s):  
Surya Pratap Singh ◽  
Amrit Kumar Roy

Abstract This paper aims to study the behaviour of a circular footing resting on two granular layers, i.e., a dense sand layer resting on loose sand strata, subjected to a vertical and an inclined loading (α=0°, 10°, 20°, 30°) using the finite element (FE) software PLAXIS-3D. The Mohr-Coulomb criterion is employed for the analysis of the model, in which two parameters are considered to vary significantly; (1) thickness of the top layer (dense layer) and (2) friction angle (ф) of both the layers. In the circular footing, the bearing capacity on the layered soil profile is assessed using the mechanism of punching shear failure following the desired area approach. The punching shear failure mechanism formed in dense sand has a parabolic shape at the ultimate load when the maximum mobilization of shear force through the failure surface is taken into account, otherwise, the punching failure is the actual failure while punching in the lower layer continues to a greater extent, depending on the interface load. Bearing pressure decreases as the inclination increases with respect to the vertical, along with bearing pressure increasing as the thickness of the dense sand layer increases. The software results compare well with data available from the literature.


2021 ◽  
Vol 12 (1) ◽  
pp. 111-141
Author(s):  
Navneet Himanshu ◽  
Avijit Burman ◽  
Vinay Kumar

The article addresses stability analysis of complicated slopes having weak soil layer sandwiched between two strong layers. The search for critical failure surface and associated optimum/minimum factor of safety (FOS) among all potential failure surfaces can be posed as an optimization problem. Two different variants of particle swarm optimization (PSO) models, namely inertia weight-based PSO (IW-PSO) and contemporary standard PSO (CS-PSO), are used to obtain optimum global solution. Detailed comparison between the global optimum solutions obtained from two PSO variants and the effect of swarm size is studied. The performance of IW-PSO and CS-PSO are studied by observing the convergence behavior of the respective algorithms with respect to iteration count. The influence of velocity clamping on the optimized solution is investigated and its use is found beneficial as it prevents the solution from overflying the region with global best solution. The studies related to swarm diversity demonstrating the exploitation and exploration behaviors of the algorithms are also presented.


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