Numerical Study of Eccentrically Loaded Strip Footing Resting on Reinforced Sand by Using PLAXIS 2D Software

الملخص

Abstract

The present paper aims to evaluate the performance of bearing capacity of eccentrically loaded strip footing supporting on unsymmetrical geogrid reinforced sand. More specifically to study the behavior of such eccentrically loaded strip footing supported on sand at different relative densities (dense, medium, and loose) reinforced with nonsymmetrical geosynthetic layers. A numerical study of the behavior of an eccentrically loaded strip footing resting on symmetrical and unsymmetrical geosynthetic reinforced sand is done. Particular attention was given to simulate strip footing constructed on unsymmetrical geogrid layers with eccentricity in one direction of the strip footing. Several configurations of geogrid layers such as different number (N), length (L), geogrid layer eccentricity (e_G) along with the effect of the sand relative density (R_d), the average unit weight (γ), and the load eccentricity (e_L) were investigated. The numerical study on a plane strain prototype strip footing was performed using finite element analysis PLAXIS 2D software. Tests results indicate that the strip footing performance could be appreciably improved by the inclusion of unsymmetrical geogrid layers leading to an economic design of the footing. However, the efficiency of the sand-geogrid system is dependent on the load eccentricity ratio (e_L/B) and several reinforcement parameters such as number of reinforcement layer (N), length of reinforcement (L), and eccentricity of reinforcement layer (e_G). The ultimate bearing capacity improvement due to the soil reinforcement and without reinforcement was represented using q_u(R) and q_u(UR)   respectively.

Therefore, it is useful to use the unsymmetrical layer of geogrid with eccentric load, and the appropriate value of geogrid eccentricity is (e_G=0.08B) that gives rate of improvement in the bearing capacity about 13.77% comparing to bearing capacity of the soil when laid the geogrid layers symmetrically beneath the strip footing, and, the percentage of improvement in the bearing capacity of the soil is up to 97.14% comparing to the soil bearing capacity without reinforcement. Also, the optimum length of reinforcement is equal five time of the footing width (L=5B), and the optimum number of reinforcement layers are four layers (N=4),

Keywords: Bearing capacity, Eccentric loads, Eccentric geogrid, Reinforced sand, Strip footing, Finite Element Method, PLAXIS 2D