Some studies on the load carrying capacity of shallow foundation resting over geogrid-reinforced sand under eccentric load

Abstract

Several works have been done relating to the estimate of the ultimate bearing capacities of shallow foundations, supported by geogrid reinforced sand. Few experimental studies have been made on the evaluation of bearing capacity of shallow foundations on geogrid-reinforced sand under eccentric load. These studies relate to strip and a square foundation is yet to be done. The purpose of this thesis is to conduct few model tests in the laboratory by using square surface foundation over the reinforced sand bed. The model footing used for the model tests in the laboratory is of size 10cm x 10cm. The average relative density maintained during all the tests is 69%. The reinforcing material used in the experiment is SS 20 in 2, 3 and 4 number of layers. The load eccentricity is varied from 0 to 0.15B with an increment of 0.05B. The vertical distance of first geogrid layer from base, distance between the consecutive geogrid layers, and width of the geogrid has been kept constant. For each set up load intensity and corresponding settlements are observed which are plotted to get load-settlement curves for each set up. The load-settlement curve for each test is plotted to determine the ultimate bearing capacity. Parametric studies have been made to evaluate the influence of load eccentricity on bearing capacity of the foundation. The ultimate bearing capacity of eccentrically loaded square footings can be computed by knowing the ultimate bearing capacity of square footing under central load and a reduction factor (RkR) for reinforced condition. The reduction factor is developed based on the results of laboratory model tests on geogrid reinforced soil. The existing data base of Patra et al. (2006) is used for predicting bearing capacity of strip footings over geogrid reinforced soil under eccentric load by using Artificial Neural Network (ANN).