An experimental study on the load settlement behavior of a fiber-reinforced sand bed

Abstract

The ultimate bearing capacity of a strip footing resting on sand reinforced with randomly distributed fibers overlying poorly graded sand has been investigated. In this study, sand was reinforced with 1% randomly distributed synthetic fibers of 6 mm length and the top reinforced layer was separated from bottom unreinforced layer with the help of jute fabric. The effect on pressure-settlement characteristics were plotted for a footing under plain strain conditions resting on sand reinforced up to 0.5 <i>B</i>, 1.0 <i>B</i>, 1.5 <i>B</i> and 2.0 <i>B</i> depths below the base of the footing of width <i>B</i>. Numerical modeling of the results was carried out using a finite element based software GEO STUDIO - SIGMA/W. Pressure-settlement characteristics were studied by conducting model tests on 0.10 m wide footing under plain strain conditions and it was concluded that reinforcing the top layer with 1% randomly distributed fibers increases the bearing capacity and reduces the settlement. Model tests results show that there is up to five times increase in bearing capacity of footing, resting on sand, if the top layer of sand is reinforced up to 1 <i>B</i> depth and up to eight to nine times increase in bearing capacity if top layer is reinforced up to 2 <i>B</i> depths. Experimentally, the values of settlement for virgin soil decrease up to 77% and analytically these decrease up to 69% when soil is reinforced down to a depth of 2 <i>B</i>. For a footing of size of 1 m, resting on the same sand as has been used for model tests; analytical results show an increase in allowable bearing capacity of 2.7 times that of unreinforced sand after reinforcing the top 1m (1 <i>B</i>) soil with randomly distributed fibers.