In this study, the soil bearing capacity improvement using geobags is investigated. The bearing capacities of shallow foundations on reinforced and unreinforced soil under vertical loads are determined experimentally and numerically. Different sizes of geobags, as well as number and arrangement of geobags, were used in physical models and the load-settlement curves have been obtained. In the next step, laboratory conditions were simulated employing a 3D finite element computer code. Having validated the numerical modeling, the influence of other factors such as the scale effect on soil improvement and failure mode under a footing are investigated. Results of this study show that using geobags under footings significantly increases the bearing capacity of foundation. It was also found that the number and arrangement of geobags are the most important factors in the increase of bearing capacity and decrease of settlements of foundations.

Introduction

Geobags, soilbags; sandbags, etc. are bags usually made from textiles having high tensile strength and filled with materials such as gravel, sand and even construction wastes. Advantages of soil reinforcement by geobags summarized as follows [9]: (i) Geobags are light. (ii) Their transportation and relocation are very easy. (iii) Compatibility with the environment due to no use of any chemicals and there is no noise during construction. (iv) No special or heavy construction equipment is needed. (v) The materials inside geobags may be any granular remains and construction wastes such as recycled concrete, asphalt, tire and tile. Use of geosynthetics and geobags for protection against flood and controlling erosion of river and sea shores, especially sand beaches was known for decades [7,8]. Recently, geobags have found many other applications as temporary and permanent structures in engineering projects. Bearing capacity and settlements of shallow foundations have always been great concerns for engineers and researchers in geotechnical and civil engineering projects. The use of geobags to increase bearing capacity of soft soils is one of these new applications to increase bearing capacity and reduce settlement. Confining the soil by geobag leads to increase in its bearing capacity. This advantage has encouraged the engineers to use geobags for geotechnical improvement of sites with low bearing capacity. Building retaining walls, constructing small temporary buildings, reducing vibrations due to the movement of vehicles and earthquakes are some other applications of geobags. Hence investigations on geobags behavior are carried out in the last decades worldwide, theoretically, experimentally and numerically. The aim of this study is to investigate the role of geobags in increasing the bearing capacity of soils through a series of experimental and numerical modeling.