Laboratory Investigation of the Effect of the Geotextile Placement Pattern on the Bearing Capacity of Footing on Reinforced Sand

This paper presents the results of an experimental study on the effect of the pattern of reinforcement placement in reinforced soil on the bearing capacity of a strip foundation. A steel box filled with sand with the dimensions of 100×25×30 cm (Length, widths, and height) was used as the test base. The strip footing was simulated by a steel plate with dimensions of 25×7.5×2 cm. The sand used in this study was a poorly graded sand (SP) according to the unified soil classification system. A woven type geotextile was used as reinforcement. The effect of the reinforcement’s placement pattern on the bearing capacity of the foundation was investigated with nine different layouts including single, double, and three-layered reinforcement layouts. All the specimens prepared with a similar initial unit weight and void ratio. The tests conducted using a displacement-controlled loading device. The loading was applied with a rate of 1 mm/second. All the tests repeated at least three times to assure the accuracy and the repeatability of the results. The results of these tests indicated that the bearing capacity of the foundation increases as the length of the reinforcement increases but up to a certain limit and then remains constant. Although increasing the number of reinforcements layer increased the bearing capacity of the foundation, however, the effectiveness of the geotextile in the improvement of the bearing capacity decreased. Placement of the reinforcements in a discrete pattern improves the effectiveness of the reinforcement on the bearing capacity improvement. In multi-layer reinforcement layouts, using discrete strips of reinforcements in each elevation without overlapping with upper- and lower-layers of reinforcements, resulted the maximum efficiency of reinforcements influence in the improvement of the bearing capacity of the foundation. In the recent case, for a specific cross-sectional area of the reinforcement, the bearing capacity of the foundation could be increased by 20% using 17% less reinforcement. The results of this study indicate that the layout of the reinforcement pattern is a very important factor in the bearing capacity of foundations on reinforced soil. With a proper placement of reinforcements, the maximum bearing capacity of the foundation could be achieved with a minimum amount of reinforcement material.