Static behavior of ring footing based on geogrid-rubber reinforced sand bed

Ring footings have been used in various industries like oil and gas. So this kind of footings is very important and doing some works to improve their behavior, can be very important. In the present study, by using experimental tests, the behavior of ring footings with a constant outer diameter of 300 mm based on reinforced bed with granular rubber particles alone and also in combination with a geogrid layer, subjected to static loads, has been investigated. The results showed in both unreinforced and rubber-reinforced bed, the ring footing with inner to outer diameter ratio of 0.4 had the maximum bearing capacity. Also the optimum thickness of rubber-reinforced layer is equal to 0.5 times the outer diameter of ring footing; in this case the bearing capacity can be increased by 41.5% compared with the unreinforced bed; more increases than optimum value, have reverse results and lead to decrease in bearing capacity and increase in settlement. Using geogrid layer can activate reinforcing effects of rubber-reinforced layer with high thicknesses, but its value is not big enough to overcome the negative effects of using rubber-reinforced layers with higher thicknesses than optimum value. At last, using geogrid reinforcement in combination with rubber particles can be more effective than using each of them alone. In geogrid-rubber reinforced bed, the bearing capacity can be increased by 62.7% compared with the unreinforced bed.