BEHAVIOR OF GEOCELL REINFORCED SAND FOUNDATION SYSTEMS UNDER CYCLIC LOADING

Geocell is an efficient type of reinforcement in the soil improvement problems as a result of the lateral confinement it provides for the infill soil. However, its applicability is not well considered in practice due to the lack of a standard design method. In this research, in order to study the monotonic and cyclic behavior of geocell reinforced sand, a reduced scale physical model of foundation on the reinforced soil is developed and pressure-settlement performance of the foundation system is evaluated. Geocells with various heights are made using a woven geotextile which are located in the optimum position in the dense sand bed and the strip foundation model is then situated on the surface of the reinforced soil. The footing is then subjected to a prespecified static load followed by 1000 cycles of repeated loads with the frequency of 0.5 Hz. The results show that cyclic loading leads to substantial plastic settlement in each cycle which have a decreasing trend by increase in the load cycle number. Depending on the type of reinforcement and the amplitude of the cyclic load there would be footing instability after some load cycles i.e. ratcheting happens or a stable condition in which development of plastic settlement will be ceased by exerting the cyclic load i.e. plastic shakedown occurs. It is concluded that the cellular geotextile improves the performance of the footing much more than the planar geotextile with the same amount of reinforcement. Increasing height of geocell will also result in more improvement factors in reducing the permanent plastic settlements and the amplitude of the cyclic loading and its difference with the ultimate static bearing capacity of the footing makes a significant contribution on the behaviour of the reinforced sand foundations.