Analysis of a foundation system proposed to mitigate the differential settlement in soft ground

A method is proposed to analyse the foundation system recently proposed to mitigate the large differential settlement observed between the box culvert and the approach road. The foundation system is composed of cement columns reinforced soft ground overlaying a soil-cement slab and the three stabilized layers placed on the slab. The quasi-static type traffic loading, arises from the wheel load, is considered to act on the surface. Idealization of the foundation system is made in a systematic way in order to obtain a simple solution. To express the response function of the foundation system, an integro-differential equation recently proposed by Poorooshasb et al. (1996) to solve a class of geotechnical problems is used in conjunction with the formulations required to obtain the bending moment in the slab. Predictions are made for a range of parameters to obtain the influence of slab thickness, total thickness of top three stabilized layers and the spacing of columns on the surface settlement and the maximum bending stress in the slab. The results reveal that as the slab thickness and the total thickness of top three stabilized layers increase, the bending stress in the slab and the differential settlements on the surface decrease. The influence of the spacing of columns is also evident. It can be inferred that based on the allowable bending stress in slab, the economical design of such system can be obtained by assigning the optimum values of the thickness of top three layers, slab and the spacing of columns.