Effect of isolated footing on fly ash subgrade reinforced with PET bottles: An experimental and analytical study

Abstract

The continuous and significant excavation of subsurface soil and rock for structural backfilling, impacts the environment negatively. The present study attempts on the exploitation of non-biodegradable and hard-to-dispose waste materials (in different capacities) such as fly ash (FA), rock quarry dust (RQD), and refurbished Polyethylene Terephthalate (PET) bottles were used as an alternative for structural backfill and reinforcement. For model testing, two phase novel methodology was proposed (Unreinforced and reinforced FA system). A total of 29 systems were examined, encompassing a broad range of boundary conditions like FA subgrade system, unreinforced FA system (FA + RQD) with varying RQD layer thickness “H”, and reinforced FA system (FA + RQD with PET bottle mattress as an interface between the FA subgrade and the RQD layer). The parameters pertaining to the reinforcement (width “b”) are varied with respect to the constant value of “H”. Loading was applied on isolated footings for both phases. The model testing demonstrates that the performance of footings resting on RQD laid over stabilized FA subgrade with PET bottle mattress as an interface outperforms other systems significantly. Optimum values for boundary conditions were obtained in case of both the systems. It is observed that in case of reinforced FA system with optimum boundary conditions, the bearing capacity was increased by 10 % and the RQD layer’s thickness was reduced by 47 % as compared to optimum values of an unreinforced FA system. Further, the optimized values of the phases were validated by using PLAXIS 3D software.