Numerical Modelling of Bamboo Geogrid Reinforced Fly Ash Walls under Applied Uniform Loads

This paper presents a numerical modeling to simulate the response of the experimental model studies conducted on bamboo geogrid reinforced fly ash walls under applied uniform load. Fly ash is a nonplastic and cohesionless material that has been considered as a waste, and it is a major concern for countries like India related to shortage of land for its disposal. In this regard, an attempt has been made for proper utilization of fly ash in a massive amount in the field of geotechnical engineering. The present study proposes fly ash as an alternative material to conventional soils to retaining wall applications as a backfill, and bamboo geogrid as a reinforcement. A series of experiments on reinforced fly ash model walls that comprise bamboo geogrid as a reinforcement under applied uniform loads has been conducted. The deformation behavior of the reinforced fly ash walls was studied systematically by considering a vertical spacing and varying the reinforcement length from 0.35 to 0.85 times the height of the model wall (H). The bamboo geogrids were placed in the testing tank in five layers in the form of bamboo geogrid strips. It was observed that the inclusion of bamboo geogrid strips improved the overall performance of the wall due to the confinement effect of the bamboo geogrid strips utilized as a reinforcement as compared to the unreinforced cases. In addition to that, as the length of reinforcement increases from 0.35 H to 0.85 H, the failure surcharge pressure and the facing deformation increase. However, for a particular surcharge load, increasing the reinforcement length decreases the facing deformation. This is attributed to the ability of longer reinforcements in load transfer mechanism and redistribution of the stresses in a wider area. Plaxis 3D has been used for the numerical simulation of the model experiments. The fly ash was modeled as linear elastic perfectly plastic material with a Mohr-Coulomb failure criterion, and the bamboo geogrid was modeled as an elasto-plastic material. Plaxis 3D overpredicts the horizontal wall movement, especially for longer reinforcements. However, it predicts the normalized settlement versus normalized failure surcharge pressure quite accurately.