Model studies on encased fly ash column-geocell composite systems in soft clay

This study narrates the use of postconsumer waste plastic water bottles for developing a new type of encasement to confine fly-ash columns fully penetrated in soft clay. Geocell-reinforced fly-ash beds along with a jute geotextile separator were also placed over the fly-ash columns, while the cellular mattresses were also made of the same type of plastic water bottles. A series of systematic model tests were carried out on encased fly-ash columns, geocell composite systems, and encased fly-ash column-geocell composite systems in soft clay, while the three different systems produced improved footing capacity of about 5-fold, 8.5 times, and 12-fold, respectively, as compared to the untreated clay bed. It was observed that with the increase in mattress height over the encased fly-ash column, the contribution from the encased column decreased accompanying the higher contribution from the geocell mattress in the overall footing capacity over the encased fly-ash column-geocell composite systems. Moreover, model tests were performed on groups of three and four end-bearing encased fly-ash columns in triangular and square patterns, respectively, to determine the efficacy of the proposed plastic bottle encasement in a group column situation. The group of four columns showed better footing capacity than that over single columns and the group of three columns.