Experimental and 3D numerical analysis of embankment on soft soil improved with cement bottom ash columns

Bottom ash (BA) is a byproduct produced during coal combustion and can be utilized in mortar as a column material to conserve natural resources and promote sustainable ground stabilization. In this paper, the load-carrying capacity performance of the embankment resting on cement bottom ash columns (CBAC) improved ground was examined. Physical model tests and numerical analysis were conducted for the soft soil improved with three columns spacing to diameter ratios (s/d) of 1.8, 2.4, and 3.6 and two columns length to diameter ratios (L/d) of 6 and 8. Three earth pressure transducers, load cell, and pore water pressure transducer were employed to measure the applied vertical stress on the bottom and top of the column and surrounding clay, embankment surface, and excess pore water pressure (u′), respectively. The findings obtained from both physical and numerical models demonstrated that ultimate bearing capacity (q_ult) increased by reducing the s/d and increasing the L/d values. The q_ult increased by almost 1.15, 1.39, 1.70 times and 1.18, 1.44, and 1.77 times as compared to the unimproved soil for the s/d of 3.6, 2.4, and 1.8 with L/d values of 6 and 8, respectively. The maximum improvement was achieved for the model with CBAC having L/d of 8 and s/d of 1.8. In addition, a mathematical equation with R² of 0.999 was established for the determination of the predicted q_ult. The results of this paper can lead to the usage of BA as a green material in the column for ground stabilization.