Numerical Studies on the Reinforced Fly Ash Wall in Tiered Configuration

This paper presents the findings of the numerical studies performed on a two-tiered reinforced fly ash wall. Fly ash was used as backfill material and jute geotextile was used as reinforcement as well as facing material. Wrap-around facing was used in which the jute geotextile was folded at the face. Three-dimensional models of fly ash walls showing offsets at varying distances between the two tiers and the length of reinforcement were prepared. The horizontal displacement on the wall face, tensile forces on reinforcement, and settlement behavior of the backfill wall were analyzed. Further, the wall model was scaled 10 times to generate large-scale fly ash models to understand the behavior of a life-size reinforced fly ash tiered wall. The displacement in the horizontal direction at the face of the wall reduced with the increase in length of the reinforcement and the distance between the tiers. The influence of the offset distance between the tiers on the tensile forces acting on the reinforcement was also investigated. The critical distance between the offsets was identified as 0.6 times the lower tier height. The tiered wall in the present study showed significant reduction in mobilized tensile force in the reinforcements especially at the lower tier as compared with a single (without tier) reinforced fly ash wall of the same height. The maximum tensile force for a single wall was observed to be 1.25 times and 5.35 times the two-tiered wall with D/L = 0.6 for upper and lower tiers, respectively, where D = distance of the offsets between the two tiers and L = height of lower tier. The safety factors were determined by using strength reduction factors. The factor of safety increased with an increase in the offset distance. Similar trends were observed for large-scale models.

Jute geotextile reinforced fly ash models were analyzed using finite-element analysis. The results are relevant for the construction of fly ash wall reinforced with jute geotextile. The distance between the offsets was varied and a critical distance between the offsets was identified as 0.6L. The practical implication of the study is a reduced offset distance. The previous studies have identified a larger value of such distance. The current ratio for offset distance should be considered while designing the reinforced fly ash wall in tiered configuration. A change in position as well as value of tensile force acting on reinforcement was observed with the change in the distance between the offsets, thereby changing the location of failure plane. This should be taken in to account while designing the reinforcement for the wall.