Effect of Coal Ash–Geogrid Interaction on Static and Dynamic Behavior of Ash-Filled MSE Walls

Use of mechanically stabilized earth (MSE) is known to improve the static and seismic performance of highway retaining walls, bridge abutments, dams, and levees. The stabilization of the earth is generally done by placing reinforcing elements such as metal strips, geosynthetic layers, or micro-piles in different layers of the backfill soil. The general convention is to prefer granular soils over cohesive soils as backfills due to their better drainage and lower shrinkage-swelling potentials. Nowadays, as an economic alternative, utilization of coal ash as a backfill material in MSE walls is being widely explored. Coal ash being a lightweight material with better drainage characteristics than cohesive soil poses several potential benefits in terms of static earth pressure, swelling issues, and dynamic inertia. However, the response of this coal-ash-filled MSE walls when subjected to dynamic loads is a topic that demands further investigation. The primary challenge is to select a constitutive model and define its parameters in a manner, by the virtue of which nonlinear and cyclic behavior of coal ash can be simulated. Moreover, since studies emphasizing the modeling of interaction between ash fill and reinforcing material are limited, there is scope for exploration in this direction. In this context, the present study focuses on developing a robust and reliable numerical model using discrete finite element approach which addresses these two issues for static and dynamic loading case. The model has been validated with results in existing literature. The performance of the wall has been assessed in terms of important response parameters such as lateral displacement, acceleration response, and the strain levels in the reinforcement layers at the end of the construction and during a seismic event.