Experimental and Numerical Modelling of Inclined Pullout Behaviour of Geosynthetic Sheet used as Veneer Reinforcement

There is immense public pressure to close the waste dumps in India, most of which have far exceeded their capacity. Since these dumps usually have a nearly vertical configuration, with little space at the toe for flattening of slopes, veneer reinforcement is provided to stabilise the multi-component cover systems. This study presents the results of the experimental and numerical investigations conducted on geosynthetics of sheet-form used as veneer reinforcement in landfill covers to investigate the influence of pull inclination on anchorage capacities. The geosynthetic sheet was anchored in three types of anchors: run-out, I-type, and L-type. Inclined pullout tests were conducted using an inclined pullout device developed in-house. The geosynthetic sheet was manually fabricated by arranging the longitudinal ribs extracted from a geogrid of 60 kN/m ultimate tensile strength. The model tests were simulated using three-dimensional finite element analyses software PLAXIS 3D. The geosynthetic behaviour was modelled with bending/‘plate’ elements instead of conventionally used axial/‘geogrid’ elements.

The experimental and numerical results demonstrated the positive effect of the vertical component of the inclined pullout force: a 22% increase in maximum pullout resistance on increasing pull inclination from 0° to 30°. The results also show that the I- and L-type anchors provide approximately 50% and 95% more pullout force than the run-out anchor, respectively. The numerical results showed that the new approach of modelling geosynthetics using ‘bending’ elements could satisfactorily capture the peak inclined pullout behavior. However, the post-peak response was not satisfactorily modelled due to the inability of Mohr-Coulomb constitutive relationship in capturing the post-peak strain-softening response.