Axial Pullout Resistance and Interface Direct Shear Properties of Geogrids in Pond Ash

Presently, pond ash is accumulated in large quantities in thermal power plants. There is potential for large-volume utilization of pond ash as a fill material. Applications involving mechanical stabilization of fills constructed with geogrid-reinforced pond ash is explored in the study. A systematic experimental program was carried out to evaluate the interface direct shear strength and axial pullout resistances of four to eight different uniaxial polyester geogrids embedded in pond ash. Geogrids of varying tensile strengths and opening area ratios were considered. No significant difference in the interfacial shear strengths was observed among the four different geogrids tested. Based on the interface direct shear strengths at peak and critical states, the efficiencies of geogrids were found to range from 62 to 83%. The axial pullout resistances of geogrids in pond ash were found to be high for grids with high tensile strength. Finally, based on extensive pullout test results, empirical equations were fitted to estimate the axial pullout resistance of uniaxial geogrids embedded in pond ash corresponding to two front-end axial pullout displacements of 30 mm and 60 mm. The proposed equations were found to agree very closely with the experimental results (R² = 0.95).