Pullout behavior of biocement–geosynthetic reinforcement system: a parametric study

In the biocement–geosynthetic system, biocement is combined with geosynthetic to increase the pullout resistance of the geosynthetic and thereby the stability of reinforced soil structures. In this work, several pullout tests were conducted to evaluate the various influential factors for the BG systems, including the biocementation factors such as number of treatment cycles, concentration, and volume of biocement solution, and other factors such as normal pressures, relative densities of soil, and geosynthetic types. The pullout test results revealed that the performance of the BG systems increased with the number of treatment cycles and, to lesser extents, with increases in the concentration and volume of biocement solution. It was identified that the higher interface shear strength was mainly due to the higher calcium carbonate content around the geosynthetic. Hence, for biocementation factors, the most efficient way to improve the performance of the BG systems is to increase the number of treatment cycles. Additionally, the pullout resistance of the BG systems increased with the normal pressures and relative densities of the sand. Furthermore, under the same test conditions, the pullout behavior of the biaxial geogrid BG system was found to be better than that of the geosynthetic strips BG system. Overall, the data presented in this study could be used as a reference to improve the efficiency of the BG systems and further strengthen the stability of reinforced soil structures.