New test facility for studying the behaviour of pressure-grouted soil nails

Abstract

This paper describes test apparatus developed to evaluate, at model scale, the behaviour of a pressure grouted soil nail system. The apparatus allows the grout to be injected at different injection rates. A latex membrane is used as a liner around the grouting outlets of the pressure-grouted soil nail to form a Tube-a-Manchette (TAM) for direct injection of grout into the surrounding soil, in some tests entering the soil voids. Pure cement and water were used as the grout (w/c = 0.5). A special screw jack pump system was developed, automated and instrumented to control the injection rate of the grout, as well as to monitor the injected grout volume over time. In addition, an overburden pressure system was designed to apply surcharge pressure using a water-filled rubber bag, which also allowed the settlement of the soil mass to be inferred directly from the volume of pressurized water. In this study, a series of laboratory-scale pullout tests were conducted with the newly developed apparatus to investigate the performance of pressure grouted soil nails with the grout being injected at different rates. The experimental results show that more grout can be injected at higher rates. Accordingly, the pullout resistance of the pressure grouted soil nail also increases with the injection rate.