Construction Test and Numerical Analysis on Reinforcing Bar Insertion Method Prestressed Before Grout Hardening for Natural Slopes

Slope failures frequently occur during rainfall, earthquakes, and long-term weathering, and reinforcing bar insertion is widely used worldwide to prevent such failures. In this method, steel bars are installed in pre-drilled holes and bonded to the ground with grout, with a pressure plate resisting deformation; however, tensile forces generated during slope movement may crack the hardened grout and reduce performance. To address this issue, we propose an Early-stage Prestressed Reinforcing Bar Insertion Method, in which tensile load is applied to the bar before grout hardening. Grout is injected while maintaining tension, allowing the bar to remain prestressed after construction and inducing compressive stress in the grout, which is expected to improve resistance against tensile loading. A field construction test and numerical finite-element analysis were conducted to verify performance. The test confirmed constructability within half a day and retained tensile force of 42 kN after 30 days. The numerical model reproduced measured axial forces and indicated that the hardened grout remained in compression, with an average compressive stress of 3680 kN/m2. These results demonstrate that prestressing can enhance grout tensile resistance. The method shows promise for future application and potential extension to similar anchoring systems.