Design method for active slope reinforcement: A case study of excavated slopes

Objective Slope instability and failure exhibit extinct spatiotemporal characteristics. Existing design methods for passive reinforcement have resulted in the engineering instability of numerous excavated slopes. Therefore, analyzing the spatiotemporal evolutionary patterns of slopes during excavation and exploring the design methods for active slope reinforcement are particularly important for the information technology (IT)-based construction and safety control of slopes.

Methods Using on-site investigations and numerical simulations, this study analyzed the causes of excavation-induced failure of high slopes, as well as the evolutionary pattern of the principal stresses in the sliding zone. Consequently, this study revealed the progressive failure mechanism of slopes during excavation and developed a design system for active slope reinforcement with reinforcement timing, depth, and force as key factors. Finally, this study verified the feasibility of the system using typical slope excavation engineering.

Results and Conclusions  The results indicate that the excavation-induced failure process of a slope can be divided into three periods: the incubation, stable development, and rapid development periods of failure stress. The characterization of the deformation stage and safety factor (F_s) of the excavated slope using the excavation steps was established, revealing that the optimal reinforcement timing was the time when 1.05≤F_s≤F_st (design safety factor) in the controllable elastic and plastic deformation stage. The reinforcement timing can be more conveniently determined using the calculation method for the critical slope height, which indicates that 0.4‒0.7 H_cr (critical slope height) represents the optimal reinforcement time. The method for determining the upper and lower boundaries of the active reinforcement depth indicates that the depth of the anchorage segment should be positioned below the upper boundary of the anchorage segment and extend to its lower boundary. Considering the compensation for excavation-induced stress loss, this study proposed a method for determining the active reinforcement force of each grade of a slope to ensure slope stability during excavation. The comparison of active and passive reinforcement designs for an engineering case suggests that the proposed design method for active reinforcement allows for the effective restriction of slope deformations and plastic zone expansion using a relatively small reinforcement force. The results of this study can serve as a guide for the IT-based construction and reinforcement design of slope excavation engineering.