Assessment of the arching effect and the role of rock bolting for underground excavations in rock masses—a new numerical approach

• Published in: Arabian journal of geosciences Vol. 13; no. 13
• Main Authors: He, Shaohui, Wang, Dahai, Liu, Xiabing, Zhang, Jiawen
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.07.2020; Springer Nature B.V
• Subjects: Arches; Bolting; Bridging; Dredging; Earth and Environmental Science; Earth science; Earth Sciences; Excavation; Finite element method; Original Paper; Rock bolting; Rock masses; Rocks; Stability; Stress concentration; Stress ratio; Underground structures; Underground excavations; Ground arch; Rock bolt
• ISSN: 1866-7511; 1866-7538
• DOI: 10.1007/s12517-020-05570-w

In very jointed rock masses, the ground arch developed around the underground opening is an arch-shaped structure to maintain the excavation stability, and the rock bolting has been attributed as one of the dominant approaches to enhance the arching effect. Through 2D finite element method (FEM), numerical studies were performed to investigate the arching effect and the importance of rock bolting. Based on the distribution of the mean stress σ m , the boundary of the ground arch is determined without several limitations existed in other methods and the artificial arching effect of rock bolting could be assessed directly. Impacts of the cover depth H t , the tunnel span D , the in situ stress ratio k , and the rock mass strength (frictional strength ϕ ) were first revealed. The enhancement provided by the rock bolting were then directly evaluated through the artificial ground arch. The formation of the artificial arch is carefully studied considering the bolt spacing and the bolt length. Results show that σ m could be used as a reliable indicator to assess the arching effect. Rock bolting reinforces the surrounding rock mass and contributes to the formation of the sub-arch therein. With enough reinforcement, the sub-arch overlaps each other and a global artificial arch could form to enhance the arching effect.