Energy analysis of rock plug thickness in karst tunnels based on non-associated flow rule and nonlinear failure criterion

• Published in: Journal of Central South University Vol. 24; no. 12; pp. 2940 - 2950
• Main Authors: Yang, Zi-han, Zhang, Rui, Xu, Jing-shu, Yang, Xiao-li
• Format: Journal Article
• Language: English
• Published: Changsha Central South University 01.12.2017; Springer Nature B.V
• Subjects: Caverns; Dilatancy; Energy dissipation; Engineering; Failure; Geological hazards; Geotechnical engineering; Karst; Limit analysis; Mathematical analysis; Metallic Materials; Tunnel construction; Water pressure; non-associated flow rule; karst tunnel; upper bound theorem; water inrush; nonlinear failure criterion; safe thickness of rock plug
• ISSN: 2095-2899; 2227-5223
• DOI: 10.1007/s11771-017-3708-1

The geological hazards, such as water inrush and mud outburst, are easily induced by the high water pressure caverns ahead of a karst tunnel face. Therefore, it is a pivotal issue to determine the reserved thickness of rock plug during the construction of tunnels. The limit analysis principle is employed to analyze the safe thickness from the point of energy dissipation, and the nonlinear and non-associated characteristics of geotechnical materials are both considered. On the basis of a plane failure pattern of rock plug, the expressions of detaching curve and rock plug thickness are derived. The effect of each parameter on the safe thickness of rock plug is discussed in detail, which interprets the corresponding failure scope of rock plug. The obtained results indicate that the thickness of rock plug is highly influenced by the nonlinear dilatancy coefficient and the nonlinear coefficient. The proposed method is validated by a comparison of the calculated results with those of the engineering project of the “526 karst cavern” of Yunwushan tunnel. This proposed method can provide reference basis for the design and excavation of karst tunnels in the future.