Work

Mechanism of Separation and Fracturing of Vault Strata in Underground Cavities in Gentle-Dipping Bedded Rock Masses

Year: 2026

Type: article

Abstract: To accurately reveal the mechanism of interlayer separation, crack propagation, and progressive instability of vault strata in underground cavities in gentle-dipping bedded rock masses, this paper systematically elucidates the entire mechanical behavior of separation evolution, crack penetration, structural transformation, and step-by-step caving of vault bedded rock masses under excavation disturbance through a comprehensive integration of excavation unloading mechanical analysis, the Griffith strength criterion, and the dynamic transformation theory of beam structures. The results show that excavation induces radial unloading and circumferential stress concentration in the surrounding rock, and the vault rock mass preferentially undergoes interlayer separation along near-horizontal gentle-dipping bedding planes, forming a spatial zoning feature of gradient attenuation from bottom to top: a strong separation zone at the lower part, a transition zone in the middle, and a closed zone at the upper part. The vault strata undergo a cyclic dynamic structural transformation of cantilever beam–fixed-end beam–simply supported beam, exhibiting stepped fracturing and layer-by-layer caving failure characteristics. The fracture and caving range follow a three-stage evolution law of initial increase–peak–subsequent convergence and stabilization. Based on the elastic mechanics stress transformation relationship, a Griffith initiation criterion for surrounding rock of circular cavities under non-axisymmetric loads is derived and established, and mechanical calculation models of single beam and composite beam suitable for stratified rock masses are constructed, which quantitatively reveal the controlling effects of tensile strength of strata, lateral pressure coefficient, tunnel diameter, stratification thickness, and burial depth on crack initiation and failure degree. Verified by a city-gate-shaped tunnel numerical test and an practical engineering case of a large-scale underground tunnel in western China, the theoretical calculation results are in good agreement with the on-site failure morphology and numerical analysis results. The established separation criterion and mechanical model can effectively predict the initiation risk and stability critical conditions of vault strata. The research results can provide a theoretical basis and technical support for the stability evaluation, early warning, and optimal design of support structures of surrounding rock in underground engineering in gentle-dipping bedded rock masses.

Source: Applied Sciences

DOI: 10.3390/app16157517

Authors: Guofeng Li, Ning Li, Yue Bai, Kaiqiang Wu, Yanbo Hu

Institution: Xi'an University of Technology

Language: English

Topic: Geomechanics and Mining Engineering

Subfield: Mechanics of Materials

Field: Engineering

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $2,896

Funder: National Natural Science Foundation of China