Biaxial compression behavior and stability analysis of wedge blocks in tunnel sidewalls: Experimental investigation and support effect evaluation

Abstract

In complex jointed rock masses, wedge blocks are likely to form on the tunnel sidewalls after excavation, and the mechanical properties and stress environment of the surrounding rock have a significant impact on their stability. In this study, cubic rock specimens with prefabricated wedge blocks and arched tunnel features were tested under biaxial compression. Acoustic emission (AE) and digital image correlation technologies were used to monitor crack propagation and specimen failure in real-time. The results showed that supported specimens exhibited higher strength during both the peak and post-peak stages, with a slower strength decline after the peak. The support regulated AE hit rates and enhanced energy storage capacity. Different specimens displayed varying strain evolution, with supported specimens generally having higher lateral strain than shear strain. In unsupported specimens, tensile and shear stresses were concentrated at the wedge block apex, while supported specimens showed more complex stress variations, especially under the influence of wedge blocks. Stable specimens experienced shear sliding failure, while extremely stable specimens experienced both shear sliding and tensile fracture. As horizontal stress (σ₃) increased, specimen strength and wedge block failure both increased. Triangular wedge blocks played a decisive role in tunnel stability, with extremely stable triangular blocks providing greater safety. In addition, a typical stability analysis method for wedge blocks was proposed. The findings provide a scientific basis for rock mass stability assessment and support measure selection in tunnel design.

Keywords

Underground mining / Wedge blocks / Biaxial compression / Discrete element simulation / Tunnel stability

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

CRediT authorship contribution statement

Ruiyang Bi: Formal analysis, Writing - original draft, Conceptualization. Minghui Liu: Validation, Investigation. Jian Zhou: Investigation. Kun Du: Conceptualization, Funding acquisition, Resources.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

The authors would like to thank the National Natural Science Foundation of China (Grant No. 52374150), the Key Science and Technology Program of the Ministry of Emergency Management of the People's Republic of China (2024EMST141405), and the Innovation-Driven Project of Central South University (No. 2023ZZTS0714).

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