Key Takeaways & Executive Findings
- •• Wedge block geometry significantly influences the mechanical behavior and failure modes of arched tunnel roofs under biaxial loading. • Support measures are more effective in enhancing the strength of stable wedge blocks (T3, T4) compared to unstable ones (T1, T2). • Failure modes are classified as rock-dominated, wedge-dominated, or co-dominated, with cracks initiating near the wedge and propagating outward. • Unsupported conditions lead to high stress differences and localized shear failure, while support alters crack distribution and stress redistribution.
Abstract
The stability of underground tunnel roofs is strongly influenced by wedge blocks formed by complex joint networks. The mechanical behavior and failure mechanisms of different roof wedge blocks in arched holes were investigated under biaxial stress conditions. The crack evolution and failure modes of the specimens were analyzed through acoustic emission (AE), digital image correlation (DIC), and discrete element method (DEM). Results show significant variations in mechanical properties: specimens T1 (extremely unstable triangular) and T2 (extremely unstable quadrilateral) exhibited higher strength than T3 (extremely stable triangular) and T4 (extremely stable quadrilateral), while support more effectively enhanced the strength of T3 and T4. Failure modes were classified as rock-dominated, wedge-dominated, or co-dominated. Cracks typically initiated near the wedge and propagated outward. Unsupported specimens developed tensile cracks at the hole bottom, shear cracks at the sides, and mixed cracks along wedge boundaries, whereas supported specimens mainly exhibited cracks at the roof and sides. Stress analysis indicated that unsupported conditions induced high stress differences, promoting localized shear failure. Wedge geometry significantly affected shear stress redistribution at the roof. These findings highlight the critical role of support and wedge block geometry in controlling stress distribution and failure mechanisms in arched tunnels.
1. Introduction
Tunnel roof stability is one of the key issues in underground safety. Roof failure is a common disaster in underground arch structure tunnels and chambers [1,2]. It is common for excavations to cut through intersecting discontinuities in the natural rock to form wedge blocks that fall from the roof, such as the examples shown in Fig. 1. The presence of roof blocks, especially wedge blocks, significantly alters the stress distribution and mechanical response of the rocks surrounding the excavation, and therefore is one of the most important factors impacting the stability of the structure [3,4]. Therefore, studying the mechanical behaviors and failure mechanisms of arched structures containing different types of roof wedge blocks is of great significance for the design and construction of underground excavations.
In the current study, tunnel roof failure is affected by a variety of factors such as the physical properties of the surrounding rock, joint characteristics, and support measures [6,7]. Qin et al. [8] revealed the collapse patterns of layered roof strata and the detachment laws of additional blocks, and proposed a progressive curve destruction mechanism. Yang et al. [9] revealed the evolution law of stress-displacement-damage of the surrounding rock in the oblique ''upper soft and lower hard'' layer, and analysed the asymmetric failure mode of block fall and hard rock contraction and deformation in the soft rock area of the roof. Hatzor et al. [10] revealed the structural characteristics of anisotropic rocks due to slender prismatic key blocks and analysed the effect of joint orientation on the roof loosening zone. In the study of blocky rock masses, Zhang et al. [11,12] proposed a reliable support design method based on three-dimensional block cutting analysis, which provides a quantitative solution for progressive failure prevention and control of blocky rock mass. Wang et al. [13] proposed an extended key block theory based on 3DEC and established multiple block failure modes. In terms of block rock control, Lin et al. [3] analysed the three-dimensional stability of key blocks in underground excavations.
Loading authentic research manuscript (Pages 1–5)...
Ruiyang Bi, Chaoshui Xu, Minghui Liu, Kun Du (2025). Failure mechanisms and mechanical behavior of wedge-containing tunnel roof rock mass under biaxial loading. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2025.06.002
Research & Educational Purpose Only:The translations, structured abstracts, analytical annotations, and data reports provided by SinoTechIntel are intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoTechIntel claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What are the main failure modes of wedge-containing tunnel roofs under biaxial loading?
The failure modes are classified as rock-dominated, wedge-dominated, or co-dominated, depending on the wedge geometry and support conditions.
How does support affect the mechanical behavior of wedge-containing tunnel roofs?
Support enhances the strength of stable wedge blocks (T3, T4) more effectively than unstable ones (T1, T2), and alters crack distribution, reducing stress concentration and localized shear failure.
What methods were used to analyze crack evolution and failure modes?
Acoustic emission (AE), digital image correlation (DIC), and discrete element method (DEM) were used to analyze crack evolution and failure modes.
What is the significance of wedge geometry in tunnel roof stability?
Wedge geometry significantly affects shear stress redistribution at the roof, influencing the initiation and propagation of cracks and the overall stability of the tunnel.
Where do cracks typically initiate in unsupported specimens?
In unsupported specimens, tensile cracks initiate at the hole bottom, shear cracks at the sides, and mixed cracks along wedge boundaries.
Related Technical Papers & Translations
A Novel Approach for Enhanced Brain Tumor Segmentation Using Multimodal MRI and Deep Learning
Brain tumor segmentation from multimodal MRI is crucial for diagnosis and treatment planning. In this study, we propose a novel deep learning framework that integrates structural and functional imaging modalities to improve segmentation accuracy. Our method employs a multi-scale attention mechanism and a hybrid loss function to handle class imbalance and boundary ambiguity. Evaluated on the BraTS benchmark, our approach achieves state-of-the-art performance, with Dice scores of 0.91, 0.87, and 0.84 for whole tumor, core, and enhancing tumor, respectively. Furthermore, we demonstrate the generalizability of our model across different scanners and protocols. Our findings suggest that the proposed method can significantly aid clinical decision-making and surgical planning.
Investigation of coupled acoustic and electrical responses and early warning approaches during re-loading of damaged coal
Initial damage from engineering disturbances in deep coal mining degrades mechanical properties and heightens dynamic-hazard risks, challenging conventional monitoring. This study probes the coupled acoustic-electrical responses of initially damaged coal under reloading and develops a multi-parameter, multi-level dynamic integrated early-warning model. Using a true-triaxial Split Hopkinson Pressure Bar (SHPB) system, we prepared specimens with graded damage by varying static deviatoric stresses and dynamic impacts. Uniaxial compression reloading was conducted with synchronous acoustic emission (AE) and resistivity monitoring. Joint time-domain responses of force, acoustics, and electricity delineated distinct loading stages. Time-frequency features were extracted via Fourier and wavelet transforms; crack architecture was quantified by 3D AE localization and fractal-dimension analysis. Initial damage markedly reduced load-bearing capacity. Resistivity decreased sharply with increasing deviatoric stress, while cumulative AE counts increased strongly. The AE spectrum evolved from bimodal to broadband with low- and high-frequency enhancement. The resistivity spectrum showed progressive bandwidth broadening, energy amplification, and high-frequency advancement. The AE spatial fractal dimension rose significantly during compaction. An integrated warning system combining multiscale entropy fusion, Temporal Convolutional Network (TCN)-Transformer forecasting, recurrence-network analysis, and a Bayesian framework yielded a 28.4 s lead time, offering a theoretical basis and technical pathway for intelligent prevention of dynamic hazards.
Influence of aggregate particle size on fracture behavior and energy evolution of cemented rockfill in the post-peak stage
Cemented rockfill (CRF) combines structural support with sustainable reuse of coal-derived solid waste. This study integrates digital image correlation, acoustic emission monitoring, and finite–discrete element simulations to investigate mechanical behavior, fracture development, and energy evolution of CRF containing 54% aggregate content with three grain-size distributions (5–10, 10–20, and 20–30 mm). Results indicate finer aggregates raise compressive strength and elastic modulus, and increase post-peak softening and residual stiffness. Fracture patterns transition from dominantly unidirectional failure in coarse specimens to pronounced X-shaped conjugate shear in fine specimens, with cracks initiating at boundaries and propagating inward. The proportion of failed joints at comparable strains decreases markedly with finer gradation, reflecting a more homogeneous crack network that enhances post-peak load retention and produces frequent minor stress fluctuations. Energy analyses reveal a coarse > medium > fine ordering in cumulative dissipation; however, finer aggregates delay rapid kinetic and dissipative energy release, promoting slower energy redistribution and improved load resistance. These findings quantify how aggregate gradation controls deformational mechanisms, crack topology, and energy partitioning, and provide design guidance for optimizing aggregate size and cementitious composition to enhance ductility, energy absorption, and structural reliability of CRF in underground engineering.