Abstract
To address post-excavation deformation and failure in deep underground mine tunnels, this study investigates the auxiliary transport tunnel in the northern wing of the 3–1 coal seam at a coal mine in Inner Mongolia. Field structural sampling, laboratory testing, and in situ measurements were conducted to determine the rock mass structure, lithological parameters, and stress distribution in the tunnel roof and floor. A numerical model of the surrounding rock and an analytical model of tunnel floor displacement were developed to analyze the failure mechanism of the tunnel. A support scheme combining pile–foundation unit-type support with anchor bolts and cables is proposed to control tunnel deformation. The effectiveness of this synergistic support scheme was validated through numerical simulation. The research indicates that excavation redistributes the in-situ stress, generating zones of tensile stress and areas of high compressive stress concentration both around the tunnel and deep within the surrounding rock. This leads to the development of both tensile and compressive plastic zones within the surrounding rock, leading to deformation and failure of the rock-tunnel interface. The magnitude of roadway floor displacement is proportional to both the width of the plastic zones at the floor ends and the stress concentration factors on each side. The point of maximum floor displacement shifts toward the side with the wider plastic zone or the higher stress concentration factor. Under the combined support system, the maximum displacements of the roof and floor were reduced by 93% and 82%, respectively, while the maximum deformation values for the roadway sides decrease by 78% and 93%, respectively. The displacement patterns of the roof and floor were significantly improved, with the plastic strain zone in the surrounding rock completely severed and the maximum plastic strain value reduced by approximately 80%. Therefore, effective control of tunnel deformation relies on enhancing the integrity of the surrounding rock and reducing both stress concentration and plastic flow. The synergistic effect of the pile-foundation unit support with the anchor bolts and cables effectively mitigated post-excavation deformations, including floor heave, roof settlement, and sidewall convergence, demonstrating the effectiveness and feasibility of the proposed synergistic support scheme for mitigating tunnel deformation.
Data availability
All data generated or analysed during this study are included in this published article.
References
Lihui, S. et al. Experimental research on mechanism and controlling of floor heave in deep soft rock roadway. J. Min. Saf. Eng. 34(02), 235–242 (2017).
Ziwei, D. et al. Asymmetric failure mechanism and control of entries inshort-distance coal seam. J. Min. Saf. Eng. 41(02), 242–254 (2024).
Li, J. et al. Evolution of the roof caving and fracture zones during mining of close range coal seams. Sci. Rep. 15(1), 31221 (2025).
Fei, L. et al. Failure analysis and prediction of roof instability in end face under repeated mining using early warning system. Sci. Rep. 13(1), 8764 (2023).
Yaodong, J. & Shiliang, L. Research on the mechanism of bottom bulging in roadways. J. China Coal Sci. 04, 343–351 (1994).
Xu, Q. et al. Mechanism and control of floor heave in two entry retained roadways using dense boreholes. Sci. Rep. 15(1), 17243 (2025).
Xue, B. et al. Research on bending-slip rib spalling and rib stability of extra-thick hard coal wall. Sci. Rep. 15(1), 26796 (2025).
Zhao, J. et al. Study on instability mechanisms and control of coal pillar spalling and coal crumbs leakage during working face crossing faults. Sci. Rep. 14(1), 26667 (2024).
Hongpu, K. & Shiliang, L. Analysis of the mechanism of roadway floor bulging. China J. Rock Mech. Eng. 04, 362–373 (1991).
Hongpu, K. The mechanism and prevention of floor bulging in soft rock roadways. M. Beijing: Coal Industry Publishing House, 1–3 (1993).
Yongxue, X., Lijun, K. & Qingxin, Q. Coal cutting height affected to stability of coal wall in fully mechanized top coal cavingmining face with high coal cutting height. J. Coal Sci. Technol. 36(12), 1–3 (2008).
Yajun, L. Prevention technology of coal-wall slide and roof fall in large-mining height mining face. J. Coal Min. Technol. 19(04), 106–107 (2014).
Hongbao, Z. et al. Study of the mechanism and evolution law of unsymmetricalfailure of the mining roadway in close distance coal seam. J. China Univ. Min. Technol. 50(06), 1029–1040 (2021).
Zhuoyue, D. et al. Mechanism and prevention of bottom heave in large cross-sectionInclined shaft roadways in swelling soft rocks. J. Sci. Technol. Eng. 25(11), 4489–4495 (2025).
Xuegui, S. et al. Stability control of the roadway groupunder the influence of overlying goaf. J. Min. Saf. Eng. 33(03), 415–422 (2016).
Yimin, S. et al. Simulation test and numerical analysis of the performance of hydraulic support for pile foundation. J Coal Sci. Technol. 53(11), 1–11 (2025).
Xiong, Y. et al. Instability control of roadway surrounding rock in close-distance coal seam groups under repeated mining. Energies 14(16), 5193 (2021).
Fengfeng, W. et al. Control technology and application of variable-diameter zoned pressure relief forsurrounding rock in deep soft rock and large deformation roadway. J. Coal Sci. Technol. 53(02), 53–67 (2025).
Zhengian, M. et al. Floor roadway stabiltyin repeated mining of closedistance coal seams in luling coal mine. Chin. J. Rock Mech. Eng. 34(S1), 3320–3327 (2015).
Yu, G. et al. Study on deformation failure and control of surrounding rock insoft rock roadway in close range coal seam with overhead mining. J Min. Saf. Eng. 35(06), 1142–1149 (2018).
Guo, H. Research and application of anti-impact characteristics of unit type roadway hydraulic support. D. Liaoning Tech Univ. (2024).
Yimin, S., XIaodong J., Hailiang X., et al. Multi-row telescopic pile foundation three-hinged arch support structure, CN119466891A [P/OL].
Funding
National Major Scientific Instruments and Equipments Development Project of National Natural Science Foundation of China: 52427805.
Author information
Authors and Affiliations
Contributions
L.Y. Gou for writing the article, D. An and Y.M. Song for conceptualization, H.L. Xu and W.J. Xiao for methodology, X.D. Jiang for validation, L.Y. Gou for graphic editing, and D. An for visualization and review, the authors have read and agree with the published paper. All authors have read and agreed to the published version of the manuscript.
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
About this article
Cite this article
Gou, L., An, D., Song, Y. et al. Research on deformation mechanisms in deep excavation tunnels and the application of the pile foundation-unit-type support. Sci Rep (2026). https://doi.org/10.1038/s41598-026-43056-z
Received:
Accepted:
Published:
DOI: https://doi.org/10.1038/s41598-026-43056-z
