Conversion of tunnel excavation methods and optimization of support measures under transformation of rock stratum: A case study

Abstract

Layered rock masses represent complex geological formations characterized by pronounced anisotropy in strength. This study monitors stress/deformation during construction to summarize layered rock mass deformation and support stress characteristics based on Yunwushan Tunnel. Shale shows greater vault settlement and asymmetric support deformation than sandstone. The excavation was optimized by establishing a numerical model, analyzing the advanced support effect, and redesigning the anchor rod to control the asymmetric large deformation. The results show that: 1) It is effective to set a transition section before the sudden change of rock mass, and the optimal distance for setting the transition section is 6 m. 2) The implementation of advance small pipe support has been shown to effectively mitigate settlement in the tunnel arch, whereas anchor bolt support is effective in controlling the horizontal convergence of the surrounding rock. 3) Adjusting the angle of the anchor bolt is a cost-effective reinforcement method when facing asymmetric deformation. 4) It is recommended to flexibly adjust the angle of the anchor bolts and increase the advance small pipe support in mountain tunnel projects under the transformation of rock strata. These outcomes may serve as a valuable reference for the design and construction of similar engineering projects.

Keywords

ubiquitous-joint model / layered surrounding rock / large deformation / asymmetric support / numerical simulation

References

[1] Adhikary D P, Guo H. An orthotropic cosserat elastoplastic model for layered rocks [J]. Rock Mechanics and Rock Engineering, 2002, 35(3): 161-170.

[2] Dubey R K, Gairola V K. Influence of structural anisotropy on creep of rocksalt from Simla Himalaya, India: An experimental approach [J]. Journal of Structural Geology, 2008, 30(6): 710-718.

[3] Wang P-t, Cai M-f, Ren F-H. Anisotropy and directionality of tensile behaviours of a jointed rock mass subjected to numerical Brazilian tests [J]. Tunnelling and Underground Space Technology, 2018, 73: 139-153.

[4] Liu X-z, Liu F, Song K-Z. Mechanism analysis of tunnel collapse in a soft-hard interbedded surrounding rock mass: A case study of the Yangshan Tunnel in China [J]. Engineering Failure Analysis, 2022, 138: 106304.

[5] Lu S, Sun Z-y, Zhang D-l, et al.. Numerical modelling and field observations on the failure mechanisms of deep tunnels in layered surrounding rock [J]. Engineering Failure Analysis, 2023, 153: 107598.

[6] Shen F-x, Song Y-q, Zhao W-c, et al.. Experimental study on deformation failure mechanism of surrounding rocks for the deep-buried twin tunnels in inclined layered strata during the excavation [J]. Rock Mechanics and Rock Engineering, 2023, 56(3): 2311-2331.

[7] Labiouse V, Vietor T. Laboratory and in situ simulation tests of the excavation damaged zone around galleries in opalinus clay [J]. Rock Mechanics and Rock Engineering, 2014, 47(1): 57-70.

[8] Moussaei N, Sharifzadeh M, Sahriar K, et al.. A new classification of failure mechanisms at tunnels in stratified rock masses through physical and numerical modeling [J]. Tunnelling and Underground Space Technology, 2019, 91: 103017.

[9] Shabanimashcool M, Li C C. Analytical approaches for studying the stability of laminated roof strata [J]. International Journal of Rock Mechanics and Mining Sciences, 2015, 79: 99-108.

[10] He L, Zhang Q B. Numerical investigation of arching mechanism to underground excavation in jointed rock mass [J]. Tunnelling and Underground Space Technology, 2015, 50: 54-67.

[11] Sainsbury B L, Sainsbury D P. Practical use of the ubiquitous-joint constitutive model for the simulation of anisotropic rock masses [J]. Rock Mechanics and Rock Engineering, 2017, 50(6): 1507-1528.

[12] Tian Y, Shu X-y, Tian H-m, et al.. Effect of horizontal stress on the mesoscopic deformation and failure mechanism of layered surrounding rock masses in tunnels [J]. Engineering Failure Analysis, 2023, 148: 107226.

[13] Xia B-w, Hu K, Lu Y-y, et al.. Model test study on influences of layered rock mass dip angle on stability of deep-buried tunnel [J]. Applied Mechanics and Materials, 2011, 90–93: 2363-2371.

[14] Li A, Liu Y, Dai F, et al.. Continuum analysis of the structurally controlled displacements for large-scale underground Caverns in bedded rock masses [J]. Tunnelling and Underground Space Technology, 2020, 97: 103288.

[15] Luo P-k, Wang L-c, Li D-y, et al.. Deformation and failure mechanism of horizontal soft and hard interlayered rock under uniaxial compression based on digital image correlation method [J]. Engineering Failure Analysis, 2022, 142: 106823.

[16] Wang F N, Guo Z B, Qiao X B, et al.. Large deformation mechanism of thin-layered carbonaceous slate and energy coupling support technology of NPR anchor cable in Minxian Tunnel: A case study [J]. Tunnelling and Underground Space Technology, 2021, 117: 104151.

[17] Cao C-y, Shi C-h, Lei M-f, et al.. Squeezing failure of tunnels: A case study [J]. Tunnelling and Underground Space Technology, 2018, 77: 188-203.

[18] Hu X-y, Gutierrez M. Viscoelastic Burger’s model for tunnels supported with tangentially yielding liner [J]. Journal of Rock Mechanics and Geotechnical Engineering, 2023, 15(4): 826-837.

[19] Aygar E B. Performance of the flexible and rigid lining under earthquake impact and weakness of the new Austrian tunneling method (NATM) principles, a specific case study of the Bolu tunnel [J]. Sustainability, 2023, 15(21): 15544.

[20] Hasanpour R, Chakeri H, Ozcelik Y, et al.. Evaluation of surface settlements in the Istanbul metro in terms of analytical, numerical and direct measurements [J]. Bulletin of Engineering Geology and the Environment, 2012, 71(3): 499-510.

[21] Elyasi A, Moradi T, Moharrami J, et al.. Efficiency assessment of L-profiles and pipe fore-poling pre-support systems in difficult geological conditions: A case study [J]. Structural Engineering and Mechanics, 2016, 57(6): 1125-1142.

[22] Chen S L, Tsai Y H, Zhang X-l, et al.. Numerical analysis of the vertical crown displacements in triple adjacent tunnels with rock bolts and pipe roofings [J]. Processes, 2022, 10(10): 2062.

[23] Fan X, Yang Z-j, Li K-hui. Effects of the lining structure on mechanical and fracturing behaviors of four-arc shaped tunnels in a jointed rock mass under uniaxial compression [J]. Theoretical and Applied Fracture Mechanics, 2021, 112: 102887.

[24] Tan Z-s, Li S-t, Yang Y, et al.. Large deformation characteristics and controlling measures of steeply inclined and layered soft rock of tunnels in plate suture zones [J]. Engineering Failure Analysis, 2022, 131: 105831.

[25] Zhou Y-y, Feng X-t, Xu D-p, et al.. An enhanced equivalent continuum model for layered rock mass incorporating bedding structure and stress dependence [J]. International Journal of Rock Mechanics and Mining Sciences, 2017, 97: 75-98.

[26] Zhou Y-y, Xu D-p, Liu K, et al.. Understanding the failure mechanism of a large underground cavern in steeply dipping layered rock mass using an enhanced ubiquitous-joint model [J]. Bulletin of Engineering Geology and the Environment, 2021, 80(6): 4621-4638.

[27] Zhou P-f, Shen Y-s, Zhao J-f, et al.. Research on disaster-induced mechanism of tunnels with steeply dipping phyllite strata based on an improved ubiquitous-joint constitutive model [J]. Chinese Journal of Rock Mechanics and Engineering, 2019, 38(9): 1870-1883. (in Chinese).

RIGHTS & PERMISSIONS

Central South University