Numerical analysis and field monitoring tests on shallow tunnels under weak surrounding rock

Abstract

The Jianpudong No. 4 tunnel is a shallow tunnel, which belongs to Shaoshan County scenic highway in Hunan province, China and whose surrounding rock is weak. According to its characteristics, the field monitoring tests and numerical analysis were done. The mechanical characteristics of shallow tunnels under weak surrounding rock and the stress—strain rule of surrounding rock and support were analyzed. The numerical analysis results show that the settlement caused by upper bench excavating accounts for 44% of the total settlement, and the settlement caused by tunnel upper bench supporting accounts for 56% of the total settlement. The maximum axial force of shotcrete lining is 177.2 kN, which locates in hance under the secondary lining. The maximum moment of shotcrete lining is 5.08 kN·m, which locates in the arch foot. The stress curve of steel arch has three obvious stages during the tunnel construction. The maximum axial force of steel arch is 297.4 kN, which locates in tunnel vault. The axial forces of steel arch are respectively 23.5 kN and −21.8 kN, which is influenced by eccentric compression of shallow tunnel and locates in hance. The results show that there is larger earth pressure in tunnel vault which is most unfavorable position of steel arch. Therefore, the advance support should be strengthened in tunnel vault during construction process.

Keywords

tunnel engineering / shallow tunnel / weak surrounding rock / numerical analysis / field monitoring tests

References

[1] QinC-b, SunZ-b, LiangQ. Limit analysis of roof collapse in tunnels under seepage forces condition with three-dimensional failure mechanism [J]. Journal of Central South University, 2013, 20(8): 2314-2322

[2] ZhouB, XieX-y, YangY-b, JiangJ-c. A novel vibration-based structure health monitoring approach for the shallow buried tunnel [J]. Computer Modeling in Engineering & Sciences, 2012, 86(4): 321-348

[3] MollonG, DiasD, SoubraA H. Rotational failure mechanisms for the face stability analysis of tunnels driven by a pressurized shield [J]. International Journal for Numerical and Analytical Methods in Geomechanics, 2011, 35(12): 1363-1388

[4] LaiH-p, XuX-s, ChanuR-c, XieY-l. Study on mechanical characteristics of highway tunnel expansion [J]. China Journal of Highway and Transport, 2014, 27(1): 84-93

[5] KontogianniV, StirosS. Convergence in weak rock tunnels [J]. Tunnels and Tunneling International, 2006, 38(2): 36-39

[6] PopovN A, KrasyukA M, LuginI V, PavlovS A, ZedgenizovD V. Improvement of shallow subway tunnel ventilation procedures [J]. Journal of Mining Science, 2015, 50(5): 943-952

[7] OresteP P, DiasD. Stabilisation of the excavation face in shallow tunnels using fibreglass dowels [J]. Rock Mechanics and Rock Engineering, 2012, 45(4): 499-517

[8] YangJ-s, ZhangJ, YangF. Stability analysis of shallow tunnel face using two-dimensional finite element upper bound solution with mesh adaptation [J]. Yantu Lixue/Rock and Soil Mechanics, 2015, 36(1): 257-264

[9] DuanB-f, ZhuY-l, WuS-z. Monitoring and controlling technology for blasting vibration induced by a shallowburied tunnel in a complex environment [J]. Modern Tunnelling Technology, 2013, 50(3): 142-146

[10] KunM, OnarganT. Influence of the fault zone in shallow tunneling: A case study of izmir metro tunnel [J]. Tunnelling and Underground Space Technology, 2013, 33: 34-45

[11] ZhouZ-q, LiS-c, LiL-p, SuiB, ShiS-s, ZhangQ-q. Causes of geological hazards and risk control of collapse in shallow tunnels [J]. Yantu Lixue/Rock and Soil Mechanics, 2013, 34(5): 1375-1382

[12] PopovN A, KrasyukA M, LuginI V, PavlovS A, ZedgenizovD V. Improvement of shallow subway tunnel ventilation procedures [J]. Journal of Mining Science, 2015, 50(5): 943-952

[13] IbrahimO. A new approach for estimating the transverse surface settlement curve for twin tunnels in shallow and soft soils [J]. Environmental Earth Sciences, 2014, 72(7): 2357-2367

[14] SeoD H, LeeT H, KimD R, ShinJ H. Pre-nailing support for shallow soft-ground tunneling [J]. Tunnelling and Underground Space Technology, 2014, 42: 216-226

[15] IbrahimO. Interaction of longitudinal surface settlements for twin tunnels in shallow and soft soils: The case of istanbul metro [J]. Environmental Earth Sciences, 2013, 69(5): 1673-1683

[16] FraldiM, GuarracinoF. Evaluation of impending collapse in circular tunnels by analytical and numerical approaches [J]. Tunnelling and Underground Space Technology, 2011, 26(4): 507-516

[17] ZhaoY, PengH-y, LuY-y. Study on nonlinear dynamic character of interaction between surrounding rock and support structure of deep buried tunnel [J]. Journal of Highway and Transportation Research and Development, 2009, 26(11): 98-102

[18] JTJ D70-2004. Code for design of road tunnel [S]. 2004. (in Chinese)