Numerical and experimental analyses of methane leakage in shield tunnel
Jie HE1,2,3, Hehua ZHU1,2,3, Xiangyang WEI1,2,3, Rui JIN1,2,3, Yaji JIAO1,2,3, Mei YIN1,2,3,4()
1. College of Civil Engineering, Tongji University, Shanghai 200092, China 2. State Key Laboratory for Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China 3. Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Tongji University, Shanghai 200092, China 4. Department of Civil and Environmental Engineering, Brunel University, London UB8 3PH, UK
Tunnels constructed in gas-bearing strata are affected by the potential leakage of harmful gases, such as methane gas. Based on the basic principles of computational fluid dynamics, a numerical analysis was performed to simulate the ventilation and diffusion of harmful gases in a shield tunnel, and the effect of ventilation airflow speed on the diffusion of harmful gases was evaluated. As the airflow speed increased from 1.8 to 5.4 m/s, the methane emission was diluted, and the methane accumulation was only observed in the area near the methane leakage channels. The influence of increased ventilation airflow velocity was dominant for the ventilation modes with two and four fans. In addition, laboratory tests on methane leakage through segment joints were performed. The results show that the leakage process can be divided into “rapid leakage” and “slight leakage”, depending on the leakage pressure and the state of joint deformation. Based on the numerical and experimental analysis results, a relationship between the safety level and the joint deformation is established, which can be used as guidelines for maintaining utility tunnels.
The environment is suitable for onsite work and safe for the operation of electrical utilities.
2
0.25%–0.5%
Onsite workers should adopt protective measures, and the operation of electric utilities is still safe.
3
0.5%–1%
Onsite workers should adopt protective measures, but there are risks to the operation of electrical utilities.
4
1%–2%
The methane concentration-monitoring alarm will be triggered.
5
> 2%
There are risks of explosion.
Tab.2
Fig.9
Fig.10
test set
joint opening (mm)
joint dislocation (mm)
test 2
4, 6, 8, 10, 13, 15
0, 10
Tab.3
Fig.11
safety level
methane concentration (v/v)
joint opening
joint dislocation
1
< 0.25%
A ≤ 18 mm
0 mm ≤ S < 8 mm
2
0.25%–0.5%
18 < A ≤ 24 mm
8 mm ≤ S < 12 mm
3
0.5%–1%
24 < A ≤ 30 mm
12 mm ≤ S < 16 mm
4
1%–2%
30 < A ≤ 36 mm
16 mm ≤ S < 24 mm
5
> 2%
A > 36 mm
S ≥ 24 mm
Tab.4
1
F Pearson. How to avoid an explosive situation. Tunnels & Tunnelling International, 1991, 23(9): 27–29
2
R J Proctor. The San Fernando tunnel explosion, California. Engineering Geology, 2002, 67(1–2): 1–3
3
S N VlasovL V MakovskyV E Merkin. Accidents in Transportation and Subway Tunnels: Construction to Operation. Moscow: Elex-KM Publishers, 2001
4
C F C PearsonJ S EdwardsS Durucan. Methane occurrences in the Carsington Aqueduct tunnel project—A case study. In: Proceedings of the Rapid Excavation and Tunneling Conference. Los Angeles: 1989: 11–14
5
W Jaffe, R Lockyer, A Howcroft. The Abbeystead explosion disaster. Annals of Burns and Fire Disasters, 1997, 10(3): 1–4
6
H Copur, M Cinar, G Okten, N Bilgin. A case study on the methane explosion in the excavation chamber of an EPB-TBM and lessons learnt including some recent accidents. Tunnelling and Underground Space Technology, 2012, 27(1): 159–167
7
X B Kang, M Xu, S Luo, Q Xia. Study on formation mechanism of gas tunnel in non-coal strata. Natural Hazards, 2013, 66(2): 291–301 https://doi.org/10.1007/s11069-012-0484-y
8
M Morsali, M Rezaei. Assessment of H2S emission hazards into tunnels: The Nosoud tunnel case study from Iran. Environmental Earth Sciences, 2017, 76(5): 227 https://doi.org/10.1007/s12665-017-6493-0
9
Y Q TangW M YeQ H Zhang. Marsh gas in soft stratum at the estuary of the Yangtze river and safety measures of construction of the tunnel. Journal of Tongji University (Natural Science), 1996, 24(4): 465–470 (in Chinese)
10
Y Q TangB Y LiuS K ZhadY Huang. Research on influence of high-pressure marsh gas on sandy silt engineering. Journal of Tongji University (Natural Science), 2004, 32: 1316–1319 (in Chinese)
11
A Guo, L Shen, J Zhang, J Qin, X Huang, Y Wang. Analysis of influence mode of shallow gas on construction of Hangzhou Metro. Journal of Railway Engineering Society, 2010, 27(9): 78–81
12
A G Guo, L W Kong, L C Shen, J R Zhang, Y Wang, J S Qin, X F Huang. Study of disaster countermeasures of shallow gas in metro construction. Rock and Soil Mechanics, 2013, 34(3): 769–775
13
J K Du. Analysis on the leaking process of toxic gases from chemical accidents and determination of the risky area. China Safety Science Journal, 2002, 12(6): 55–59
14
M Luo Ai, L J Wei. Numerical method of safety distance for poisonous dense gaseous leakage. China Safety Science Journal, 2005, 15(8): 98–100
15
P Li, Y F Ding, P F Weng. Study on leakage and dispersion of dangerous materials in highway tunnel. China Safety Science Journal, 2004, 14(10): 5
16
D D Wang, L Mao, J F Li. On the application of FLUENT to the dispersion of poisonous gases in highway tunnels. Journal of Safety and Environment, 2008, 8(2): 140–143
17
M T Parra, J M Villafruela, F Castro, C Mendez. Numerical and experimental analysis of different ventilation systems in deep mines. Building and Environment, 2006, 41(2): 87–93 https://doi.org/10.1016/j.buildenv.2005.01.002
18
A P Sasmito, E Birgersson, H C Ly, A S Mujumdar. Some approaches to improve ventilation system in underground coal mines environment—A computational fluid dynamic study. Tunnelling and Underground Space Technology, 2013, 34: 82–95 https://doi.org/10.1016/j.tust.2012.09.006
19
F E Camelli, G Byrne, R Löhner. Modeling subway air flow using CFD. Tunnelling and Underground Space Technology, 2014, 43: 20–31 https://doi.org/10.1016/j.tust.2014.02.012
20
A Amouzandeh, M Zeiml, R Lackner. Real-scale CFD simulations of fire in single-and double-track railway tunnels of arched and rectangular shape under different ventilation conditions. Engineering Structures, 2014, 77: 193–206 https://doi.org/10.1016/j.engstruct.2014.05.027
21
N Wei, L Li, C Y Wang. Analysis of harmful gases concentration variation in tunneling ventilation. Journal of China Three Gorges University, 2006, 28(4): 324–327
22
X B Kang, R Ding, M Xu, S J Zhao. Numerical simulation for the ventilation in the construction of high gas tunnel. Journal of Chengdu University of Technology (Science & Technology Edition), 2012, 39(03): 311–316
23
J C Kurnia, A P Sasmito, A S Mujumdar. CFD simulation of methane dispersion and innovative methane management in underground mining faces. Applied Mathematical Modelling, 2014, 38(14): 3467–3484 https://doi.org/10.1016/j.apm.2013.11.067
24
Y Fang, J Fan, B Kenneally, M Mooney. Air flow behavior and gas dispersion in the recirculation ventilation system of a twin-tunnel construction. Tunnelling and Underground Space Technology, 2016, 58: 30–39 https://doi.org/10.1016/j.tust.2016.04.006
25
Y Fang, Z Yao, S Lei. Air flow and gas dispersion in the forced ventilation of a road tunnel during construction. Underground Space, 2019, 4(2): 168–179 https://doi.org/10.1016/j.undsp.2018.07.002
26
C Li, Y Zhao, D Ai, Q Wang, Z Peng, Y Li. Multi-component LBM-LES model of the air and methane flow in tunnels and its validation. Physica A, 2020, 553: 124279 https://doi.org/10.1016/j.physa.2020.124279
27
H N Wu, R Q Huang, W J Sun, S L Shen, Y S Xu, Y B Liu, S J Du. Leaking behavior of shield tunnels under the Huangpu River of Shanghai with induced hazards. Natural Hazards, 2014, 70(2): 1115–1132 https://doi.org/10.1007/s11069-013-0863-z
28
J Wu, Z Liu, S Yuan, J Cai, X Hu. Source term estimation of natural gas leakage in utility tunnel by combining CFD and Bayesian inference method. Journal of Loss Prevention in the Process Industries, 2020, 68: 104328 https://doi.org/10.1016/j.jlp.2020.104328
29
X Ren, C Wu, P Zhou. Gas sealing performance study of rough surface. Journal of Mechanical Engineering, 2010, 46(16): 176–181 https://doi.org/10.3901/JME.2010.16.176
30
N Patir, H S Cheng. An average flow model for determining effects of three-dimensional roughness on partial hydrodynamic lubrication. Journal of Tribology, 1978, 100(1): 12–17
