On-Site Monitoring for the Stability Evaluation of a Highway Tunnel above Goaves of Multi-Layer Coal Seams

Guangtao Cai,Jilin Wang,Wanghua Sui,Shenglin Wu,Jiaxing Chen

doi:10.3390/app11167383

Abstract

This paper presents the on-site monitoring of a medium–long highway tunnel constructed above a goaf of a multi-layer coal seam, in order to evaluate and maintain safety during operation. The case study of the Tianzimiao medium–long highway tunnel in Shanxi province was conducted above a goaf of a multi-layer coal seam with typical geological and engineering conditions in China, where a total of four coal seams (seam no. 3, 8, 12, and 15) were mined out with a total thickness of up to 11 m. Methods including data collection, engineering geological survey, drilling, geophysical prospecting, testing, and on-site monitoring were adopted, and a geo-mechanical model was established to conduct the research. Stratified monitoring was applied to investigate the individual settlement and deformation of the four layers of the goaf below, and a prediction of the possible deformation in tunnel floor ground was made based on the stratified measurements. The settlement of the tunnel sidewall, the internal stress in the fractured zone of the surrounding rock, and the deformation above the tunnel entrance were also monitored, and the monitoring data were compared with the numerical simulation results for the safety evaluation of the tunnel. The results show that the current tunnel deformation values and trend are both within the safety scope of the evaluation and prediction. The stability evaluation method for the multi-layer goaf used in this paper and the long-term on-site monitoring and timely feedback during operation is helpful to ensure the safe use of the tunnels above the goaves of multi-layer thick coal seams.

Highlights

Geological disasters such as ground subsidence caused by coal mining have become increasingly prominent in China
With the rapid construction of highways and urban highway networks in China, there has been an increasing amount of highway construction running through coal mining subsidence areas; for example, part of the expressways in Guangdong province [2], and the construction of the Outer Ring Expressway of Xuzhou, Jiangsu province [2,3], encountered geotechnical engineering problems due to passing through the goaf of coal mines
Huang [12] conducted research on the surrounding rock stress of a tunnel by on-site monitoring and the numerical simulation method, presenting that the secondary lining receives the contact pressure created by rheological rock

Summary

Introduction

Geological disasters such as ground subsidence caused by coal mining have become increasingly prominent in China. 6000 km of land suffered geological disasters caused by the subsidence of mined-out areas [1]. With the rapid construction of highways and urban highway networks in China, there has been an increasing amount of highway construction running through coal mining subsidence areas; for example, part of the expressways in Guangdong province [2], and the construction of the Outer Ring Expressway of Xuzhou, Jiangsu province [2,3], encountered geotechnical engineering problems due to passing through the goaf of coal mines. Huang [12] conducted research on the surrounding rock stress of a tunnel by on-site monitoring and the numerical simulation method, presenting that the secondary lining receives the contact pressure created by rheological rock.

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Results

Conclusion