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Appl. Sci. 2019, 9(8), 1517; https://doi.org/10.3390/app9081517

Physical and Mechanical Characteristics of Soft Rock Tunnel and the Effect of Excavation on Supporting Structure

1
Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China
2
School of Civil Engineering, Changsha University of Science and Technology, Changsha 410076, China
3
Guangxi Communication Investment Group CO., LTD, Nanning 530022, China
4
China 19th Metallurgical Corporation, Chengdu 611730, China
*
Authors to whom correspondence should be addressed.
Received: 1 February 2019 / Revised: 3 April 2019 / Accepted: 8 April 2019 / Published: 12 April 2019
(This article belongs to the Section Environmental and Sustainable Science and Technology)
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Abstract

The problem of large deformation is very prominent in deep-buried tunnel excavation in soft rock, which brings serious potential safety hazards and economic losses to projects. The knowledge of deformation law and support measures is the key to ensure the rational design and safe construction in a large deformation tunnel of soft rock. This paper describes rock physical and mechanical tests and field monitoring is employed to investigate the cause and development process of large deformation in Dongsong hydropower station in Sichuan Province, China. The results show that the free expansion rate of the rock sample is 20.0%, the average expansion stress of the rock sample is 11.0 kPa, and the expansibility of the rock is low. Large deformation of surrounding rock mainly comes from the dilatancy effect with high geostress and relaxation deformation with weak support. Shotcrete sealing exposed surrounding rock, and early strength support avoiding water immersion are useful to deal with the three main factors (weathering, water and confining pressure) that affect the strength of surrounding rocks. The second lining applied in time can effectively limit the further development of stress and deformation of initial support, and prevent the cracking and large deformation of concrete. Clearance convergence is suggested to be the main monitoring work in construction, because of its advantages of intuitive results, easy quality assurance of instrument installation and high accuracy. View Full-Text
Keywords: tunnel construction; large deformation of soft rock; rock physical test; rock mechanics test; deformation law; field monitoring; support optimization tunnel construction; large deformation of soft rock; rock physical test; rock mechanics test; deformation law; field monitoring; support optimization
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Zhu, Y.; Chen, L.; Zhang, H.; Zhou, Z.; Chen, S. Physical and Mechanical Characteristics of Soft Rock Tunnel and the Effect of Excavation on Supporting Structure. Appl. Sci. 2019, 9, 1517.

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