Frontiers of Structural and Civil Engineering
>> 2019,
Volume 13,
Issue 6
doi:
10.1007/s11709-019-0563-1
RESEARCH ARTICLE
Quantitatively assessing the pre-grouting effect on the stability of tunnels excavated in fault zones with discontinuity layout optimization: A case study
. State Key Laboratory for Geo-mechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou 221116, China.. School of Civil and Transportation Engineering, Hebei University of Technology, Tianjin 300401, China.. Geotechnical & Structural Engineering Research Center, Shandong University, Jinan 250061, China
Accepted: 2019-10-22
Available online: 2019-10-22
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Abstract
Pre-grouting is a popular ground treatment strategy utilized to enhance the strength and stability of strata during the excavation of a tunnel through a fault zone. Two important questions need to be answered during such an excavation. First, how should the grouting size be determined? Second, when should excavation begin after grouting? These two questions are conventionally addressed through empirical experience and standard criteria because a reliable quantitative approach, which would be preferable, has not yet been developed. To address these questions, we apply a recently proposed numerical approach known as discontinuity layout optimization, an efficient node-based upper bound limit analysis method. A case study is provided utilizing a tunnel located in a stratum characterized by complicated geological conditions, including soft soil and a fault zone. The factor of safety is used to quantitatively assess the stability of the tunnel section. The influences of the grouted zone thickness and the time-dependent material properties of the grouted zone on the stability of the tunnel section are evaluated, thereby assisting designers by quantitatively assessing the effects of pre-grouting.
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