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Model Test Study on Influence of Excavation Methods on Stability of Surrounding Rocks of the Soft Rock Tunnel in High Geostress Field
（1 Institute of Transportation Development Strategy & Planning of Sichuan Province, Chengdu 610041; 2 School of Civil Engineering,Southwest Jiaotong University, Chengdu 610031; 3 Key Laboratory of Ministry of Education of Transportation Tunnel Engineering,Southwest Jiaotong University, Chengdu 610031)
Abstract Different excavation methods often have different influences on the stabilities of the surrounding rocks. Based on the Lanjiayan highway tunnel project, a three-dimensional geomechanical model test is conducted, the influences of three-bench method, upper-bench and lower-bench method as well as upper-bench and lower-bench method with reserved core soil on the stabilities of soft rock tunnels in high in-situ stress field are studied. The research results show that: (1) the crown settlement and arch foot convergence experience three development stages, i.e.advance deformation, excavation deformation and convergence in sequence with the variation of excavation step under above mentioned three construction methods, with an ascending order of three-bench method, upper-bench and lower-bench method with reserved core soil method and upper-bench and lower-bench method in term of deformation magnitude; (2) the radial force between primary support and surrounding rock is pressure with similar distribution characteristics, the maximum and minimum surrounding rock pressures occur at the foot of sidewall and invert crown, with an ascending order of three-bench method, upper-bench and lower-bench method with reserved core soil and upper-bench and lower-bench method in term of pressure magnitude; (3) the three-bench method is the one that is most conducive to the stability of surrounding rock during the construction of soft rock tunnel in high geostress field and meeting the requirements of construction progress to a certain extent.
Abstract：
Different excavation methods often have different influences on the stabilities of the surrounding rocks. Based on the Lanjiayan highway tunnel project, a three-dimensional geomechanical model test is conducted, the influences of three-bench method, upper-bench and lower-bench method as well as upper-bench and lower-bench method with reserved core soil on the stabilities of soft rock tunnels in high in-situ stress field are studied. The research results show that: (1) the crown settlement and arch foot convergence experience three development stages, i.e.advance deformation, excavation deformation and convergence in sequence with the variation of excavation step under above mentioned three construction methods, with an ascending order of three-bench method, upper-bench and lower-bench method with reserved core soil method and upper-bench and lower-bench method in term of deformation magnitude; (2) the radial force between primary support and surrounding rock is pressure with similar distribution characteristics, the maximum and minimum surrounding rock pressures occur at the foot of sidewall and invert crown, with an ascending order of three-bench method, upper-bench and lower-bench method with reserved core soil and upper-bench and lower-bench method in term of pressure magnitude; (3) the three-bench method is the one that is most conducive to the stability of surrounding rock during the construction of soft rock tunnel in high geostress field and meeting the requirements of construction progress to a certain extent.
DAI Cong1,
3 HE Chuan2,
3 LIU Chuankun2 etc
.Model Test Study on Influence of Excavation Methods on Stability of Surrounding Rocks of the Soft Rock Tunnel in High Geostress Field[J] MODERN TUNNELLING TECHNOLOGY, 2020,V57(4): 141-149
2020, Vol. 57 