About the author:

1.China Railway 15th Bureau Group Co., Ltd., Shanghai 200070, China; 2.Zhuhai Institute of UrbanPlanning & Design, Zhuhai, Guangdong 519000, China; 3.Guangdong Coastal Area Disaster Preventionand Mitigation Engineering Technology Research Center, Zhuhai, Guangdong 519000, China;4.Zhuhai Ruby Construction and Development Group Co., Ltd., Zhuhai, Guangdong 519000, China;5.College of Civil and Transportation Engineering, Shenzhen University, Shenzhen, Guangdong 518060, China

Abstract:

The stability of the shallow overburden soil section of the shield tunnel in the coastal soft soilarea is poor. To ensure the safety of shield construction, it is necessary to reinforce the soft soil layer.Focusing on the reinforcement effect of the three⁃axis mixing piles in the shield tunnels in the soft soillayer, considering two working conditions of unreinforced strata and grid reinforcement, the deformationand failure law of active and passive loadings of the shield tunnel excavation face and its influence onsurface displacement were compared and analyzed through numerical calculation. The results indicate thatthe horizontal displacement of the excavation surface and the vertical displacement of the surface aresignificantly reduced under the same support pressure after the shallow overburden section of the soft soilshield tunnel is reinforced by the triaxial mixing piles, and the deformation control effect is remarkable.There is a great difference in the evolution process of the excavation face under load between the gridreinforced strata and the natural unreinforced strata,which is mainly manifested in the distribution ofhorizontal displacement of the excavation face, the variation law of surface vertical displacement withsupport pressure, and the different ultimate failure modes