Measurement and analysis of vertical deformation of stratum induced by quasi-rectangular shield tunneling in soft ground
SI Jinbiao1,ZHU Yaohong2,JI Chang1,ZHOU Shunhua1
(1. Key Laboratory of Road and Traffic Engineering of the Ministry of Education,Tongji University,Shanghai 201804,China;
2. Ningbo Rail Transit Group Co.,Ltd.,Ningbo,Zhejiang 315101,China)
Abstract:The stratum deformation caused by the quasi-rectangular shield tunneling is different from the circular shield tunneling and the limited research has been carried out to study the issue. The first time application of the quasi-rectangular shield tunnel in soft ground in China was studied and the surface deformation and layered settlement were monitored and analyzed to investigate the major pattern of the vertical stratum deformation. The suggestions for the construction controlling were presented in terms of the deformation mechanism. The results show that the maximum surface settlement is about 50 mm and the range of excavation influence is about 20 m ahead of the excavation face. The vertical displacement of the ground surface experiences four stages over the tunneling period,the slowly down(upward) stage,the rapid upward stage,the rapid down stage and the gently down stage. The surface settlement occurs mainly after the pass of the shield tail,which is caused by the consolidation of the disturbed soft stratum. The main factors for the vertical stratum deformation include the chamber pressure,synchronous grouting and shield posture. The shield posture caused the soil on two sides of the shield machine to move in the opposite directions. In addition,the influence of the shield posture to soil deformation is more significant than in the case of single circle shield tunneling.