Shield tunneling in saturated ground poses challenges due to the potential risk of ground collapse resulting from seepage force and inadequate support pressure.This study employed a laboratory model test and a theoret...Shield tunneling in saturated ground poses challenges due to the potential risk of ground collapse resulting from seepage force and inadequate support pressure.This study employed a laboratory model test and a theoretical validation to elucidate the mechanisms of face failure and subsequent ground collapse in saturated ground during slurry pressure-balanced shield(SPBS)tunneling operations.A slurry circulation system was developed to ensure steady shield tunneling and to replicate the phenomena of ground collapse.Investigations into shield tunneling parameters and ground responses,including soil pressure,pore water pressure,and surface subsidence,were conducted to understand the mechanisms of face failure and subsequent ground collapse.The theoretical solution for the critical collapse pressure of the tunnel face,based on the rotational failure mechanism,was validated through the comparison with the experimentally determined critical collapse pressure.The results indicate that:(1)appropriate adjustments of tunneling parameters are crucial for promoting filtercake formation,maintaining chamber pressure,and minimizing ground subsidence;(2)chamber pressure,soil pressure,pore water pressure,and ground subsidence are closely correlated with shield tunneling parameters and the formation of filter cake;(3)ground collapse follows a continuous failure mode due to the destruction of filtercake and the decrease in chamber pressure;(4)the soil pressure at the cutterhead is more sensitive to disturbances from shield tunneling than chamber pressure;and(5)experimentally determined critical collapse pressures is consistent with the theoretical solution of limit analysis.展开更多
Shield tunneling in urban underground space necessitates tight control over support pressure at the tunnel face and a thorough insight into ground collapse mechanisms.This study conducts a model test and a theoretical...Shield tunneling in urban underground space necessitates tight control over support pressure at the tunnel face and a thorough insight into ground collapse mechanisms.This study conducts a model test and a theoretical validation to clarify the mechanisms of face failure and subsequent ground collapse in sand during earth pressure balanced shield(EPBS)tunneling operations.The experiment investigates the changes in soil pressure and surface subsidence patterns during shield tunneling and collapse stages,to elucidate the entire process of ground collapse triggered by shield tunneling disturbances.A novel methodology was proposed to ensure effective verification of the rotational failure mechanism,focusing on the collapse pit morphology and the critical collapse pressure.The results indicate that:(1)precise control over the shield tunneling and screw conveyor rotation speeds is essential for tunnel face stability;(2)the sand with low moisture content is prone to stepwise ground collapse under shield tunneling disturbances;(3)soil pressure measurements at the cutterhead are more indicative of face failure and imminent ground collapse than those from the soil chamber;(4)there is a consistent alignment between the rotational failure mechanism and observed collapse pit morphology,albeit with slight variations due to tunneling disturbances;(5)the experimentally determined critical collapse pressure is higher than the theoretical prediction,indicating an underestimation of risks in the current model.The study advances the understanding of the face failure mechanisms in shield tunnels,thereby providing insights into the design and safety of shield tunneling within engineering practices.展开更多
基金support of the National Natural Science Foundation of China(Grant Nos.52179116 and 51991392)the support of Key Deployment Projects of Chinese Academy of Sciences(Grant No.ZDRW-ZS-2021-3).
文摘Shield tunneling in saturated ground poses challenges due to the potential risk of ground collapse resulting from seepage force and inadequate support pressure.This study employed a laboratory model test and a theoretical validation to elucidate the mechanisms of face failure and subsequent ground collapse in saturated ground during slurry pressure-balanced shield(SPBS)tunneling operations.A slurry circulation system was developed to ensure steady shield tunneling and to replicate the phenomena of ground collapse.Investigations into shield tunneling parameters and ground responses,including soil pressure,pore water pressure,and surface subsidence,were conducted to understand the mechanisms of face failure and subsequent ground collapse.The theoretical solution for the critical collapse pressure of the tunnel face,based on the rotational failure mechanism,was validated through the comparison with the experimentally determined critical collapse pressure.The results indicate that:(1)appropriate adjustments of tunneling parameters are crucial for promoting filtercake formation,maintaining chamber pressure,and minimizing ground subsidence;(2)chamber pressure,soil pressure,pore water pressure,and ground subsidence are closely correlated with shield tunneling parameters and the formation of filter cake;(3)ground collapse follows a continuous failure mode due to the destruction of filtercake and the decrease in chamber pressure;(4)the soil pressure at the cutterhead is more sensitive to disturbances from shield tunneling than chamber pressure;and(5)experimentally determined critical collapse pressures is consistent with the theoretical solution of limit analysis.
基金the support of the National Natural Science Foundation of China(Grant Nos.52179116 and 51991392)the National Key R&D Program of China(No.2021YFC3100802).
文摘Shield tunneling in urban underground space necessitates tight control over support pressure at the tunnel face and a thorough insight into ground collapse mechanisms.This study conducts a model test and a theoretical validation to clarify the mechanisms of face failure and subsequent ground collapse in sand during earth pressure balanced shield(EPBS)tunneling operations.The experiment investigates the changes in soil pressure and surface subsidence patterns during shield tunneling and collapse stages,to elucidate the entire process of ground collapse triggered by shield tunneling disturbances.A novel methodology was proposed to ensure effective verification of the rotational failure mechanism,focusing on the collapse pit morphology and the critical collapse pressure.The results indicate that:(1)precise control over the shield tunneling and screw conveyor rotation speeds is essential for tunnel face stability;(2)the sand with low moisture content is prone to stepwise ground collapse under shield tunneling disturbances;(3)soil pressure measurements at the cutterhead are more indicative of face failure and imminent ground collapse than those from the soil chamber;(4)there is a consistent alignment between the rotational failure mechanism and observed collapse pit morphology,albeit with slight variations due to tunneling disturbances;(5)the experimentally determined critical collapse pressure is higher than the theoretical prediction,indicating an underestimation of risks in the current model.The study advances the understanding of the face failure mechanisms in shield tunnels,thereby providing insights into the design and safety of shield tunneling within engineering practices.
