Key Control Techniques For Surface Settlement Of Shield Tunnel Undercrossing High Railway Base

With the rapid development and utilization of above ground and underground space resources,projects using tunnel shield tunneling to cross existing high-speed and intercity railways are constantly emerging.When shield tunneling passes through such projects,tunnel excavation will inevitably induce ground loss,leading to settlement and deformation of the upper roadbed.Once the deformation exceeds the allowable range of the roadbed,it will bring serious harm to the safe operation of the railway.In order to accurately predict roadbed settlement and effectively control this deformation,making it meet the requirements of safe operation,this thesis relies on the key project of China Railway Group to conduct research on key technologies for controlling surface settlement of shield tunneling through high-speed railway roadbed.The main research results are as follows:(1)Based on the theory of surface settlement prediction and taking a certain roadbed section of Shijiazhuang Metro Line 4 and Beijing Metro Line 14 as engineering basis,the influence of shield tunneling on the settlement deformation of the roadbed was studied without new reinforcement measures,and the correctness of the model was verified.(2)Conduct research on the displacement and deformation laws of existing reinforced components during shield tunnel underpass construction,analyze the stress and displacement deformation of each component,and use tunnel arch theory to verify the rationality of the deformation laws of pipe piles;The setting of construction joints in U-shaped grooves does not have a significant impact on the settlement deformation of U-shaped grooves,but can cause stress discontinuity at the edge of U-shaped grooves.(3)The reinforcement treatment of Shijiazhuang Metro Line 4 was carried out using different ranges of MJS horizontal rotary jet grouting method,and it was found that the reinforcement effect of the "door" structure is better than the "plate" structure.However,when the formation loss rate exceeds a certain degree,the MJS reinforcement method has no significant effect on controlling roadbed settlement.(4)Innovative application of capsuled grouting technology in the settlement and deformation control of shield tunneling through high-speed railway roadbed,active lifting control of roadbed settlement induced by shield tunneling during the construction process of Beijing Metro Line 14 roadbed.By analyzing the mechanism of capsuled grouting technology lifting roadbed settlement deformation,a prediction model for shield tunneling through roadbed settlement is proposed,and the principles of capsuled grouting are summarized,Applying this model to seven different homogeneous soil layers for grouting and lifting,the final results meet the requirements of settlement control,and the lifting effect is good.This process has certain applicable value.