Research On Construction Control Technology Of Rectangular Double-pipe-jacking Of Utility Tunnel Under Expressway

Since the new times,our country’s higher requirements for urban construction management planning have provided an opportunity for the development of urban integrated pipe corridors.The pipe jacking method construction technology has been favored due to its unique economic and social benefits.At present,there are more researches on single pipe jacking at home and abroad,but less research on double pipe jacking construction,especially for rectangular double pipe jacking.This article relies on a comprehensive pipe gallery in the capital area with double jacking pipes underpassing the expressway project,and expands the research on the basis of existing projects,Using methods such as theoretical analysis,field measurement and numerical simulation,Study the influence of the rectangular double pipe jacking construction under the expressway on the vertical displacement of the ground surface,Put forward ground settlement control measures based on site engineering practice.The research conclusions are as follows:(1)The disturbance mechanism of pipe jacking construction on the vertical displacement of the ground surface is: During the construction process,as the relative position relationship between the pipe jacking machine and the soil changes,different effects of squeezing,shearing,and unloading on the adjacent soil are produced.The nature of the soil is changed,and the soil is disturbed by deformation,which eventually leads to the change of the vertical displacement of the ground surface.(2)The perturbation law of pipe jacking construction on the vertical displacement of the ground surface is as follows: The influence range is generally 3-5 times the outer diameter of the jacking pipe.The vertical displacement change law of the ground surface can be divided into four processes: slight uplift phase,rapid subsidence phase,continuous subsidence phase,and stable phase.(3)Through the analysis of the measured data of the field monitoring,the influence of the two adjacent highways with different cross-sections on the vertical displacement of the ground surface is explored,and the mechanism and law of the influence of the pipe jacking construction on the vertical displacement of the ground surface are verified.(4)In the existing engineering practice,by using FLAC3 D software to simulate the different construction sequence conditions of the double different sections It was found that "excavation of large cross-sections first,then small cross-sections" has the smallest vertical displacement of the ground surface.Combined with field monitoring data,the rationality of the model is verified.(5)The influence of the different angles between the jacking pipe and the highway on the vertical displacement of the ground surface is simulated under the "big first and then small" condition.Under the included angles of 30 degrees,60 degrees and 90 degrees,the larger the included angle,the smaller the degree of influence on the vertical displacement of the ground surface,and the smaller the range of influence.(6)The effect of different spacings between double pipe jacks on the vertical displacement of the ground surface is simulated under the "large first,then small" condition.At 0.5,1m,8m and 16 m spacing,the larger the spacing,the smaller the impact on the vertical displacement of the ground surface,The greater the scope of influence.With the increase of the distance,the maximum value of the vertical displacement of the ground surface is continuously reduced,and the affected range is continuously enlarged,and the position of the maximum value of the vertical displacement gradually shifts to the side of the large cross-section pipe jack.