Research On Construction Control Technology Of Larger Rectangular Cross-section Pipe Jacking Used In Shenzhen Metro Line 10

In order to alleviate the pressure of ground traffic in science and technology park of Shenzhen,to connect the Bangxuegang Science and Technology park with the Huawei Station of Metro Line 10,the Municipal Government of Shenzhen decided to build a 975 m underground connecting channel along Jiaxian Road.Because the building of the channel,first of all,the area of the main conflict between people and vehicles will be basically eliminated.Secondly,the channel realizes the seamless connection with the subway,which will make citizens be convenient to travel,and reduces the impact of bad weather on walking travel.Relying on the pipe jacking project of Huawei Station of Shenzhen Metro Line10,this paper studies the surface deformation,the increase of friction and the stress of pipe joints in the jacking process by using the measured data and numerical calculation.The main conclusions are summarized as follows:(1)According to the engineering geological conditions and the buried depth,when the average chamber earth pressure of the pipe jacking machine is controlled between 110 kPa and 150 kPa,during the construction,the longitudinal and lateral deformation of the surface can meet the design requirements.The analysis of the detection results of the lateral surface deformation shows that the maximum surface deformation generally appears above the central line,and gradually decreases with leaving the central line.(2)The theoretical calculation shows that,when the chamber earth pressure of pipe jacking machine changes,the influence is mainly manifested in the range of 1D near the central line(D is the cross-sectional length of the rectangular pipe section10.2m).Increasing chamber earth pressure can effectively reduce surface deformation,but excessive chamber earth pressure will increase the total amplitude of surface deformation in the construction process.Through comprehensive consideration,it is considered that it is appropriate to set the chamber earth pressure around 1.5 times of the theoretical calculation value(without considering groundwater)in this project.The increase of grouting pressure helps to reduce ground deformation,and the main influence area is about 10.2m near the central line.(3)The test data analysis shows that the friction resistance of the pipe section increases with the increase of jacking distance during jacking,but the average friction resistance decreases from 1350 kN to 900 kN,it illustrates that the growth relationship is not linear.In the construction process,when the pipe jacking machine passes through the medium coarse sand,the friction resistance of the pipe section increases greatly.The calculation results show that,when the buried depth of the tunnel is 1D(D is the cross-sectional length of the rectangular pipe section 10.2m).,the friction change calculated by the soil column theory is reasonable.When the tunnel depth is larger,the results calculated by the unloading arch theory are reasonable.(4)The results of field monitoring data show that the jacking force of No.31,No.55,and No.80 are about 61000 kN,41000 kN and 16000 kN.With the increase of jacking distance,it shows that the jacking force of section decreases gradually,which is caused by the friction.The calculation results of the interal force of the pipe section show that,under the condition of 0.2degree angle,the maximum stress is 78.4MPa with wood cushion,and is 105 MPa without wood cushion.The cushioning effect will be more obvious with the thickening of wood cushion.Under the condition of 0.2degree angle,the maximum stress of 0.8m thick pipe section is 61.4MPa,and the maximum stress of 0.65 m thick pipe section is 105 MPa,it illustrates that thickening the pipe wall can effectively reduce the maximum stress caused by angle.