Research On Key Construction Technology Of Super-Shallow Buried Large Section Rectangular Multi-Hole Parallel Pipe Jacking

Pipe jacking technology is a tunnel construction technology that combines continuous advancement of the tunnel face and continuous jacking and laying of pipe sections.This construction method has outstanding advantages such as time saving,high efficiency,safety,and low comprehensive cost.With the continuous advancement of urbanization construction and the continuous development of pipe jacking technology,the construction of pipe jacking tunnels has increasingly developed in the direction of heterosexual large-section,shallow overburden,long-distance and porous parallel tunnels,and has increasingly become my country’s urban subway entrances and exits.One of the main construction methods for the intersection of urban trunk lines.Relying on the tunnel project of Zhengzhou Hongzhuan Road passing through Zhongzhou Avenue,this paper studies the key technology of super-shallow buried and large-section porous parallel rectangular pipe jacking.The main work of the paper is as follows:(1)Aiming at the problem of excessive jacking thrust in long-distance and large-section pipe jacking tunnels,the method of using thixotropic mud and reasonably controlling grouting construction parameters in the jacking process can effectively reduce the excessive jacking thrust of long-distance and large-section pipe jacking tunnels.The big problem,in which the content of bentonite is 6%,the content of CMC is 0.1%,the content of soda ash is 0.3%,the content of PHP is 0.2%,and the content of water is 93.4%.The number and distribution of different grouting holes are arranged according to the size of the tunnel section,and the grouting pressure should be determined according to the formation pressure.(2)Aiming at the surface settlement problem of porous parallel smallspaced rectangular pipe jacking tunnels under shallow burial conditions,the overall construction sequence of multi-hole spaced jump holes is adopted,and the longitudinal spacing of adjacent tunnel excavation surfaces is controlled at 24 m,which can effectively eliminate porous parallel tunnels.The adverse effect of construction on the surface settlement,and at the same time,the construction efficiency is greatly improved;the dynamic control of the jacking thrust,the advancing speed,the excavation volume and the grouting pressure during the pipe jacking process also have an important impact on the surface settlement.In addition,the installation on the front foundation A set of anti-return device can effectively reduce the surface settlement of the pipe section and the machine head during the stable shutdown process.(3)The construction attitude control strategy of shield pipe jacking is proposed,which is mainly based on articulation rectification and grouting rectification,supplemented by double-screw excavation rectification,sixcutter control,and jacking cylinder control measures.Precise control of the attitude of a multi-hole parallel small-pitch pipe jacking tunnel.The hole door seal is optimized to the hole door seal form of two curtain rubbers and two hinge plates.At the same time,after the hole door seal completely wraps the pipe jacking machine,the thixotropic mud grouting is carried out in time to quickly form a mud sleeve and start the pipe jacking machine.The best sealing effect of the hole can be achieved by controlling the excavation speed of about 5mm/min..