Research On The Settlement Mechanism And Control Technology In The Construction Of Ultra-shallow Buried Vertical Stacked Utility Tunnel Crossing Expressway

The underground comprehensive pipe corridor is the trend of intensive construction of municipal pipelines,and also the direction of modernization of urban infrastructure.The use of multi-cabin parallel integrated tunnel corridors to integrate power,communications,gas,water supply,drainage and other municipal supporting pipelines into one,implementing unified planning,unified construction and management,can not only effectively solve the problem of repeated excavation caused by pipeline construction,Completely bid farewell to the situation of opening the "road zipper" at any time,rational and efficient use of underground space resources,and will also bring great convenience for the later maintenance and repair of pipeline network facilities.This thesis relies on the project as the municipal transportation supporting project of Beijing New Airport Airport Economic Zone-Yongxing Hebei Road Comprehensive Pipe Corridor Tunnel Project.The main pipeline tunnel and the branch pipeline tunnel of this underground tunnel project are vertically stacked,and have the characteristics of "multiple cabins,large span,shallow soil cover,poor self-stability of vault stratum".This article uses comprehensive research methods such as theoretical analysis,three-dimensional numerical simulation and on-site measurement,mainly conduct research on the following contents:1.The structural layout plan and construction plan of the main pipe gallery tunnel;2.The reinforcement scheme of the tunnel entrance from the slope into the tunnel;3.The evolution law and control technology of the ground settlement in the construction of the main pipe gallery tunnel;4.The construction scheme of the junction section of the branch pipe gallery tunnel vertically stacked with the main pipe gallery tunnel.Through comprehensive research and analysis,this paper draws the following main conclusions:1.In view of the complex transformation of the stress system and the discontinuity of structural waterproofing in the process of excavation and support of the conventional multi span multi arch tunnel structure,this paper puts forward the overall parallel tunnel layout of the independent cabin structure,which effectively solves the problems of the complex transformation of the stress system and the discontinuity of structural waterproofing.2.According to the engineering characteristics that the entrance of the tunnel into the tunnel is located on the slopes on both sides of national highway 106,the tunnel span is large,the stratum condition of the vault of the tunnel is poor,and the tunnel is covered with shallow soil,this paper puts forward a method of the entrance of the tunnel into the tunnel on the slope that conforms to the characteristics of the project,which is composed of steel reinforced concrete bearing arch,large pipe shed,bearing side wall and ground beam It can ensure the safety of the tunnel entrance from the side slope to the multi span tunnel.3.In this paper,three-dimensional numerical simulation method is used to simulate the construction of this project.Through the study,the advanced grouting reinforcement scheme with a thickness of 1.5m is determined,and the excavation scheme of each cabin,which is "from two sides to the middle(electric cabin 2 and gas cabin ? electric cabin 1 and north side of water cabin ? Water letter cabin ? south side of water cabin)",as well as the demolition scheme of the middle bulkhead of the water tank,which is "skip 12 m and demolish 6 m in sections",This scheme can effectively control the surface settlement and the distribution of plastic zone of surrounding rock.4.Because the branch pipe gallery tunnel of this project is close to the upper main pipe gallery,which is vertically stacked with the main pipe gallery tunnel.The environmental conditions of the construction site are complex and there is no condition to provide construction shaft.This paper studies and proposes the construction scheme of concealed multiple parallel shafts in the tunnel as the construction channel of the junction section of the branch pipe gallery tunnel,which not only effectively solves the construction difficulties Problems,and reduce the cost of the project.