The Mechanical Behavior Study Of Intersecting Segment Of Shield Tunnel And Contact Channel

For the construction of the double-hole single-track shield tunnel section,when connecting channel construction,it is necessary to open in two parts of the continuous two-ring segment to meet the requirements of the construction of the contact channel in the tunnel.At the same time,the surrounding soil of the communication channel needs to be reinforced to meet the requirements of structural safety.Because the opening of the shield tunnel that has been built,the structure of the special annular segment at the opening has become very complex and becomes the weakest link of the entire shield tunnel.When the deformation and stress of the special annular segment of the shield tunnel are too large,the overall stability of the shield tunnel and its normal use function are often affected.The reinforcement effect of the surrounding soil around the gangway also has a direct impact on the safety of the structure and the stability of nearby functional water and sewage pipelines.Therefore,it is of great significance to analyze and study the special annular segments of the shield tunnel and the reinforcement of the connecting channel.This thesis uses theoretical analysis and ANSYS and FLAC3 D software for numerical simulation,and takes the cross section of the shield tunnel and connecting passage of Shijiazhuang Metro Line 1 as the actual engineering background.The analytical research of the special ring segments of the shield tunnel and the reinforcement of the connecting channel were carried out.It draws the following conclusions:(1)Comparing steel pipe pieces with concrete pieces in strength,rigidity and cost,it is concluded that although steel pipe pieces have more advantages than concrete pieces in terms of strength and rigidity.Considering the price of steel pipe pieces is higher than that of concrete pieces while thinking that the concrete segment also meets the safety requirements in terms of strength and rigidity.So it is recommended that the special ring segments at the intersection of the shield tunnel and the connecting passage in Shijiazhuang Metro Line 1 be made of concrete material.(2)The method of grouting reinforcement in the tunnel is suitable for the excavation of the communication channel.At the same time,the use of curtain grouting reinforcement is more effective than the reinforcement of the soil in the top 120° using small pipe grouting,and it also shows the importance of strengthening the face during the construction of connection channel.The contact channel excavation will have a greater impact on the surrounding soil layer.The main effect area on the surface of the earth is about the surface area between the shield tunneling,and effect is more obvious to the surface subsidence of the contact channel center(vertical and contact channel excavation).In the case where there are no other functional pipelines near the contact channel and no buildings on the ground,excavation of the communication channel may be considered to be reinforced by advanced small pipe grouting.According to the impact of the excavation of the Shijiazhuang Metro Line 1 between Zhaohuiqiao Station and Baifo Station Intersection Passage on the surrounding groundwater,sewage and other functional pipelines,surface settlement and the project cost requirements,it is recommended that the curtain grouting being used during the construction of the liaison passage reinforce the soil within 1m around it.(3)Due to the need to open a special ring segment for the excavation of the communication channel,stress redistribution occurs in the stratum near the opening,and the unfavorable stress form of the tension will be generated at the opening position,which is the weakest link of the entire main tunnel and has serious impact the shield tunnel stability.At the same time,the sequence of the excavation of the communication channel determines the degree of influence on the left and right main tunnels.The main tunnel on the side where the segment opening is cut first has a greater influence on the stress and displacement than the main tunnel on the side of the cut segment.Further analysis of the main effect of the opening of the special ring of the left shield tunnel was about 3.6 m and 7.2 m range of segments.(4)In the process of excavation of the connecting channel,temporary steel reinforcement measures for the shield tunnel segment were proposed,and it was concluded that the erection of the steel support on the segment is more conducive to the stability of the main structure of the shield than the absence of the steel support.After the excavation of the communication channel is completed,the vertical steel support exerted by the split ring is mainly subjected to pressure,and the lateral steel support is mainly subjected to tensile force.The steel supports are provided with 7 support points on the split ring,8 support points on the adjacent segment of the open ring and 9 support points on the open ring of the steel ring,and 10 support points on the adjacent segment of the open ring.The shield tunnel has the support and protection function.The stress and deformation of the segments are smaller than that of the unsupported steel support.However,the two groups have little difference in the support effect of the segment.