Influence Of Shield Construction On Soil Deformation Under Different Tunnel Spacing

With China’s economic and social development,the development of urban construction is changing with each passing day,infrastructure construction is becoming more and more perfect,people’s living standards are steadily improving,and more and more people are flowing to cities.The construction and development of underground transportation is the main method to alleviate the problems of ground traffic congestion and lack of land resources.Based on the background of Xinfadi Station ~ Caoqiao Shield Section of Section 08 of Beijing Metro Line 19,this paper establishes three models of tunnel spacing of 1.5 times,1.8 times and 2.0 times on the basis of actual working conditions.The simulation was conducted under the two working conditions of simultaneous excavation and double-track,and the following conclusions were drawn:(1)During excavation on the left line,single-line shield construction has little disturbance to the soil layer,soil deformation is concentrated on the top and bottom soil layers of the excavation tunnel,and the deformation area spreads from the vault to the surface,forming along the left line on the surface Settlement troughs distributed above the dome;when the left line excavation is completed,with the right line excavation,the double line construction causes the strength of the soil layer to weaken,the disturbances in the middle soil body overlap each other,and the deformation accumulates。(2)When excavating on a single line in succession,excavation at 1.5 times and 1.8 times the diameter of the hole will cause deformation of the soil around the left and right lines concentrated around the left line DB-0X-04,showing a single peak settlement groove curve;2.0 times The excavation of the hole diameter interval will form a deformation concentrated on the soil near the top of the left and right line arches,which is shown as a double-peak settling groove curve.(3)When digging at the same time with double lines,the deformation of the soil body spreads upward and downward from the arches of the left and right lines,and is concentrated and distributed below and above the midline between the left and right lines;during excavation,the left and right lines affect each other,causing the strength of the soil layer to weaken;the settlement curve of the surface measurement points is symmetrically distributed around the central axis of the two tunnels.(4)When double-tracking is carried out at the same time,the ground subsidence area advances synchronously but slightly lags.The excavation of the measuring point subsidence curve at 1.5 times and 1.8 times the diameter of the hole shows a single peak settlement,the peak is located along DB-0X-05 Nearby,the excavation with a pitch of 2.0 times the hole diameter shows a double-peak curve,with the peak near DB-0X-03 and DB-0X-07.