| Subway is of great significance to greatly improve the efficiency of urban transportation,and the construction of urban subway tunnel in China is being carried out on a large scale.Shield construction has become an important construction method for urban subway construction due to its advantages of small disturbance to the stratum,small environmental impact and high construction efficiency.China has a vast territory and complex and changeable stratum conditions,among which sandy cobble stratum is a typical mechanical unstable stratum.Under the disturbance of shield tunneling,the stratum response is more sensitive,and the original relative stability or equilibrium state is easy to be damaged,resulting in formation loss and surrounding rock disturbance,resulting in ground subsidence and even collapse,endangering the adjacent buildings.In this paper,taking Guangzhou metro line 21 as the engineering background,considering the interaction between shield tunnel,soil and building,and by means of theoretical analysis,numerical calculation,monitoring measurement and other means,this paper studies the ground deformation law of shield construction in metro section and its influence on adjacent buildings.The main work and achievements are as follows:1.This paper summarizes the main research results of ground settlement caused by shield tunnel construction,analyzes the disturbance mechanism of shield tunneling on stratum in sandy cobble stratum,the formation reason of lag settlement and the mechanical behavior of soil disturbance in dynamic construction process of shield tunnel.2.Using Midas GTS NX finite element software,the engineering case of shield side crossing pile raft foundation is simulated and analyzed.The results show that: in the process of shield tunneling,the comprehensive shape of the surface transverse settlement groove curve is "V",the maximum settlement is 11.8mm(located in the center of the two tunnels inclining to the building side),the maximum horizontal displacement caused by shield tunnel construction is 4.82mm(moving to the side of the excavation free face);the maximum uplift of the tunnel invert bottom is 28.26 mm,the maximum settlement of the vault is 25.58 mm,and the left side of the tunnel is the left side The maximum lateral displacement of the soil on both sides of the right side is 11.42mm;the soil heave in a certain range in front of the cutter head and the soil behind the cutter head are 0.8mm,1.2mm and 0.6mm away from the center of the tunnel on the side of the building,1.2mm and 0.6mm near the center of the tunnel on the side of the building,and the maximum settlement values are 9.87 mm,11.8mm and10.4mm respectively;after the shield machine passes,the building foundation is close to the tunnel The maximum settlement is 5.4mm on the side of the tunnel.The maximum settlement is 0.4mm at the side far away from the tunnel,and then 0.2mm rise is produced due to the inclination of the building to the tunnel side.The inclination rate of the building is 0.00043,which is in line with the settlement control standard of the building.In the process of driving construction,the stratum change of the center of the two tunnels axis is the most obvious.3.Through the simulation and analysis of the influence of different jacking forces on the formation deformation,the corresponding settlement law is obtained.When the jack thrust is100 k PA,110 k Pa,120 k Pa and 130 k Pa,the maximum surface settlement is 10.63 mm,10.76 mm,11.8mm and 12.41 mm respectively,and the jacking force has little influence on the variation range of surface settlement;the maximum uplift value of soil in front of shield cutter head is 0.58 mm,0.82 mm,1.08 mm and 1.34 mm respectively.The larger the jacking force is,the greater the uplift value of soil in front of cutter head is,and the soil mass at the bottom of tunnel invert is with the excavation of shield tunnel,the settlement value and lateral displacement value of building foundation increase continuously,and their development trend and increase situation are basically similar.4.When the grouting pressure is 110 k Pa,150 k Pa,190 k Pa and 230 k Pa,the maximum horizontal surface settlement values are 12.7mm,11.8mm,7.44 mm and 6.32 mm,respectively.When the shield tunnel passes through the building side by side,with the increasing of grouting pressure,the longitudinal settlement and lateral displacement of the building decrease.When the grouting pressure is greater than 190 k Pa,the influence of grouting pressure on the settlement and deformation of buildings is very small.5.When the elastic modulus of grouting fluid is 5GPa,10 GPa,15GPa and 20 GPa,the lateral settlement values are 13.56 mm,11.8mm,11.18 mm and 10.54 mm,respectively.When the elastic modulus of grouting fluid is 5GPa,the settlement trough is in the shape of "V".The maximum value of surface settlement lies in the range between the two tunnel axes.When the elastic modulus of grouting fluid is 10 Gpa or above,the settlement trough is in "W" shape,and with the increase of the elastic modulus of grouting fluid,"W" shape appears The more obvious,the maximum value of surface settlement is located near the axis of the tunnel on the side of the building.With the increase of the elastic modulus of grouting fluid,the settlement value and lateral displacement value of building foundation decrease continuously. |
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