| Reasonable setting of slurry shield tunnel construction operation parameters is the key technology of slurry shield tunnel excavation engineering,but also to ensure the safety of slurry shield tunnel construction,reasonable slurry shield excavation construction parameters can not only reduce the surface settlement and other instability damage caused by the soil structure damage caused by slurry shield construction disturbance to a certain extent,but also improve the construction efficiency and safety of slurry shield Therefore,reasonable setting of slurry shield tunnel construction operation parameters is an extremely important process in slurry shield tunnel engineering.In this paper,FLAC3 D numerical simulation software is used to simulate the excavation of slurry shield tunnel in the Nanchang subway slurry shield tunnel example project,and the kriging proxy model is used to replace the complex slurry shield tunnel construction project,and the mathematical analysis method of kriging proxy model is used to realize the optimal prediction of slurry shield tunnel construction parameters in the construction process of complex slurry shield tunnel.To reduce the instability and damage caused by slurry shield tunnel construction,the law between the construction parameters and construction influence of slurry shield tunnel was explored,and the sensitivity and correlation analysis of construction parameters were carried out through the Kriging proxy model.The main research contents of this paper are as follows:(1)The formation of mud membrane is a key construction technology in the construction process of slurry shield tunnel,this paper explores the influence of mud penetration excavation soil under the action of 0.13 MPa,0.15 MPa and 0.17 MPa three different slurry tank pressures by carrying out indoor mud permeability to form mud film test,with the increase of slurry tank pressure,more solid particles in the mud penetrating into the soil layer,and the formation of mud film is more dense;The process of mud penetrating the soil layer to form a mud film during the construction of the mud shield tunnel was simulated.The triaxial shear test of the permeated soil layer of the mud was carried out,and the characteristic parameters such as the deformation modulus,effective cohesion and effective internal friction angle of the permeated soil layer were determined.(2)Through the joint Abaqus software and FLAC3 D software,the tunnel excavation mesh model of the mud-permeated soil layer was jointly established,and the tunnel excavation process of the slurry balance shield in the "soft upper and hard" mud-permeated soil layer was simulated,and the surface settlement and cutterhead center bearing bending moment difference caused by the construction of the slurry shield tunnel under different construction conditions were calculated,and the difference between the surface settlement and the cutterhead center bearing caused by the construction process of the slurry shield under different construction conditions was analyzed.The law of construction parameters and ground surface settlement and cutterhead center bearing bending moment difference is summarized,and the formula of simplified calculation of cutterhead center bearing bending moment difference is derived.(3)Collect and sort out the construction parameter data of slurry shield tunnel,use FLAC3 D software to simulate the excavation of slurry shield tunnel,calculate the difference between surface settlement and cutterhead center bearing bending moment caused by slurry shield construction,and confirm the optimization of four main construction parameters of slurry shield excavation,namely shield thrust,cutterhead torque,cutterhead speed and excavation speed;By using the kriging interpolation optimization algorithm of DACE toolbox kriging in Matlab software,the multi-objective construction parameter optimization kriging proxy model of slurry shield excavation is established,and the kriging proxy model is used instead of the complex calculation process of slurry shield,and the complex relationship between the four construction parameters and the construction impact is established through the kriging proxy model,so as to reduce the construction impact and optimize and predict the construction parameters of slurry shield machine.(4)Through the sensitive and correlation analysis of the construction parameters of the slurry shield tunnel,the construction parameters that have a great influence on the surface settlement and cutterhead bearing bending moment generated by the slurry shield were identified.Among them,the boring thrust has the greatest correlation with the bending moment of the cutterhead center bearing.The correlation coefficient is 0.8224,which is a positive correlation,followed by cutterhead torque,which has a correlation coefficient of 0.2447 with the bending moment of the cutterhead center bearing,which is also a positive correlation;and for surface settlement,the correlation coefficient between boring thrust and surface settlement is the largest,and the correlation coefficient value is 0.5403,which is a positive correlation,followed by the correlation coefficient between the excavation speed and the surface settlement is 0.2613,which is also a positive correlation,among the four construction parameters,the correlation between the excavation thrust and cutterhead torque and the bending moment of the cutterhead center bearing is large,and the correlation between the excavation thrust and excavation speed and the surface settlement is greater.When setting the construction parameters,the construction parameters of slurry shield with high correlation and sensitivity should be given priority and key consideration,and guiding the operators of slurry shield machine to reasonably set the construction parameters can improve the overall excavation efficiency and safety of slurry shield tunnel construction,which has important guiding significance for guiding the construction of slurry shield tunnel. |
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