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Influence of Cutting Tools on Filter Cake Formation during Slurry Shield Tunnelling
Jiahua Mao,Dajun Yuan,Dalong Jin,Shengnan Liu 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.6
The filter cake on excavation face would be destructed periodically by cutting tools during slurry shield tunneling. The broken filter cake has a risk for face stability. The influence of cutting tools on filter cake was studied in this paper. A slurry-soil interaction model based on a multiphase flow theory which considers the solid particles and fluid in slurry was developed. The whole process of slurry penetration and filter cake formation on the excavation face of slurry shield can be described by this model. The motion state of cutting tools can be combined with this model and the effect of cutting tools on the slurry-soil interaction and pressure transfer mechanism was analyzed. Subsequently, the comparative calculations were presented to discuss the influence of tunneling parameters and the design of cutting wheel on filter cake formation during slurry shield tunnelling. The results indicate that the total area of filter cake on excavation face increases with the decreasing of revolutions per minute of cutting wheel and shield machine advance rate. The area ratio of filter cake on the center of excavation face always larger than other zone due to the lesser amount of cutting tools within one track in the center of cutting wheel. The results can provide a better understanding of how to set the shield tunneling parameters and design the layout of cutting tools for the stability of tunnel face.
Face Stability Analysis of Slurry Shield Tunnels in Rock–Soil Interface Mixed Ground
Ping Lu,Da-Jun Yuan,Jian Chen,Dalong Jin,Jun Wu,Weiping Luo 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.6
When shield tunneling in rock-soil interface (RSI) mixed ground, maintaining the stability of the tunnel face is very challenging. This study aims at the investigation of the face stability of slurry shield tunnels in RSI mixed ground. A new apparatus was developed to simulate pressurized slurry supporting the tunnel face in centrifuge tests. The progressive failure of the tunnel face was triggered with slow decrease of slurry pressure. With two equivalent model tunnels of circular shape and semicircular shape, the variations of soil (water) pressure and the displacement field in front of the tunnel can be obtained simultaneously. The face failure was found to be a local collapse in the upper soil layer. The limit support pressure was picked out at the sudden change of the measured soil or water pressures. Then the classical wedge-prism model was introduced and modified to calculate the limit support pressure for slurry shield tunnels in RSI mixed ground considering the partial collapse. Numerical analysis was applied to verify the theoretical analysis and sensitivity analysis was performed to estimate the influence of different parameters on the theoretical solutions.