Chengshi guidao jiaotong yanjiu (Mar 2024)
Mechanism Analysis of Sand Splitting Grouting in Metro Tunnel
Abstract
[Objective] In the process of grouting in metro tunnel, there exists dynamic coupling effect between sand stress field and slurry flow field. In order to improve the design level of metro tunnel sand grouting, it is necessary to study the mechanism of sand splitting grouting under the coupling effect of slurry and sand. [Method] The splitting grouting diffusion process is simplified as a symmetric expansion process, and the basic characteristics of the slurry flow field are analyzed with Bingham fluid as the representative. The temporal and spatial variation equation of the splitting channel width and the slurry pressure is derived when the sand layer is treated as ideal linear elastic material and the elasticity is assumed to be homogeneous and isotropic. The basic law of sand splitting grouting is discussed by adjusting parameters such as slurry viscosity and sand stiffness. According to the basic law of sand splitting grouting under the coupling effect of slurry and sand, the sand splitting grouting under the coarse sand and silt soil layer in the section between Lanhua Rd. Station and Houbao Station of Chongqing Metro Line 10 phase II is verified on the spot, and the length of main and secondary slurry veins is obtained. [Result & Conclusion] The slurry pressure changes more sharply at the starting and ending stages of grouting, but is stable in the middle. Slurry viscosity and compression modulus of sand are important factors affecting the splitting diffusion law. The smaller the slurry viscosity and the compression modulus of sand, the larger the diffusion radius of the slurry becomes. While the larger the compression modulus of sand, the smaller the width of the splitting channel. Engineering verification shows that there is a 17%-22% deviation between the measured value and the calculated value, which indicates that the theoretical model has certain value for engineering application.
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