Calculation model of the equivalent spiral shear stress of conditioned sand

Li, Xingchun; Tan, Nanlin

doi:10.1371/journal.pone.0212923

Cited by 4 publications

(4 citation statements)

References 13 publications

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“…According to the parameters of the earth pressure balanced shield screw conveyor used in Beijing Metro Line 14, the company was commissioned to process the scale shield screw conveyor at a ratio of 1:10, as shown in Fig. 5 36 . The experiment material is the ISO stand sand manufactured by Xiamen Iso Standard Sand Co, Ltd.…”

Section: Laboratory Testsmentioning

confidence: 99%

Theoretical analysis and experiment of pressure distribution and pressure gradient of shield screw conveyor: Taking sandy soil as an example

Yang

Jin

et al. 2020

Sci Rep

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rotation speed of the screw conveyor). The test results are directly related to the screw conveyors of different sizes (ie, the measuring results are affected by the spiral structure parameters). (2) When the appropriate parameters are input (that is, the conditioned soil is a plastic fluid and the shear stress is the constant), the proposed theoretical model can accurately predict the linear distribution of the pressure field gradient along the spiral direction. Whether the pressure field gradient is increasing or decreasing is controlled by the shear stress of the conditioned soil. The pressure gradient of the plastic fluid-like conditioned soil along the spiral from the soil inlet to the soil outlet will decrease linearly; When the conditioned soil is too hard, that is, the shear stress between the conditioned soil and the spiral structure is too large, the screw conveyor will become clogged, and the pressure field shows an increasing trend along the spiral direction. (3) The shield screw conveyor in the project is provided with front and rear gates. The influence of the opening of the gate on the pressure field distribution of the conditioned soil in the spiral pipe is not considered in the theoretical model and the model screw conveyor. This is also one of the contents to be considered in the next research work. (4) The conditioned soil pressure field distribution and pressure gradient calculation method proposed are derived on the assumption that the soil filling rate is 100% and the conditioned soil is a homogeneous plastic fluid. At the same time, for simplicity and practicality, the shear stresses between the soil and the screw structure are equivalent to a parameter, and it is assumed that the shear stresses along the helical axis remain the same. As for the true variation of the shear stresses around the helical structure, it is still unknown.

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Section: Laboratory Testsmentioning

confidence: 99%

Theoretical analysis and experiment of pressure distribution and pressure gradient of shield screw conveyor: Taking sandy soil as an example

Yang

Jin

et al. 2020

Sci Rep

Self Cite

View full text Add to dashboard Cite

show abstract

“…This test evaluates the suitability of conditioned soil to be extracted from a pressurized chamber by a screw convey or. The first attempt to simulate this condition was done by Merritt and Mair [26] and similar devices have been used by Vinai et al [10] and Rivas et al [27] and Li and Tan [28]. The device developed by Vinai et al [8] is com posed of a big tank where the conditioned soil is pressur ized and a screw conveyor with an upward inclination of 30°.…”

Section: Screw Conveyor Extraction Testmentioning

confidence: 99%

Soil conditioning in EPB shield tunnelling – An overview of laboratory tests

Peila

Martinelli

Todaro

et al. 2019

Geomechanics and Tunnelling

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The application of full‐face mechanized tunnelling, mainly with EPB shielded machines, has widely increased in the last years and today it can be considered the key technology when tunnelling in soils above and below the water table. The applicability range of EPB machines has widened thanks on one side to the technological and mechanical progresses and on the other side to the quality and effectiveness of the conditioning products. No recognized standards are available for laboratory testing of conditioned soil and each research centre has developed its own procedures and methods. In this paper, an overview of the most frequently used procedures is presented and discussed briefly.

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“…Reasonable determination of the water flow and water pressure in the screw conveyor is of great significance in solving the problem of spewing. Shield model test and numerical simulation are effective methods to analyze the mechanism of spewing, some scholars have studied the transportation of soil in shield structure through model tests [15][16][17][18] and CFD [10,19,20], and the results show that the water pressure distribution within the screw conveyor under steady state seepage is approximated as one-dimensional seepage.…”

Section: Introductionmentioning

confidence: 99%

Analytical study of EPB shield spewing discrimination in auxiliary air pressure mode

Zheng,

Yu,

et al. 2023

Preprint

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Considering the effect of auxiliary air pressure on the shield seepage field, the spewing problem is analyzed by using an analytical method. Soil conditioning is currently the main method that can be used to prevent and control the occurrence of shield spewing, but there is a lack of research on how low the soil permeability coefficient should be conditioned. To further study the mechanism of the occurrence of spewing, this paper uses the variable separation method and the superposition principle to derive an analytical solution of the two-dimensional seepage field of the shield under the auxiliary air pressure mode, and calculates the critical permeability coefficient of spewing based on a previous study. The accuracy of the analytical solution is verified by comparison with numerical simulations. Parametric analyses show that when the auxiliary air pressure fluctuates at the lower design limit, it slightly helps to avoid spewing, but as the auxiliary air pressure becomes greater than the water pressure at the bottom of the cutter face, the risk of spewing will be greater than that of the closed mode. After the water pressure at the bottom of the cutter face is greater than 28m, the critical permeability coefficient of a typical size shield will be less than 10-4cm/s, and the empirical way of controlling the permeability coefficient to 10-4~10-3cm/s has a risk of spewing. By comparison with the spewing example, the prediction of the critical permeability coefficient of spewing by the analytical solution is proven to be effective.

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Calculation model of the equivalent spiral shear stress of conditioned sand

Cited by 4 publications

References 13 publications

Theoretical analysis and experiment of pressure distribution and pressure gradient of shield screw conveyor: Taking sandy soil as an example

Theoretical analysis and experiment of pressure distribution and pressure gradient of shield screw conveyor: Taking sandy soil as an example

Soil conditioning in EPB shield tunnelling – An overview of laboratory tests

Analytical study of EPB shield spewing discrimination in auxiliary air pressure mode

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