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

Abstract

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.

Experimental Verification of Torque Calculation Method for Shield Screw Conveyor

“…The driving torque and speed are collected by a torque sensor. The soil flow conveying angle is calculated according to Equation 11 in (Li et. al., 2020) [9].…”

“…The soil flow conveying angle is calculated according to Equation 11 in (Li et. al., 2020) [9]. The muck transfer rate is calculated based on the transportation situation in the excavation chamber.…”

Numerical investigation on the spewing mechanism of earth pressure balance shield in a high‐pressure water‐rich sand stratum

“…The earth pressure distribution and pressure gradient in a shield screw conveyor are two essential parameters to adjust the soil chamber pressure, reduce the ground settlement, and control the spewing at the outlet of the screw conveyor. Li et al (2020) established a theoretical model to calculate the pressure distribution and pressure gradient of a shield screw conveyor. With the slag element in the screw conveyor as the research object, they analyzed the influencing parameters.…”

Determination of the optimal working performance matching through theoretical analysis and experimental study for a screw conveyor

“…Karwat et al [ 12 ] studied the influence of the size of a DEM particle, coefficients of internal and external friction on conveying performance through experiments and simulations, the comparison of the results of the simulations and experiments gave satisfactory results. Li et al [ 13 ] conducted an experiment of pressure distribution and pressure gradient of shield screw conveyor with sandy soil. Owen et al [ 14 ] compared predicted mass flow rates with experimentally measured values.…”