基于宾汉姆流体的土压平衡盾构螺旋输送机排土量研究

为确保土压平衡盾构掘进过程中有效控制排土量，须考虑螺旋输送机构造特征和渣土性质对其影响。将改良后流塑性状态的渣土假设为宾汉姆流体，并基于螺旋输送机构造沿其螺旋排土方向展开成一长条形的长方体排土模型的基础上推导盾构螺旋输送机的理论排土量计算公式。通过对排土量影响因素进行分析表明： 1）排土量受开挖面支护压力、渣土的初始剪切屈服应力影响较大，而受渣土的塑性黏度影响较小； 2）随着隧道埋深和开挖面支护压力的增加，改良渣土的流塑性降低。将该理论成果应用于指导广州地铁21号线浅覆土全断面砂土地层某区间隧道盾构掘进中的渣土改良，开挖面支护压力保持了稳定，地表沉降控制为5 mm。

Study of Muck Discharging Volume of Screw Conveyor of Earth Pressure Balance Shield Based on Bingham Fluid

The present study aims to effectively control the muckdischarging volume of screw conveyor during earth pressure balance(EPB) shieldtunneling. In addition, the effects of the structural characteristics of screwconveyor and soil properties are analyzed. The improved soil in a flow plasticstate is assumed to be a Bingham fluid and is expanded into a long rectangularparallel piped discharging soil model based on the screw conveyor structurealong its discharging direction. Accordingly, the formula for calculating thetheoretical muck discharging volume of the screw conveyor is deduced. Theanalytical results of the influencing factors of the muck discharge volume areas follows: (1) The muck discharging volume is significantly affected by thesupport pressure on the excavation face and the initial shear yield stress ofthe soil. However, it is less affected by the plastic viscosity of the soil.(2) The fluidity of the conditioned soil reduces with an increase in tunnelburied depth and the support pressure of the excavation face. These theoreticalresults are implemented in guiding soil conditioning during EPB shieldtunneling in the shallow overlying full face sandy soil layer ofGuangzhou metro line 21, resulting in a stable supporting pressure of theexcavation face and a small surface settlement within 5 mm.