砂卵石地层土压平衡式盾构机的排土机制

For Earth-Pressure-Balanced shield machine, the efficient discharge of soil is one of the difficult points during driving. Generally, sandy cobble stratum has a high concentration of pebbles (including large boulders locally) and pebble has high compressive strength and strong permeability, therefore, the discharge of soil may face high wearing-away and it will be very difficult to transport, and easy to cause spewing, etc. The aim of this research application is to provide insight into the soil-discharging mechanism of EPB shield machine. To achieve this aim, the flowing discipline of soil particles will be studied during the conveying of soil in terms of both ribbon conveyer and shaft type screw conveyer theoretically and numerically, and the formulas for moving path and gestures of soil particles inside the conveyer will be established; the soil-discharging experiments will be carried out to analyze the soil pressure distribution and the pore water pressure distribution along the conveyer in conveying process, as well as the liquidity, plasticity and permeability resistance of soil and parameters of the conveyer that may affect the pressure distribution; based on the results of indoor experimental modeling and the monitoring data of the practical engineering, the soil-discharging parameters (including soil performance, driving velocity and soil-discharging velocity, etc.) needed by the EPB shield machine driving in sandy cobble stratum will be proposed to achieve efficient tunneling. Therefore, this application, especially now, has an important role in guiding the underground railway construction and the development and utilization of urban underground space under the condition of sandy cobble stratum, and it is very necessary and urgent for our country.

掘削渣土的高效排出是土压平衡式盾构机掘进所关注的重难点之一。砂卵石地层由于卵石含量高（含局部大漂石）、卵石抗压强度大且具有强渗透性，其渣土排放将面临磨耗高、排土困难、易诱发喷涌等难题。本项申请以探明砂卵石地层土压平衡盾构的排土机制为目标，采用理论分析与数值模拟研究轴式及带式螺旋出土器排土过程中渣土颗粒的流动规律，建立出土器内渣土颗粒运行轨迹及姿态的描述方程；采用排土试验研究排土过程中螺旋出土器渣土压力、孔隙水压力的沿程分布特性，探明渣土流塑性、抗渗性、螺旋出土器参数等因素对渣土压力、孔隙水压力沿程分布的影响；结合盾构机室内掘进模型试验和现场施工监测数据分析，提出满足砂卵石地层土压平衡盾构机高效掘进所需的渣土性能、推进速度、排土速度等排土参数。本项申请对于我国在砂卵石地层条件下的地铁建设和城市地下空间开发利用，具有重要的指导作用，并显得非常必要和紧迫。

在富水砂卵石地层中进行盾构掘进，砂卵石地层由于卵石含量高（含局部大漂石）、卵石抗压强度大且具有强渗透性，其渣土排放将面临磨耗高、排土困难、易诱发喷涌等难题，掘削渣土的高效排出是土压平衡盾构机掘进所关注的重难点之一。本项申请首先从细观层面入手，采用颗粒流程序PFC建立三维数值模型对土压平衡盾构砂卵石地层掘进排土机理进行了研究，分析了不同形式螺旋出土器的出土效率，同时针对不同粒径的卵石分析了带式与螺旋出土器扭矩、功率的变化规律及土仓内不同位置处土压力变化特征。在数值模拟的基础上，研制了土压平衡盾构掘进排土试验装置，通过室内试验对盾构出土效率及刀盘结泥饼的机理进行了研究，并进行了影响刀盘结泥饼因素的作用效应分析，通过测量千斤顶压力、刀盘扭矩、掘进速度等参数分析盾构掘进状态和出土效率，揭示了含水率、刀盘开口率、土仓压力对出土效率及刀盘结泥饼的影响规律，得到了满足砂卵石地层土压平衡盾构机高效掘进所需的渣土性能、掘进速度、排土速度等排土参数的变化规律；基于试验结果，从机械、人为操作等方面开展理论分析，研究了盾构机排土机制及刀盘结泥饼的原因，并依托实际工程探明了刀盘结泥饼硬化形成岩石的内在机理。采用流体力学数值计算方法实现了对盾构机内流动状态的数值模拟，探究了盾构机中渣土的流动情况，计算得到了盾构机各部位压力与速度的沿程分布情况。最后以广州地铁为依托，从理论分析、室内试验及现场测试等多方面对土压平衡盾构渣土改良技术进行了深入的研究，提出了渣土改良技术中泡沫性能的评价指标，得到了提高土压平衡盾构排土效率的方法，通过盾构施工现场的应用证明了渣土改良效果评价指标的合理性。本项课题的研究成果可以帮助建设者更深刻地认识砂卵石地层土压平衡盾构排土机制，对于我国在砂卵石地层条件下的地铁建设和城市地下空间开发利用具有重要的现时意义。