【作者】 孟庆琳；

【导师】 屈福政；

【作者基本信息】 大连理工大学 ， 机械设计及理论， 2012， 博士

【摘要】 EPB盾构在进行隧道施工时,实现密封舱内土压力根据施工要求及地质条件的变化自动进行动态平衡控制,可有效降低由于盾构施工引起的地表变形,从而降低事故发生的概率。掌握具有地质适应性的EPB盾构密封舱土压力动态平衡控制技术,对提高我国复杂掘进装备控制水平,具有重要的工程实用价值和战略意义,也是未来盾构技术发展的必然趋势。由于缺乏对EPB盾构螺旋输送机在复杂塑性挤出过程中压力与流动之间准确的数学描述,给密封舱土压力动态平衡控制带来困难。因此,EPB盾构螺旋输送机承压输送机理己成为密封舱土压力动态平衡控制亟待解决的重要课题。基于上述工程背景,本文针对EPB盾构密封舱土压力动态平衡控制中,螺旋输送机在复杂的塑性挤出过程中所表现出的承压输送特性展开研究。首先通过实验研究了密封舱土压力系统内改性土体的流变特性,实现了密封舱土压力系统工作过程的数值模拟,进而揭示了盾构螺旋输送机承压输送特性及控制参数对密封舱土压力的作用机理等被控系统特性,建立了密封舱土压力系统数学模型,提出一种基于模型参数在线辨识结合最优控制的EPB盾构密封舱土压力动态平衡控制方法。本文的主要研究内容包括以下几个方面：(1)提出了一种压力相关的Bingham粘塑性非牛顿流体粘度模型。基于自主研发的适合于EPB盾构改性土体流变特性研究的实验装置,对实验室重建的典型改性土体进行流变特性实验,发现了当围压不变时改性砂呈现出剪切稀化的非牛顿流体特性,剪切应力与剪切速率满足经典Bingham粘塑性流体本构关系,获得了典型配比下改性砂的流变参数的范围,并发现粘度系数和屈服应力均随围压的增大而增大,进而提出了一种压力相关的Bingham粘塑性非牛顿流体粘度模型。该模型的提出为密封舱土压力系统工作过程数值仿真研究奠定基础。(2)提出了CFD仿真环境下非牛顿流体压力相关的粘度模型及密度模型的自定义方法,实现了对EPB盾构密封舱土压力系统工作过程中改性土体粘-弹-塑性流动行为的数值模拟。与实验结果在压力场分布及流量等方面均具有较好的一致性。该结论为进一步采用数值仿真方法研究螺旋输送机承压输送特性及控制参数对密封舱土压力的作用机理等方面研究工作的展开奠定基础。(3)提出了EPB盾构螺旋输送机在复杂的塑性挤出过程中的排土效率计算方法。通过对密封舱土压力系统工作过程的数值仿真并结合理论分析的方法,研究了EPB盾构螺旋输送机进出口压差,所输送介质流变特性及螺旋输送机几何参数对排土效率的影响规律,揭示了螺旋输送机承压输送特性,提出了EPB螺旋输送机在复杂的塑性挤出过程中的排土效率计算方法。解决了建立密封舱土压力系统数学模型所涉及的关键问题。为密封舱土压力系统数学模型的建立奠定基础。(4)提出了一种基于模型参数在线辨识结合最优控制的密封舱土压力动态平衡控制方法。建立了EPB盾构密封舱土压力系统数学模型,考虑了密封舱内改性渣土的等效切线变形模量E1和螺旋输送机排土效率n与密封舱内土压力的相关性。建立了单独控制螺旋输送机转速与同时控制推进速度和螺旋输送机转速这两种控制模式下,EPB盾构密封舱土压力系统控制方程。基于优化方法根据实际施工数据在线辨识控制方程中参数矢量,解决了控制方程参数矢量受到施工地层地质条件的随机性和密封舱内介质改性处理的不均匀性等因素影响所具有的时变性问题,并取得较好的辨识结果。基于最优化控制策略获得了密封舱土压力系统控制的最优控制律,讨论了比例因子及模型参数矢量取值对控制效果的影响,给出两种控制模式间切换的依据,说明了双控模式下存在最优化的推进速度。在密封舱土压力模拟实验台上取得了较好的控制效果。更多还原

【Abstract】 During the tunneling of EPB shield, it is realized that the dynamic balance control of working chamber earth pressure of EPB shield according to construction requirements and variations of geological condition, which can effectively control the land deformation and reduce the probability of accident. There is important strategic meaning and important application value for improving control level of complex boring equipment to master the dynamic balance control technologies of working chamber earth pressure of EPB shield. It is also the inevitable trend for the development of the future shield technologies. The mathematical description between pressure and flow for screw conveyor of EPB shield under complex plastic extrusion process is absent, which leads to difficulty for the dynamic balance control of working chamber earth pressure of EPB shield. So the conveying mechanism of screw conveyor of EPB shield under pressure becomes as urgent topic to be resolved for the dynamic balance control of working chamber earth pressure.Based on the above engineering backgrounds, aiming at the conveying mechanism of screw conveyor of EPB shield under complex plastic extrusion process for the dynamic balance control of working chamber earth pressure, this paper firstly studies rheological behavior of conditioned soil, then this paper realizes the numerical simulation for the work process of the working chamber earth pressure system. The characteristics of controlled object such as the conveying properties of screw conveyor under certain pressure difference, the effect mechanism between control parameters and earth pressure are exposited. The mathematical model is established. The dynamic balance control method of geological adaptability based on the on-line identification of model parameters and the optimization control for the working chamber earth pressure is proposed.The main contents of this dissertation are as follows:(1) A new pressure-dependent improved Bingham viscoplastic non-newtonian fluid model is presented. Based on the developed decive which is used to study rheological behavior of conditioned soil of EPB shield, conditioned sands are reproduced and the rheological tests are implemented in the laboratory. When confining pressure constant, conditioned sands exhibit the non-newtonian fluid characteristics of shear thinning, and the relations between shear stress and shear rate correspond with Bingham viscoplastic non-newtonian fluid model. The ranges of viscosity coefficient and yield stress are obtained. Furthermore, the viscoplastic parameters increase with the increase of the confining pressure. A new pressure-dependent improved Bingham viscoplastic non-newtonian fluid model is defined for the CFD numerical simulations. The model provides the basis for the numerical simulation for the work process of the working chamber earth pressure system.(2) The pressure dependent viscosity model and density model of viscoplastic non-newtonian fluid is established by user-defined method in CFD simulation environment. The numerical simulation of soil flow characteristics such as viscosity, elasticity and plasticity for the work process of the working chamber earth pressure system is realized. The numerical simulation results of the observed earth pressure field and velocity field distribution in working chamber are compared with experimental results. It provides the basis for further researching on the conveying properties of screw conveyor under certain pressure difference, as well as the effect mechanism between control parameters and earth pressure by the numerical simulation method.(3) The discharge efficiency of EPB shield screw conveyor under complex plastic extrusion process is proposed. By theoretical analysis and numerical simulation for the work process of the working chamber earth pressure system, the effects of pressure difference and rheological behaviors of conditioned soils and geometric parameters on discharge efficiency of screw conveyor are studied. The conveying properties of screw conveyor under certain pressure difference are exposited. The problems during establishing mathematical model of the working chamber earth pressure system are solved. It provides the basis for further researching on the dynamic balance control of the working chamber earth pressure system.(4) A new dynamic balance control method based on the on-line identification of model parameters and the optimization control for the working chamber earth pressure is proposed. A new mathematical model of the working chamber earth pressure system is established. In the model, the effect of earth pressure in working chamber on equivalent tangent modulus of deformation Et and discharge efficiency of screw conveyor η are considered. The control equations of the working chamber earth pressure system under two kinds of control mode such as the separate control of screw conveyor speed, the combination control of advancing speed and screw conveyor speed are given respectively. Based on optimization method, the on-line identification according to the field construction data of the parameter vector in control equation is realized. By the on-line identification, the time-varying problem of the control equation parameter vector which is caused by the randomness of geological conditions and inhomogeneity of conditioned medium is solved. Based on the optimization control strategy, the optimal control law of the working chamber earth pressure control system is obtained. The influence of the scaling factor and values of the parameter vector on control effect is discussed. The switch basis between two kinds of control mode is given. The optimization of speed under the double control mode is existent.The ideal control effect is obtained on the working chamber earth pressure simulation experiment platform.更多还原