【作者】 武力；

【导师】 屈福政；

【作者基本信息】 大连理工大学 ， 机械设计及理论， 2009， 博士

【摘要】 土压平衡盾构掘进机是国家基础建设、资源开发和国防建设急需的重大技术装备。密封舱压力的设置和控制直接关系到开挖地层的稳定、刀盘刀具的磨损和盾构掘进效率。针对目前盾构施工密封舱压力分布规律认识不清、密封舱压力控制缺少完备的力学模型的问题,本文以离散元数值分析为主要研究手段,结合实验和施工数据验证,提出了改性土等效离散元模型及其参数反演方法,揭示了盾构掘进界面压力与密封舱隔板压力的映射关系、掘进参数与密封舱隔板压力的映射关系,为盾构施工密封舱压力控制提供机理模型,同时丰富和完善了离散元模型参数确定方法。离散单元法模拟盾构密封舱土压力系统工作过程的首要内容是改性土的模拟。以某地铁标段施工地层的砂土为原状土,根据实际施工改性剂的添加比例,在实验室配制了改性砂土并进行了改性砂土的坍落度实验和直剪实验;提出了改性砂土的等效离散元模型,在此基础上建立改性砂土坍落度实验和直剪实验的离散元数值实验模型。通过不同配比改性土坍落度实验和直剪实验的数值实验结果与实际实验结果相比较,证明在选取适当的等效模型参数的情况下,提出的改性砂土等效离散元模型能够模拟改性砂土的流动特性和抗剪强度特性。正确确定改性土等效离散元模型参数是离散元模拟盾构密封舱土压力系统工作过程的关键。将神经网络、遗传算法、三轴实验和离散元数值模拟相结合,用于改性砂土等效离散元接触模型参数反演。反演目标是改性土三轴实验离散元数值模拟得到的主应力差和轴向应变曲线以及径向应变和轴向应变曲线与真实实验曲线误差最小,采用的求解策略是基于遗传神经网络的参数识别。三轴实验的离散元数值模拟为网络提供训练样本,遗传算法和BP梯度下降算法优化网络的权值,改性土室内三轴实验的实际测量曲线为参数反演提供依据。通过反演预测的三轴实验结果与实际实验结果相比较,证明了反演方法的有效性,为改性砂土等效离散元模型参数确定提供依据,为密封舱土压力系统离散元仿真模型建立奠定基础。以某地铁标段施工的土压平衡盾构机为研究对象,建立了盾构密封舱土压力系统离散元仿真的几何模型;根据盾构掘进过程中密封舱工作原理,提出盾构隧道不同埋深下掘进界面压力的模拟方法,以及掘进面生成颗粒、螺旋出口删除颗粒的改性土在密封舱中动态传输过程的模拟方法,确立了密封舱土压力系统离散元仿真模型的边界条件;通过密封舱隔板土压力的离散元仿真结果与实际施工检测结果相比较,验证了仿真模型的有效性和仿真结果的正确性,为进一步的密封舱压力控制机理模型建立奠定基础。在密封舱土压力系统离散元仿真模型基础上,研究了辐板式刀盘和辐条式刀盘两种情况下,隧道埋深分别为10m、15m和20m时的密封舱压力分布规律,建立密封舱隔板压力分布的数学模型;得出在盾构刀盘结构形式一定的条件下,掘进界面等效压力与密封舱隔板等效压力为比例关系的结论,将密封舱隔板等效压力与掘进界面等效压力的比值定义为压力传递系数,给出了压力传递系数与刀盘开口率的经验公式,为盾构掘进密封舱隔板压力的设定提供理论基础。在密封舱土压力系统离散元分析模型的基础上,通过改变开挖面颗粒生成个数和螺旋转速,模拟盾构掘进的不同工况,得到单位时间盾构开挖量(推进速度)、排土量(螺旋转速)与密封舱压力变化率的对应数据;分析不同推进速度和螺旋转速下的密封舱压力变化情况,研究推进速度对密封舱压力变化率的影响、螺旋转速对密封舱压力变化率的影响;建立出土率与密封舱压力变化率的数学关系,为盾构掘进密封舱压力控制提供参考模型。更多还原

【Abstract】 The earth pressure balance (EPB) shield tunneling machine is the important technical equipment for infrastructure projects, resource development and national defence. The pressure balance control between the chamber and the ground at the excavation face is the key for tunneling safely and efficiently. Aiming at the problems that the satisfying mechanical model for the chamber pressure control is absent, in this work, the relation between the pressure on the excavation face and the pressure on the chamber board as well as the relation between the pressure on the chamber board and the working parameters are established, by the discrete element method (DEM) simulation, theoretical analysis and experiment validation, which not only provides the mechanical models for the chamber pressure control in tunneling, but also enriches the DEM model parameters determination method and extends the DEM engineering application.The first problem for DEM to simulate the work process of the chamber system of the EPB shield machine is the modeling of the conditioned sands. Taking the sands in a subway section as the original sands, and according to the proportion of the additives volume to the earth volume, the conditioned sands is reproduced and the slump test and the direct shear test are implemented in the laboratory. The equivalent discrete element model of the conditioned sands is provided, on the basis of which the DEM numerical model of the slump test and the shear test of the conditioned sands are established. By comparing the numerical results of the slump test and the direct shear test of the conditioned sands with different proportions to the corresponding laboratory test results, it is illustrated that the proposed DEM equivalent model can simulate the flow characteristics and strength characteristics of the conditioned sands on the condition that the proper DEM parameters is selected.The key for simulating the work process of the chamber system correctly is the determination of the equivalent DEM model parameters of the conditioned sands. The inversion method combining the genetic neural network and the discrete element simulation of triaxial tests is proposed for determining the contact model parameters of the conditioned soil. The aim is to make the error of the simulation curves and the laboratory curves of the triaxial tests minimum. The parameters solution is based on the genetic neural network. The training samples of network are provided by the DEM simulation. The complicated nonlinear relation between the input and the output samples is mapped by the genetic arithmetic. The simulation curves calculated with the inversed model parameters match the laboratory curves well, which illustrates that the presented inversion method of the DEM parameters of the conditioned soil is feasible. It provides the basis of the model parameters determination of the conditioned sands for the chamber pressure analysis model.Taking the shield machine tunneling in a subway section as the research object, the DEM geometrical model for analyzing the chamber pressure of the shield machine is established. According to the work principle of the chamber of shield machine during the tunneling, the simulation method of the excavation face pressure under different buried depths, and the modeling method of the dynamic transfer process of the conditioned sands in the chamber system which generate particles on the excavation face and delete particles on the outlet of screw conveyor are proposed. On the basis of this, the boundary condition of the DEM model of the chamber system is determined. The numerical simulation results of the observed pressure on the chamber board are compared with the field construction data, by which the feasibility of the simulation method is validated. The model provides the basis for further pressure analysis and control model building of the muck chamber system.On the basis of the DEM model of the chamber system, the pressure distributions of the chamber under the tunnel depth of 10m, 15m and 20m for the board cutting wheel and the spoke cutting wheel are studied. The mathematical model of the pressure distribution in the chamber is proposed. The relationship between the pressure on the excavation face and the pressure on the chamber board is established, the pressure transfer coefficient (the proportion of chamber board pressure to the excavation face pressure) in which is defined as the function of the opening ratio of the cutting wheel. The results provide the basis for the setting of the chamber pressure during tunneling.On the basis of the DEM model of the chamber system, by changing the numbers of the generated particles at the excavation face and the rotate speed of the screw, the different working conditions during EPB machine tunneling are simulated. The corresponding data of the pressure changing rate of the chamber under different excavation volumes per unit time (thrust speed) and the discharge volumes (the rotate speed of the screw) are obtained. The influence of the thrust speed and the screw rotate speed on the changing rate of the chamber pressure is studied respectively. The function of discharge rate and the changing rate of the chamber pressure is established, which provides the reference model of chamber pressure control for EPB machine tunneling.更多还原