盾构切削扰动下砂卵石颗粒空间运移传力特征及压力平衡控制研究

A lot of problems may encountered when the Earth Pressure Balance shield machine tunneling in sand and gravel stratum, such as cutter tool wear dramatically, soil tank pressure is difficult to control and the stratum is easy to collapse, etc., which not only seriously affect the tunnel construction process, but also cause great harm to the surrounding environment and adjacent structures. In this project, theoretic analysis, numerical simulation and model test will be adopted comprehensively to study the issues on the space transportation and force transfer characteristics of sand and gravel particles caused by shield cutting disturbance and its earth pressure balance control. Firstly, from the point of mesoscopic view of geotechnics, the evolution law of meso structure of sand gravel particles under cutting load of shield is analyzed, and further reveals the failure mesomechanics of stratum at excavation face. Secondly, under the condition of material transfer, a multiscale motion model is established to simulate the two-phase flow of solid particle and liquid in soil cabin. It can be used to analyze the spatial migration deposition law and load transfer mechanism of sand and gravel particles, furthermore, the spatial dynamic distribution law of soil pressure field in the cabin can also be obtained. Finally, a multi-variable optimization model is established to control earth pressure at the excavation face. In this model, the curved surface normal vector of soil pressure field in cabin is selected as target variable, and the rotation speed of screw conveyor is considered as optimal variable. In this way, the multi-system coordinated control of tunneling face stability can be realized.

土压平衡盾构机在砂卵石地层掘进时，存在刀盘刀具磨损严重、土舱压力难以控制、地层容易坍塌等问题，不仅严重影响了隧道施工进度，而且还对周边环境及邻近结构物造成极大危害。本项目采取理论分析、数值模拟和模型试验相结合的方法，开展盾构切削扰动下砂卵石颗粒空间运移传力特征及压力平衡控制研究。首先，从岩土细观角度出发，分析刀盘刀具切削荷载下砂卵石颗粒细观组构演化规律，揭示开挖面地层失稳破坏的细观机制；其次，建立物质转移条件下土舱内固-液两相颗粒流动的多尺度运动仿真模型，分析砂卵石颗粒空间运移沉积规律及荷载传递机制，得到土舱压力场的空间动态分布规律；最后，建立以土舱压力场曲面法向量为目标变量、以螺旋输送机转速为寻优变量的多参数优化模型，控制土舱内泥土压力与掘进面前方地层压力相均衡，实现对掘进面稳定的多系统协同控制。开展本项目的研究，不仅具有重要的学术价值，而且还可为盾构施工提供必要的理论指导和技术支撑。

砂卵石土是一种典型的力学不稳定地层，盾构在其中掘进时频发事故，主要原因就在于尚未能从本质上认识盾构刀盘与岩土体颗粒间动态交互作用、颗粒物质转移及其流动规律、砂卵石颗粒荷载传递机制以及对土舱压力的有效控制。.为获取能准确反映材料宏观力学特性的描述颗粒间相互作用的细观接触参数，采用筛分试验和大型三轴剪切试验得到砂卵石土的级配特性和抗剪强度参数，然后基于支持向量机、渣土改良试验、离散元虚拟试验对砂卵石颗粒间待定接触参数（恢复系数e、静摩擦系数μs及滚动摩擦系数μr）进行反演分析。.为研究盾构在砂卵石地层中的施工扰动问题，首先基于极限分析法的上限原理构建盾构开挖面失稳的三维旋转破坏模型，利用开挖面临界破坏时外力所做功与土体内部耗散功相等的原理，推导极限状态下出现开挖面失稳的极限支护压力。随后，构建刀盘切削砂卵石颗粒的三维离散元仿真模型，分析在刀盘切削荷载作用下砂卵石颗粒细观组构演化规律，揭示开挖面渐进性失稳破坏的细观机理。.为研究土舱内部改良土体颗粒运移传力性状，基于离散单元法对流塑状的以卵石颗粒为骨架的多颗粒集合体在粒子力和接触力作用下的流动规律及接触力链更迭特征进行模拟。获取土舱隔板压力分布，揭示了土舱隔板压力与刀盘前方支护压力的映射关系，给出了0.4~0.7的荷载传递系数，并提出土舱内部结构优化措施。.建立了包含土箱、刀盘和盾构机的大型离散元仿真模型和物理模型试验装置，模拟刀盘与砂卵石土体的动态交互作用，研究刀具数量、推进速度、螺旋机转速对土颗粒运动规律、地表位移、刀盘扭矩及正面阻力的演变规律，建立以土舱压力场曲面法向量为目标变量、以螺旋输送机转速为寻优变量的多参数优化模型，实现对掘进面稳定的多系统协同控制。.开展本项目的研究，不仅具有重要的学术价值，而且还可为盾构施工提供必要的理论指导和技术支撑。.通过本项目的研究，已发表学术论文9篇，获批软件著作权1项，获省部级奖1项，培养博士、硕士4人。

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