矿山支护工程混凝土湿式喷射颗粒回弹及沉积行为研究

The springback of shotcrete used for support in mines wastes precious shotcrete material, pruduces a mass of dusts, breaks supporting strength and reduces work efficiency, at the same time, the high-speed particles generated in the process of shotcrete threatens the support workers. At present, the researchs on wet shotcrete springback theory and the sedimentation mechanism of shotcrete layers mainly focus on related gunshot, velocity and jet diameter calculated by qualitative analysis or applied formula. Nevertheless, it is still very short of the research on the whole procedure of shotcrete including jet structures, velocity profile, springback and depositing behavior. The project regards mining wet shotcrete as a research object, independently develop “Particle impact rebound test bench of wet shotcrete ” and “Jet structure testing system”. According to experimental determination and theoretical analysis and numerical modeling, wet shotcrete jet structure is studied and springback influence factors is quantified. The motion morphology of shotcrete particles and the whole process of springback are studied by using high-speed camera system from “shot” to “deposit”. The model of particle energy loss, particles rebound criterion and calculating model of springback speed are established. The evolution law of rebound trajectories and deposition behavior of particles are discussed after mixing admixtures and fiber. Finally the validity of theory calculation and simulation is verified by full size concrete injection test bench. The research can enrich shotcrete theory and improve the control effect of shotcrete springback.

矿山混凝土支护作业的喷射回弹不仅浪费了宝贵的湿喷物料、产生了大量的粉尘、破坏了支护强度、降低了工作效率，同时喷射冲击形成的高速颗粒对支护作业人员带来了威胁。目前对混凝土湿式喷射回弹理论和喷射层沉积机理的研究主要以定性分析或应用公式来计算有关射程、速度和射流直径为主，而对喷射射流结构、速度场、回弹及沉积行为的全过程研究仍非常匮乏。本项目以煤矿湿喷为研究对象，自主研制“喷射混凝土颗粒撞击回弹实验台”和“射流结构测试系统”，通过实验测定、理论分析和数值模拟，研究湿喷射流结构、量化回弹影响因素；利用高速摄像系统研究混凝土骨料颗粒自“射出”到“沉积”的运动形态和回弹发生的完整过程，建立颗粒能量损耗模型、颗粒回弹判据和回弹速度计算模型；探讨外加剂、纤维掺入后颗粒回弹运动轨迹和沉积行为特征演化规律；通过全尺寸混凝土喷射试验台验证理论、模拟结果的正确性。本研究可丰富混凝土湿喷理论，提高喷射回弹控制效果。

矿山混凝土喷射回弹浪费湿喷物料、产生粉尘及降低工作效率。针对湿喷混凝土射流结构、喷射回弹机理等关键科学问题，开展了湿喷混凝土水泥浆体和单颗粒粗骨料撞壁回弹实验、回弹影响规律实验、颗粒射流的数值模拟等实验；并对喷射工艺参数进行优化分析。根据湿喷水泥浆体撞壁后形态特征变化，得到了“水泥浆体”颗粒附壁回弹影响因素，建立了浆体附壁力学模型；并通过数值模拟研究得到了铺展系数影响因素多元回归方程。采用CFD-DEM耦合模拟混凝土颗粒流撞壁回弹特性，获得了高压气流（连续相）的动压和速度变化规律；阐明了颗粒（离散相）运动轨迹、速度场分布以及颗粒碰撞力学行为特征，揭示了影响湿喷混凝土射流稳定性的因素。开展了湿喷混凝土流变性能影响喷射回弹特性试验，建立了多元线性回归的湿喷混凝土回弹预测模型；验证了能量损失与喷射混凝土回弹率之间的良好线性相关性；得到了骨料颗粒在湿喷混凝土喷层的分布规律。基于以上实验及模拟研究，开展了不同风压、喷距下的湿喷混凝土喷射回弹实验，系统研究了湿喷混凝土回弹受风压、喷距的影响规律。本项目全面系统研究了湿喷混凝土撞壁回弹机理及影响规律，为解决井巷湿喷混凝土喷射回弹控制问题提供理论及技术支持。