钢筋混凝土非均质特性对金刚石钻头钻进与磨损机理的影响研究

Because of the requirement for national economic development and the limitation of reinforced concrete’s durability, construction about building and repairing reinforced concrete structures are both important in modern China. However, heterogeneity of reinforced concrete is the key factor which affects diamond drilling efficiency in the abovementioned construction. Therefore, quantitative evaluation model is proposed according to the concrete coordinating proportion and intensity difference of reinforced concrete in this study. Based on abrasiveness tests, SVM (support vector machine) regression is used to establish a prediction model of reinforced concrete. After indoor drilling tests, morphology features and grain size distribution of drilling cuttings, miro-shear marks on hole bottom face, wear types of bit matrix, as well as failure modes of diamond are considered to establish diamond cutting modes in nonhomogeneous materials, and to study the stress concentration and release phenomenon of diamond at the junction of different materials. Besides, the effect mechanism of drilling cuttings, diamond stress state and drilling technology to bit matrix wear and diamond failure are studied on the basis of drilling tests. Real-time data about drilling parameters, rate of penetration and drilling power are acquired during row-hold drilling tests, so as to find the relationship between reinforced concrete’s drillability and its heterogeneity properties. Research achievements in this study can provide theoretical foundation to diamond bit design and manufacture, and it is important to improve drilling efficiency, save economic cost and reduce environmental pollution.

受国民经济发展需求与钢筋混凝土耐久性限制的影响，我国已进入钢混结构新建和修复改造并重阶段，而钢筋混凝土非均质性是影响金刚石钻头施工效率的关键因素。为此，本项目从钢筋混凝土配合比和各组分材料强度差异进行考虑，提出非均质性定量评价模型，并通过研磨性测试和支持向量机回归方法建立钢筋混凝土的研磨性预测模型；通过室内微钻试验，对钢筋混凝土钻屑形貌和粒径分布、孔底微切痕、胎体磨损类型以及金刚石失效形式进行测试分析，建立单颗金刚石在非均质材料中的切削受力模型，研究金刚石在不同强度材料交界处发生的应力聚集与释放现象，揭示钻屑、金刚石受力状态和钻进工艺对钻头胎体磨损和金刚石失效形式的影响机理；对排钻试验的钻进参数、机械钻速和钻进功率进行实时监测，利用碎岩比功法建立钢筋混凝土材料非均质性对其可钻性的影响模型。研究成果可为金刚石钻头设计制造提供理论依据，对提高钻进效率、节约经济成本和减少环境污染等具有重要意义。

我国自20世纪80年代初开始大规模兴建钢筋混凝土结构，受其使用寿命的影响，目前正处于钢混结构新建与修复改造并重阶段，而金刚石钻头在其施工过程中发挥着重要作用。然而生产实践表明，金刚石钻头在钻遇钢筋时的机械钻速仅约为其在混凝土中机械钻速的十分之一，严重影响施工效率和生产成本，并产生更多的粉尘和噪声污染。..本项目针对钢筋混凝土材料的非均质特性，对其开展非均质性定量评价。在此基础上，设计和制作钢筋砼试样用以开展钻孔试验和研磨性测试，分别研究钢筋类型和布筋密度等因素对钢筋砼材料的可钻性和研磨性影响。对钻孔试验后的金刚石钻头唇面进行形貌观测，并结合薄壁钻头钻进特点，分析金刚石钻头钻进钢混混凝土结构时的磨损机理。同时，采用Autodyn模块的SPH粒子算法对单颗金刚石切削钢筋混凝土材料进行数值模拟，研究不同试验条件下非均质材料的破坏过程，以及金刚石的受力状态。研究结果表明，钢筋混凝土材料的可钻性随着混凝土强度等级和布筋密度的增加而显著提高。在混凝土强度等级和布筋密度一定时，金刚石钻头在钻进带肋钢筋混凝土时相较于光圆钢筋的平稳性更好，且机械钻速更高，但钻头胎体磨损量会少量增加。钢筋混凝土的研磨性随混凝土强度等级、碎石分布密度和布筋密度的增大而提高，但其显著性依次降低，且带肋钢筋混凝土的研磨性比光圆钢筋更强。数值模拟结果表明钢筋混凝土材料在切削过程种会产生明显的材料屈服强度和应变差异，导致不同材料会逐渐分离成独立个体，并导致金刚石在切削过程中受到“压应力-拉应力”的循环加载，易促使金刚石局部或整体破坏，从而影响钻头使用效果。..金刚石钻头在钢筋混凝土结构的新建、修复与改造，及质量检测等方面应用前景非常广阔，但钻头使用效果是限制其推广应用的关键因素之一。本项目开展钢筋混凝土非均质特性对金刚石钻头钻进与磨损机理的研究，可为优化金刚石钻头结构与制造工艺提供可靠的理论依据，对于提高钻进效率和缩短施工周期等具有重要意义。