砂卵石地层盾构刀具微观磨损机理及寿命预测

Sandy cobble brings serious abrasion to shield cutters. The exchange for the cutters would be carried out frequently when the cutters are wear and tear, which will play a significant role in construction of cost and time, sometimes even lead to the safety accident. The research on the cutter wear for TBMs in the sandy cobble condition has barely adopted the micro abrasive， most research focused on the gross feature of the cutter wear. In this research, the study would be performed based on the micro abrasive method and the cutter life prediction model in this stratum would also be established. The sandy cobble is made up of mixture of cobbles and sands in the laboratory. The cutter wear tests are carried out, and the relationship between factors, including the different pebble features (particle and strength), cutter patterns, tunneling parameters (total thrust and cutter head velocity) and cutter wear would be studied via the tests. The plastic removal and fracture removal are adopted to analyze the cutter wear in the sandy cobble condition. The ratio of the two micro removal types is obtained based on the cutter wear test results. The cutter wear life prediction model would be induced by coupling the two micro abrasive wear mechanisms, and specific project verification cases would be carried out. Achievements obtained in this research can provide theoretical references for the cutter wear life prediction and exchange in the sandy cobble stratum.

砂卵石地层盾构刀具磨损严重，刀具磨损后频繁换刀影响盾构隧道施工成本和工期，甚至威胁施工安全。现阶段砂卵石地层刀具磨损研究仅针对刀具磨损宏观特征进行定性分析，缺乏微观磨损机制方面评价及预测。因此，拟开展砂卵石地层盾构刀具微观磨损机理及寿命预测研究。采用砂卵石、卵砾石配置具有典型地层特性的砂卵石土，通过模型试验分析不同砂卵石特性（粒径、强度）、刀具类型及掘进参数（总推力、贯入度）条件下盾构刀具磨损特征及规律。基于磨粒磨损理论从微观上分析砂卵石地层刀具塑性去除机制与韧性断裂去除机制，通过模型试验磨损后刀具形貌确定两种微观磨损去除机制的比例，建立耦合塑性去除机制与韧性断裂去除机制的刀具磨损量寿命预测模型，并通过具体工程实例进行验证。研究成果可为砂卵石地层盾构刀具磨损预测和更换提供理论基础。

砂卵石地层盾构隧道掘进过程中刀具磨损一直是亟需解决的难题之一。前期研究主要针对砂卵石地层刀具磨损宏观尺寸方面研究较为常见，鲜有从微观角度方面进行研究。开展了砂卵石地层盾构机刀具微观磨损机理及寿命预测研究工作。基于摩擦学原理，分析了砂卵石地层刀具不同磨损机制的原理和作用条件。从微观角度分析得出，砂卵石地层对切削刀具产生磨损的主要机制为磨粒磨损和黏着磨损。通过回归分析建立磨损量与砂卵石地层颗粒级配制之间的相关关系，研究结果表明不均匀系数和特征粒径与刀具磨损量之间相关性较高。并基于此建立了基于不均匀系数和特征粒径的砂卵石地层磨损计算关系式。在刀具破岩力学模型和盾构机刀具掘进运动形态基础上，考虑磨粒磨损及黏着磨损等不同磨损机制，并结合砂卵石地层磨损系数，建立了砂卵石地层刀具磨损微观磨损预测模型。并选取具体工程实例进行验证，预测磨损磨损量与工程实测磨损量进行对比验证，平均相对误差小于15%，验证了预测模型的准确性。针对砂卵石地层刀具微观磨损预测模型，对预测模型中主要参数进行了敏感性分析，研究得出砂卵石地层中磨损系数随着不均匀系数和特征粒径的增大而增大，并且出现前期增大较快，后期增大趋势变缓。刀具的磨损量随着刀刃刃角的减小而减小，在一定范围内，随着刃角角度减小，刀具磨损量的减少程度越来越小。研究成果从微观角度揭示了砂卵石地层盾构刀具磨损的机理，为砂卵石地层刀具磨损预测和更换提供了理论基础。