基于离散元建模的盾构刀具磨损评估及其影响研究

柯  钊

摘 要

随着城市化进程的加快，地球上人类聚居的城市正在变得越来越拥挤，土地资源日趋紧张，越来越多的城市正在加快地下空间开发的步伐。在我国，地铁、地下公路、地下商业综合体及综合管廊等重要的城市大规模地下基础设施工程正在经历或者即将迈入建设高峰。新工法支撑的新型结构形式，以及采用新技术对传统工法实施创新升级，成为正在铺开的“新基建”的大势所趋。盾构法因其快速、经济、环保、自动化程度高等优点，近二十多年已经成为我国隧道与地下工程建设的最重要工法之一。然而，盾构机在地下掘进时会遭遇各类地层，特别是在并不鲜见的高磨蚀性砂性复合地层中，因其软硬不均、磨损阻力大等特性，盾构掘进刀具磨损极为迅速，且在刀盘上的磨损分布并不均衡。刀具若磨损更换不及时，会导致周围刀具超载负荷加速磨损，盾构掘进效率降低，甚至不得不停工。刀具的磨损状态如何快速准确评估，以及换刀时机如何科学高效决策，目前已经成为盾构掘进控制中的一个难题，在现在越来越多的14米直径以上的超大直径盾构施工中，尤其如此。目前，能够实现盾构刀具磨损快速精准评估的方法与技术，还很欠缺，并且磨损刀具的存在对其他服役刀具的影响规律仍有待进一步研究，

鉴于此，本文基于对在役刀具的三维数字化重建和离散元数值分析方法对磨损刀具对其他服役刀具的影响进行了初步的量化研究，主要研究成果包括：

（1）利用微软Kinect深度相机和自主研发的解析算法，围绕某盾构隧道工程现场获取的盾构磨损刀样本，对盾构磨损刀具实施了快速的三维数字化模型重建，获得了盾构刀具点云模型，通过与该刀型新刀设计数字化模型的比对，实现了盾构刀具磨损的全表面量化评估。结果显示，盾构掘进的刀具磨损，在单一刀具表面，不同区域差异较大，就磨损量来说，仅有小部分区域磨损量较大，大部分区域的磨损不到10mm。

（2）基于3DMax、EDEM等商业建模与数值分析软件的组合使用，首先，建立了盾构施工中含在役掘进刀具的刀盘3D数字模型；其次，针对砂性地层高磨蚀的工程特性与散体材料特性，采用了离散元法，建立了砂性地层中的考虑刀盘刀具与砂性土介质相互作用的盾构掘进离散元数值仿真模型，初步模拟了盾构机掘进施工中刀具在切削磨蚀性砂性土时的磨损过程，首次实现了在数值模型中对既有磨损刀具与新刀任意混编工况的离散元模拟。

（3）离散元数值模拟结果显示，盾构在散体材料介质中，尤其是在高石英矿物含量的砂性地层中，在同等约束条件下，磨损刀具的存在，会导致盾构刀盘上其它在役刀具在相同时间段内的磨损增加，且相同刀盘径距的刀具，其磨损增幅会大于不同径距刀具磨损增幅。随着刀盘上磨损刀具数量的增多，其它在役刀具磨损增加的边际效应有递减趋势。但总体来说，磨损刀的存在，虽然会一定程度上增加其它在役刀具的磨损量，但是增加的幅度并不显著。此外，除了加速其它在役刀具的磨损，磨损刀的存在也会较大幅度增加盾构掘进所需的能量。数值模拟的结果，通过与理论磨损公式的对比，验证了离散元法在模拟此类砂性地层中盾构掘进问题的有效性。

关键词：Kinect ；离散元；盾构刀具磨损；磨损影响

Abstract

With the acceleration of the urbanization process, cities on the earth where human settlements are becoming more and more crowded, land resources are becoming increasingly tense, more and more cities are accelerating the pace of underground space development. In China, large-scale underground infrastructure projects in major cities such as subways, underground highways, underground commercial complexes and integrated pipe corridors are experiencing or are about to enter the peak of construction. The new structural form supported by the new construction method and the use of new technologies to implement innovation and upgrade of the traditional construction method have become the trend of the “new infrastructure”. Shield method has become one of the most important construction methods for tunnel and underground engineering construction in China in the past two decades because of its advantages of rapidity, economy, environmental protection, and automation. However, the shield machine will encounter various stratums during underground tunneling, especially in the high-abrasive sand composite stratums, due to the characteristics of uneven hardness and high wear resistance, the shield cutters wear extremely fast and the wear distribution on the cutter is uneven. If the cutters are not replaced in time, it will lead to the accelerated wear of the surrounding cutter, shield tunneling efficiency will reduce, and even the shield has to stop working. How to quickly and accurately assess the wear state of the cutter, and how to make scientific and efficient decisions on the timing of cutter change, has become a problem in shield tunneling control. At present, the methods and technologies that can achieve rapid and accurate assessment of the wear of shield cutters are still lacking, and the influence of worn cutters on other service cutters still needs further study.

In view of this, based on the three-dimensional digital reconstruction of in-service cutters and the discrete element numerical analysis method, this paper conducted a preliminary quantitative study on the impact of worn cutters on other in-service cutters. The main research results include:

(1) Using the Microsoft Kinect depth camera and the self-developed analytical algorithm, around the shield wear cutter sample obtained on the site of a shield tunnel project, in this paper, the rapid three-dimensional digital model reconstruction of the shield wear cutter is realized. The point cloud model of the cutter is compared with the digital model of the new cutter to realize the full surface quantitative evaluation of the shield cutter wear. The results show that the cutter wear of shield is very different on different areas in a single cutter surface. In terms of the wear, only a small part area is large, and the wear of most areas is less than 10mm.

(2) Based on the combined use of 3DMax, EDEM and other commercial modeling and numerical analysis software, firstly, a 3D digital cutterhead model in shield construction is established; secondly, aimed at the highly abrasive sand stratums, the discrete element method was used to establish a shield tunneling 3D discrete element numerical model, and get a preliminary simulation of the abrasion process of cutters during cutting of abrasive sandy soil. For the first time, realized the discrete element simulation of the arbitrary mixed knitting condition of the existing wear cutter and the new cutter in the numerical model.

(3) The numerical simulation results of discrete element show that the shield is in the bulk material medium, especially in the sandy stratum with high quartz mineral content. Under the same constraints, the presence of worn cutters will cause increased wear of other in-service cutters on the cutterhead. And the cutters with the same radius installed on the cutterhead will have a greater increase in wear than the cutters with different radius installations. As the number of worn cutters on the cutterhead increase, the marginal effect of increased wear on other in-service cutters gradually decreases. But overall, although the presence of worn cutters will increase the wear of other in-service cutters, the increase is not significant. In addition, in addition to accelerating the wear of other in-service cutters, the presence of worn cutters will also greatly increase the energy required for shield tunneling. Through comparison with the theoretical wear formula, the results of the numerical simulation verify the effectiveness of the discrete element method in simulating shield tunneling in such sandy formations.

Keywords：Kinect; Discrete element; Shield cutter wear; Wear effect