自由面对滚刀破岩机制影响的数值模拟研究

为了研究自由面对滚刀破岩机理的影响,运用UDEC方法建立了滚刀贯切岩石的二维数值系列模型,对TBM滚刀破岩过程进行了仿真。分析表明：在合理的刀间距和贯人度情况下,破碎坑自由面的存在使裂纹扩展能耗降低,裂纹密度增大,起裂方式增多,容易实现体积破碎,提高滚刀破岩效率。     

TB880E型掘进机刀具失效分析

秦岭隧道北口掘进机施15244m,掘进机所经过的岩层为混合花岗岩和混合片麻岩,属坚硬岩石．掘进机消耗刀圈1997个,比预计高出一倍多,根据原始计录,由于刀具失效,被更换刀具达五月把次（见表1）,刀具失效的形式有以下几种：1正常磨损刀具进行破岩时,破岩效率与其刃口宽度有关。随着刀圈磨损量的增加,刃口宽度增加,粉核区也逐渐增加,达到一定范围时会影响掘进速度,由于受到刀圈加工工艺的限制,而且新装刀圈与铲齿之间的高差为38mm,所以确定正滚刀与中心刀最大磨损量为38mm,此时粉碎区达50％左右;而边刀则因隧道直径（8800mr）以…     

Effect of replacing disc cutters with chisel tools on performance of a TBM in difficult ground conditions

A summary of a research program covering a period of two years on the performance of a TBM in a very complex and difficult geology is presented in this study. The formations in the study area varied from alluvium, sludge, mudstone, shale and limestone to quartzite with strengths from soft to very hard. The dykes frequently intruded the sedimentary rocks resulting in different degrees of weathering and fracturing in the country rock causing tremendous delays in progress rate of the TBM. The disc cutters started cutting inefficiently in clayey medium strength ground with extreme water income, at where also excessive disc consumptions started due to insufficient friction between the disc cutters and very soft (sludgy) formation, and it was decided to replace all disc cutters with chisel tools (ripper, scraper). Before making this important decision that could affect totally the excavation efficiency and production rate, some theoretical estimations were performed using the Evans’ cutting theory after some modifications based on the previous experimental studies for relieved cutting mode and wear flat, front ridge and vee-bottom angles found in complex shapes of chisel tools to estimate deterministically the torque and thrust requirements of the TBM.Field measurements of the torque and thrust requirements of the TBM equipped with the chisel tools validated the theoretical considerations and the deterministic model used for predicting the performance. Statistical analysis indicated that the model could be used reliably for performance prediction. This study also gave a unique opportunity to compare the performance of disc cutters and chisel tools used on the same TBM at variety of grounds and to analyze the effect of replacing disc cutters with chisel tools on the performance of the TBM. The field measurements indicated that the chisel tools were superior to the disc cutters in especially soft to medium strength rocks.     

掘进机刀盘滚刀间距对北山花岗岩破岩效率的影响实验研究

掘进机（TBM）开挖隧道过程中,其刀盘上滚刀间距设计的合适与否关系着破岩效率的高低。由于岩石非均匀、非连续、各项异性的特性,使用数值模拟方法研究滚刀破岩过程存在局限性。现场掘进实验主要是针对特定的掘进机做出机械运行参数优化,无法研究不同刀间距对破岩的影响。全尺寸滚刀破岩实验可以人为调整刀间距,且实验中采用大体积岩石可以避免尺寸效应的影响,因此受到了广泛的关注。采用北京工业大学自制的机械破岩试验平台,安装17英寸（432 mm）盘形滚刀,选取尺寸为1000 mm×1000 mm×600 mm的北山完整花岗岩试样,进行了5组刀间距的线性切割试验。实验中采集滚刀三向力,分层收集岩片且对其进行称重。对不同刀间距作用下的平均法向力、平均滚动力和比能进行了分析研究。当贯入度较小时,刀间距对平均法向力和平均滚动力的影响都不明显,随着贯入度的增加,刀间距对平均法向力和平均滚动力的影响增加。对于所有的刀间距而言,增加贯入度会产生更多的岩片,但并不一定会提高破岩效率,对于北山花岗岩而言,当刀间距与贯入度的比值为30左右时,比能值最低,此时破岩效率最高。     

Numerical modeling of the effects of joint orientation on rock fragmentation by TBM cutters

The performance of tunnel boring machines (TBM) highly depends on the fragmentation efficiency of the cutters. Many geological factors can influence the rock fragmentation process. In this study, a series of two dimension numerical modeling were performed using the discrete element method (DEM) to explore the effect of joint orientation on rock fragmentation by a TBM cutter. Results show that the joint orientation can significantly influence the crack initiation and propagation as well as the fragmentation pattern, and hence affect the penetration rate of the TBM. Such observations are also noted by laboratory and site studies. It also indicates that discontinuum-based DEM has the potential in simulating rock indentation and fragmentation by TBM cutters when rock joints are taken into consideration.     

围岩分类在TBM滚刀寿命预测中的应用

预测滚刀寿命,根据刀具磨损规律把握最好的换刀时机对隧道掘进机（TBM）来说是极其重要的.文章以秦岭隧道为例,应用围岩分类来预测刀具消耗量.根据影响TBM掘进率的岩石单轴抗压强度、岩石耐磨性、岩石硬度及岩体节理发育程度对围岩TBM工作条件等级的划分,定性分析了围岩等级与刀具消耗量的关系.在此基础上,提出围岩等级数的概念,得出不同的等级数与其相应的耗刀量之间的定量关系.     

双护盾TBM施工隧洞围岩分类方法及应用

针对引水隧洞围岩,在现有规范关于隧洞围岩分类基础上,提出了围岩分类新方法,综合考虑TBM掘进机掘进参数变化、围岩与护盾(管片)之间的间隙、出渣量、弃渣的块径、渣块形状、百分量、渣中刀具破岩新鲜面与围岩中结构面的比例、渣中软硬岩比例等因素,应用于达坂引水隧洞的围岩分类,所提出的方法具有重要的工程应用价值。     

Assessing the ability of rock masses to support block breakage at the TBM cutter face

In order for tunnel boring machines to efficiently cut or break rock, it is necessary that the block of rock in contact with the cutter be adequately supported by the surrounding rock mass. This support is provided by the interlocking of blocks and the friction of the surfaces. If blocks are inadequately supported or become free without breakage the result can be jamming at the TBM face. Such blocky ground conditions are typically assessed according to the spacing and orientation of discontinuities (including joints) within the rock mass, typically using a rock mass classification system. In laboratory tests on cuttability or abrasivity of rocks, test samples are typically supported securely in a frame or jig. Numerical models of rock breakage also assume boundary conditions in which the sample is completely supported. Therefore the applicability of the results from laboratory and numerical studies depends on the same degree of support of blocks in the ground. The conditions required to adequately support a block for breakage are investigated and related to rock mass parameters, in particular, the three-dimensional patterns of discontinuities. A rock mass can be capable of providing adequate support to a block of rock such that the cuttability is adequately described by conventional methods. However, there are some rock mass conditions where support of blocks is not well developed, potentially resulting in otherwise unexpected poor TBM progress or jamming of TBM with loose blocks. Three-dimensional discontinuity patterns can be assessed using stereographic methods or borehole (α–β) methods. It is proposed that problematic conditions may occur where: two or more oblique (α between 20° and 70°) discontinuity sets are present (and over-represented relative to a uniform distribution); one or more of these discontinuity sets are dipping into the opening (β = 180° ± 90°) and additional discontinuities (in sets or randomly oriented) are present to form complete tetrahedral wedge blocks.     

不同围压及切削顺序对TBM刀具破岩机理的影响

在综合考虑围压及刀具切削顺序的前提下,利用二维离散单元法建立双把TBM刀具切削节理不发育岩石的仿真模型,模拟出岩石裂纹的生产与扩展全过程。根据获得的裂纹扩展形态以及破碎块形成规则,总结归纳出四种典型破碎模式,并从刀具破岩效率、岩石裂纹扩展能力以及岩石破碎块度三个方面对刀具破岩机理进行进一步研究。仿真结果表明:随着围压的增加,刀具的破岩效率与裂纹扩展能力降低;同时加载方式下破岩效率比先后加载方式要大,而裂纹扩展能力则刚好相反;岩石破碎块度与破碎模式有关。     

复合岩体的TBM破岩机理数值模拟

为了指导TBM刀盘刀具的研制和不同地质条件下刀盘刀具的选型,TBM破岩机理的研究成为核心。在TBM滚刀的作用下,岩体中裂纹的生成、扩展和连接规律是深刻理解TBM破岩机理的前提,因此,TBM滚刀破岩机理的研究具有重要的工程应用价值。目前,TBM滚刀破岩机理的研究主要集中在单一岩体中,但在TBM施工过程中会遇到各种复杂的地质条件。笔者采用离散元方法,研究了复合岩体的破岩机理,复合岩体中岩片的形成不同于单一岩体,其裂纹的最终连接是由起裂于复合岩体交界面上的微裂纹的扩展,将两滚刀之间的赫兹裂纹连接,最终形成岩片。因此,在一定情况下复合岩体更有利于TBM隧道施工。     

不同围压条件下TBM刀具破岩模式的数值研究

为了研究不同围压条件下TBM刀具在掘进施工过程中的破岩机理,基于2-D离散单元法,利用UDEC仿真软件建立了双把TBM刀具侵入岩石的仿真模型。在此基础上设计了一组数值试验,成功地模拟出了不同围压条件以及不同刀间距下岩石裂纹生成,扩展和岩石破碎的全过程。仿真结果表明：TBM刀具作用下岩石存在四种基本的破碎模式,它们的出现与围压以及刀间距有关;破碎模式对刀具的破岩效率,岩石破碎块度均有影响;随着围压的增加,最优刀间距增大,但围压超过一定值后,最优刀间距反而减小。     

Theoretical prediction of wear of disc cutters in tunnel boring machine and its application

Predicting the cutter consumption and the exact time to replace the worn-out cutters in tunneling projects constructed with tunnel boring machine (TBM) is always a challenging issue. In this paper, we focus on the analyses of cutter motion in the rock breaking process and trajectory of rock breaking point on the cutter edge in rocks. The analytical expressions of the length of face along which the breaking point moves and the length of spiral trajectory of the maximum penetration point are derived. Through observation of rock breaking process of disc cutters as well as analysis of disc rock interaction, the following concepts are proposed: the arc length theory of predicting wear extent of inner and center cutters, and the spiral theory of predicting wear extent of gage and transition cutters. Data obtained from 5621 m-long Qinling tunnel reveal that among 39 disc cutters, the relative errors between cumulatively predicted and measured wear values for nine cutters are larger than 20%, while approximately 76.9% of total cutters have the relative errors less than 20%. The proposed method could offer a new attempt to predict the disc cutter's wear extent and changing time.     

Analysis on the damage behavior of mixed ground during TBM cutting process

Accurate prediction of rock cutting forces of disc cutters is especially significant for the design and construction of tunnel boring machine (TBM). Through the analysis of motion trajectory of TBM disc cutters, a three-dimensional model of rock breaking process of disc cutters is established. In terms of the rock strain which is resulted from the interaction between disc cutters and rock during the process of rock breaking, a three-dimensional cutting forces model is proposed with disc cutters set at certain parameters and in certain sizes. Subsequently, the equation of contacting forces between rock and disc cutter is derived. Moreover, a new method has been presented for the study of the rock breaking theory of the disc cutter and it also provides guidance for the design and application of TBM in tunnel excavation. The three-dimensional model for the rock breaking mechanism is used for predicting the cutting force for the situation of mixed ground.The damage field and the rock failure zone induced by disc cutter for mixed ground are also discussed in this study. In detail, the rock damage zones are divided into two parts, one is the left damage field which located in the outside of disc cutter. The other is the right damage field which located in the outside of disc cutter. The influence of the rock ground dip on the rock failure zone was also studied by parameter analysis.     

不同刀具配置下隧道掘进机高效破岩机理与推力预估

为解决隧道掘进机刀盘刀具破岩的安全性、可靠性、高效性这一隧道掘进机施工难题,从高效破岩机理和刀盘刀具与围岩耦合作用规律两个方面进行了研究,对单刀及多刀破岩理论体系进行了完善。结合理论分析和滚刀岩机作用综合实验台上的实验结果,提出了红砂岩、石灰岩和花岗岩等3种常见岩石的最优破岩刀间距,并给出了当岩石强度位于40～170 MPa之间时的最优刀间距计算式。综合考虑各种因素对隧道掘进机总推力、刀盘扭矩的影响,提出了复合式隧道掘进机总推力、刀盘扭矩估算的理论公式。通过工程实例验证,该理论计算式具有较高的科学性和精确性。研究成果可直接用于刀具选型布置、推力、扭矩设计,从而降低隧道掘进机的制造成本、提高施工效率。