Experimental study on the influences of cutter geometry and material on scraper wear during shield TBM tunnelling in abrasive sandy ground

When shield TBM tunnelling in abrasive sandy ground,the rational design of cutter parameters is critical to reduce tool wear and improve tunnelling efficiency.However,the influence mechanism of cutter parameters on scraper wear remains unclear due to the lack of a reliable test method.Geometry and material optimisation are often based on subjective experience,which is unfavourable for improving scraper geological adaptability.In the present study,the newly developed WHU-SAT soil abrasion test was used to evaluate the variation in scraper wear with cutter geometry,material and hardness.The influence mechanism of cutter parameters on scraper wear has been revealed according to the scratch characteristics of the scraper surface.Cutter geometry and material parameters have been optimised to reduce scraper wear.The results indicate that the variation in scraper wear with cutter geometry is related to the cutting resistance,frictional resistance and stress distribution.An appropriate increase in the front angle(or back angle)reduces the cutting resistance(or frictional resistance),while an excessive increase in the front angle(or back angle)reduces the edge angle and causes stress concentration.The optimal front angle,back angle and edge angle for quartz sand samples areα=25°,β=10°andγ=55°,respectively.The wear resistance of the modelled scrapers made of different metal materials is related to the chemical elements and microstructure.The wear resistances of the modelled scrapers made of 45#,06Cr19Ni10,42CrMo4 and 40CrNiMoA are 0.569,0.661,0.691 and 0.728 times those made of WC-Co,respectively.When the alloy hardness is less than 47 HRC(or greater than 58 HRC),scraper wear decreases slowly with increasing alloy hardness as the scratch depth of the particle asperity on the metal surface stabilizes at a high(or low)level.However,when the alloy hardness is between 47 HRC and 58 HRC,scraper wear decreases rapidly with increasing alloy hardness as the scratch depth transitions from high to low levels.The sensitive hardness interval and recommended hardness interval for quartz sand are[47,58]and[58,62],respectively.The present study provides a reference for optimising scraper parameters and improving cutterhead adaptability in abrasive sandy ground tunnelling.

Research on the design method for uniform wear of shield cutters in sand-pebble strata

During shield tunneling in highly abrasive formations such as sand–pebble strata,nonuniform wear of shield cutters is inevitable due to the different cutting distances.Frequent downtimes and cutter replacements have become major obstacles to long-distance shield driving in sand–pebble strata.Based on the cutter wear characteristics in sand–pebble strata in Beijing,a design methodology for the cutterhead and cutters was established in this study to achieve uniform wear of all cutters by the principle of frictional wear.The applicability of the design method was verified through three-dimensional simulations using the engineering discrete element method.The results show that uniform wear of all cutters on the cutterhead could be achieved by installing different numbers of cutters on each trajectory radius and designing a curved spoke with a certain arch height according to the shield diameter.Under the uniform wear scheme,the cutter wear coefficient is greatly reduced,and the largest shield driving distance is increased by approximately 47%over the engineering scheme.The research results indicate that the problem of nonuniform cutter wear in shield excavation could be overcome,thereby providing guiding significance for theoretical innovation and construction of long-distance shield excavation in highly abrasive strata.

刃宽对硬岩掘进影响的仿真及试验研究

滚刀在硬岩掘进中极易发生崩刃、偏磨等异常失效,研究硬岩掘进条件下刃型参数对滚刀破岩载荷和破岩效率的影响十分重要.本文采用滚刀破岩试验和仿真分析相结合的方法,从载荷曲线、破岩体积、破岩比能等方面分析了刃宽对滚刀破岩的影响.基于双线性本构模型及Benzeggagh–Kenane损伤断裂准则建立了岩石材料的内聚力本构模型,通过单轴抗压试验及巴西劈裂试验对内聚力本构模型的微观参数进行了校准,并进一步建立了滚刀破岩的内聚力仿真模型.结果表明:内聚力本构模型可以准确的模拟破岩过程中岩石裂纹的萌生和扩展过程.依据裂纹的萌生和扩展情况,滚刀破岩过程主要分为三个阶段:弹性阶段、裂纹萌生–扩展阶段及岩石破坏卸载阶段.滚刀破岩载荷和破岩体积随着贯入度、刀间距和刃宽的增加而增加;破岩比能随刃宽的增加呈先减小后增大的趋势.对于所选取的硬岩,采用13 mm刃宽滚刀破岩时比能最小,破岩效率最高;7 mm刃宽滚刀破岩时无法形成贯通岩片,相邻滚刀之间仍存在岩脊,破岩效率较低.

轻便式烟苗剪叶机的设计与试验

合理地对育苗期的烟苗进行剪叶,能增加烟苗移栽时的存活率和烟叶质量。现有的烟苗剪叶机以大中型机械为主,不适合西南地区常用的中棚漂浮育苗。为此,设计了一款轻便式自动调节烟苗剪叶机,以提高在西南地区中棚育苗棚内使用漂浮育苗技术时的剪叶效率,减少用人成本。该机主要结构包括圆盘刀片剪切装置和剪切高度调节装置,剪切高度调节装置能保证剪叶后的烟苗高度保持在同一水平面内。试验结果表明:剪叶完成后烟苗高度标准差为2.3 mm,烟苗漏剪率为1.64%,控制精度高,满足应用需求。

Cookie-Cutter集合的多重结构

给出Cookie-Cutter集合的一种新的多重分解,并计算其Hausdorff测度和Packing测度,得到了它们的Hausdorff维数和Packing维数。

KQL7/110矿用链臂切顶机在无煤柱煤矿开采技术中的研究与应用

随着煤矿开采工艺的不断进步,传统的切顶卸压无煤柱煤矿开采方法面临着安全风险高、操作复杂、效率低下等问题。为了解决这些问题,KQL7/110矿用链臂切顶机应运而生。该设备采用先进的链臂切割机构,能够实现对顶板的精准切割,有效解决了传统预裂爆破中常见的部分预裂孔未打通成缝问题,显著提高了切顶效果和顶板垮落的规整性,从而减少了后期巷道维护的难度。此外,KQL7/110链臂切顶机配备了智能化控制系统,实现了自动化操作,大幅降低了人工参与,提高了作业的安全性和效率。在实际应用中,KQL7/110矿用链臂切顶机在42204辅运巷的切顶泄压效果显著,实现了顶板沿切缝的完全垮落,极大地提高了切顶泄压效果。与传统爆破切顶方式相比,该设备显著降低了施工成本和巷道维护量,同时提高了矿井采煤回收率,延长了矿井的开采服务年限。通过收集大量试验数据,为设备性能优化和工艺改进提供了科学依据。KQL7/110矿用链臂切顶机的成功应用标志着煤矿切顶工艺向智能化、绿色化方向发展的重要一步。未来,煤矿开采工艺将继续向智能化方向发展,注重信息技术、自动控制技术和机器人技术的融合,以实现煤矿开采的自动化、信息化和智能化。这不仅可以提高生产效率和安全性,还可以有效减少环境污染,符合绿色发展的要求。

随机广义Cookie-cutter集上的随机紧测度的收敛性(英文)

首先构造了[0,T]上的随机广义cookie-cutter集KT.令Kn为构造KT中的第n级集合,并在Kn上定义记忆函数.基于这个记忆函数,定义了Kn上的随机概率测度φn(τ).令Ψn(.)=Eφn(.),其中Ψn为随机测度φn的紧测度.最后证明了序列Ψn是弱收敛的且有Ψ=limΨn.

广州地区复合地层大直径铁路隧道盾构选型及适应性分析

盾构法施工凭借效率高、扰动小等优势已然成为隧道工程建设中常用的手段。不同工程的地质水文环境不尽相同,盾构装备能否适应地质水文环境是决定施工能否高效、安全开展的关键因素,这在复合地层大直径隧道施工时更为明显。依托广州南站联络线隧道工程,识别出工程区间存在盾构选型适应性、刀盘刀具磨损、大直径浅埋盾构掘进控制三种重大风险,基于此针对盾构选型、刀盘刀具、推进驱动系统进行适应性选型设计。实践证明,经针对性设计后的盾构装备在此区间地层适应性优良,能够提升施工效率,保障施工安全。

关于“Cookie-Cutter集的性质”一个注

指出了专著"Techniques in Fractal Geometry"中关于Cookie-Cutter集的性质的一个小疏漏。

基于FEM-SPG耦合的盾构滚刀破岩仿真研究

隧道施工过程中岩石在盾构滚刀破岩力的作用下会发生破碎,传统的有限元方法(FEM)无法探究这一现象。为解决使用FEM面临网格畸变及无法同时分析岩石破碎的问题,引入光滑粒子伽辽金(SPG)分析方法,通过FEM和SPG耦合的方式建立了滚刀回转切削岩石模型。结果表明:FEM-SPG方法能够有效地展示岩石的密实核破碎过程及岩渣飞溅的现象。通过与CSM模型进行对比验证,发现仿真得到的滚刀垂直力与CSM模型相比误差为1.8%,验证了模型的可靠性。该方法与模型能够为滚刀精准破岩研究及分析岩石破碎机理提供新思路。

反吹式切焦器的开发和应用

焦炭塔顶部结焦问题是所有延迟焦化装置焦炭塔的痼疾。传统切焦器可将焦炭塔直筒部分的焦炭切除得较为干净,而切除顶部椭圆形封头处的焦炭时,则需解除除焦程序的联锁条件。随着钻杆高度的提升,联锁解除这样的操作方式对整个除焦系统和操作人员来说都是极为不安全的,而且也无法将顶部椭圆形封头处的焦炭彻底清理干净。针对上述问题,为保障操作人员和水力除焦设备的安全,某石化炼油厂焦化装置研发了反吹式切焦器。该设备自投用后,至今运行良好,为焦炭塔安全长周期生产提供了保障。文章介绍了该反吹式切焦器的组成、工作原理、设计计算方法和实际应用情况,希望能够为其他同类装置的清焦操作提供参考。

Rock deformation equations and application to the study on slantingly installed disc cutter

At present the mechanical model of the interac- tion between a disc cutter and rock mainly concerns indentation experiment, linear cutting experiment and tunnel boring machine （TBM） on-site data. This is not in line with the actual rock-breaking movement of the disc cutter and impedes to some extent the research on the rock-breaking mechanism, wear mechanism and design theory. Therefore, our study focuses on the interaction between the slantingly installed disc cutter and rock, developing a model in accordance with the actual rock-breaking movement. Displacement equations are established through an analysis of the velocity vector at the rock-breaking point of the disc cutter blade; the func- tional relationship between the displacement parameters at the rock-breaking point and its rectangular coordinates is established through an analysis of micro-displacement vectors at the rock-breaking point, thus leading to the geometric equations of rock deformation caused by the slantingly installed disc cutter. Considering the basically linear relationship between the cutting force of disc cutters and the rock deformation before and after the leap break of rock, we express the constitutive relations of rock deformation as generalized Hooke＇s law and analyze the effect of the slanting installa- tion angle of disc cutters on the rock-breaking force. This will, as we hope, make groundbreaking contributions to the development of the design theory and installation practice of TBM.

Fragmentation Energy-Saving Theory of Full Face Rock Tunnel Boring Machine Disc Cutters

Attempts to minimize energy consumption of a tunnel boring machine disc cutter during the process of fragmentation have largely focused on optimizing disc- cutter spacing, as determined by the minimum specific energy required for fragmentation; however, indentation tests showed that rock deforms plastically beneath the cutters. Equations for thrust were developed for both the traditional, popularly employed disc cutter and anew design based on three-dimensional theory. The respective energy consumption for penetration, rolling, and side-slip fragmentations were obtained. A change in disc-cutter fragmentation angles resulted in a change in the nature of the interaction between the cutter and rock, which lowered the specific energy of fragmentation. During actual field excavations to the same penetration length, the combined energy consumption for fragmentation using the newly designed cutters was 15% lower than that when using the traditional design. This paper presents a theory for energy saving in tunnel boring machines. Investigation results showed that the disc cutters designed using this theory were more durable than traditional designs, and effectively lowered the energy consumption.

有限-分层离散耦合方法滚刀回转切割力学特性模拟研究

全断面隧道掘进机(Tunnel Boring Machine,简称TBM)是一种具有高度自动机械化,集开挖、支护、出渣于一体的大型地下隧道施工设备。具有快速高效、安全可靠、机械化程度高、周围环境扰动小,适应性强等特点。TBM滚刀在刀盘上布置参数对破岩影响较大,因此采用有限差分软件和颗粒流离散元软件相结合,建立滚刀回转破岩模型,进行仿真模拟分析,深入研究了滚刀安装半径与三向力之间的关系,结果表明法向力与扭矩随着安装半径增大而增大,滚动力随着安装半径增加呈现出先增加后逐渐平稳,侧向力与安装半径之间不存在明显相关性。

Mechanical model of breaking rock and force characteristic of disc cutter

According to the cutting characteristics of progressive spiral movement by rotary cutting of the disc cutter, using the broken theory of interaction of compression and shearing, the three-axis force rotary cutting mechanical model of disc cutter was established and the influence of installation radius, the phase difference and the cutter space on the mechanics of disc cutter were analyzed. The results show that on the same radial line of tunneling interface, the boring distance of cutting tools installed on a different radius is not equal. The cutting radial line of tunneling interface is a polyline and its height is determined by phase angle and penetration of cutting tools. Both phase difference and the installation radius between adjacent disc cutters have little effect on the vertical force and rolling force, but increase with the increase in cutter spacing. In addition, when increasing phase difference and cutter space bilaterally, and reducing installation radius simultaneously, the lateral force would be improved. Related results have been verified onl O0 t rotary tool cutting test platform.

Design Theory of Full Face Rock Tunnel Boring Machine Transition Cutter Edge Angle and Its Application

At present, the inner cutters of a full face rock tunnel boring machine (TBM) and transition cutter edge angles are designed on the basis of indentation test or linear grooving test. The inner and outer edge angles of disc cutters are characterized as symmetric to each other with respect to the cutter edge plane. This design has some practical defects, such as severe eccentric wear and tipping, etc. In this paper, the current design theory of disc cutter edge angle is analyzed, and the characteristics of the rock-breaking movement of disc cutters are studied. The researching results show that the rotational motion of disc cutters with the cutterhead gives rise to the difference between the interactions of inner rock and outer rock with the contact area of disc cutters, with shearing and extrusion on the inner rock and attrition on the outer rock. The wear of disc cutters at the contact area is unbalanced, among which the wear in the largest normal stress area is most apparent. Therefore, a three-dimensional model theory of rock breaking and an edge angle design theory of transition disc cutter are proposed to overcome the flaws of the currently used TBM cutter heads, such as short life span, camber wearing, tipping. And a corresponding equation is established. With reference to a specific construction case, the edge angle of the transition disc cutter has been designed based on the theory. The application of TBM in some practical project proves that the theory has obvious advantages in enhancing disc cutter life, decreasing replacement frequency, and making economic benefits. The proposed research provides a theoretical basis for the design of TBM three-dimensional disc cutters whose rock-breaking operation time can be effectively increased.

Prediction of Dynamic Cutting Force and Regenerative Chatter Stability in Inserted Cutters Milling

Currently, the modeling of cutting process mainly focuses on two aspects: one is the setup of the universal cutting force model that can be adapted to a broader cutting condition; the other is the setup of the exact cutting force model that can accurately reflect a true cutting process. However, there is little research on the prediction of chatter stablity in milling. Based on the generalized mathematical model of inserted cutters introduced by ENGIN, an improved geometrical, mechanical and dynamic model for the vast variety of inserted cutters widely used in engineering applications is presented, in which the average directional cutting force coefficients are obtained by means of a numerical approach, thus leading to an analytical determination of stability lobes diagram (SLD) on the axial depth of cut. A new kind of SLD on the radial depth of cut is also created to satisfy the special requirement of inserted cutter milling. The corresponding algorithms used for predicting cutting forces, vibrations, dimensional surface finish and stability lobes in inserted cutter milling under different cutting conditions are put forward. Thereafter, a dynamic simulation module of inserted cutter milling is implemented by using hybrid program of Matlab with Visual Basic. Verification tests are conducted on a vertical machine center for Aluminum alloy LC4 by using two different types of inserted cutters, and the effectiveness of the model and the algorithm is verified by the good agreement of simulation result with that of cutting tests under different cutting conditions. The proposed model can predict the cutting process accurately under a variety of cutting conditions, and a high efficient and chatter-free milling operation can be achieved by a cutting condition optimization in industry applications.

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 from5621 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.

Wear Analysis of Disc Cutters of Full Face Rock Tunnel Boring Machine

Wear is a major factor of disc cutters’ failure. No current theory offers a standard for the prediction of disc cutter wear yet. In the field the wear prediction method commonly used is based on the excavation length of tunnel boring machine（TBM） to predict the disc cutter wear and its wear law, considering the location number of each disc cutter on the cutterhead（radius for installation）; in theory, there is a prediction method of using arc wear coefficient. However, the preceding two methods have their own errors, with their accuracy being 40% or so and largely relying on the technicians’ experience. Therefore, radial wear coefficient, axial wear coefficient and trajectory wear coefficient are defined on the basis of the operating characteristics of TBM. With reference to the installation and characteristics of disc cutters, those coefficients are modified according to penetration, which gives rise to the presentation of comprehensive axial wear coefficient, comprehensive radial wear coefficient and comprehensive trajectory wear coefficient. Calculation and determination of wear coefficients are made with consideration of data from a segment of TBM project（excavation length 173 m）. The resulting wear coefficient values, after modification, are adopted to predict the disc cutter wear in the follow-up segment of the TBM project（excavation length of 5621 m）. The prediction results show that the disc cutter wear predicted with comprehensive radial wear coefficient and comprehensive trajectory wear coefficient are not only accurate（accuracy 16.12%） but also highly congruous, whereas there is a larger deviation in the prediction with comprehensive axial wear coefficient（accuracy 41%, which is in agreement with the prediction of disc cutters’ life in the field）. This paper puts forth a new method concerning prediction of life span and wear of TBM disc cutters as well as timing for replacing disc cutters.

Endoscopic submucosal dissection for esophageal granular cell tumor using the clutch cutter

Endoscopic submucosal dissection (ESD) with a knife is a technically demanding procedure associated with a high complication rate.The shortcomings of this method are the deficiencies of fixing the knife to the target lesion,and of compressing it.These shortcomings can lead to major complications such as perforation and bleeding.To reduce the risk of complications related to ESD,we developed a new grasping type scissors forceps (Clutch Cutter,Fujifilm,Japan) which can grasp and incise the targeted tissue using an electrosurgical current.Esophagogastroduodenoscopy on a 59-year-old Japanese man revealed a 16mm esophageal submucosal nodule with central depression.Endoscopic ultrasonography demonstrated a hypoechoic solid tumor limited to the submucosa without lymph node involvement.The histologic diagnosis of the specimen obtained by biopsy was granular cell tumor.It was safely and accurately resected without unexpected incision by ESD using the CC.No delayed hemorrhage or perforation occurred.Histological examination confirmed that the granular cell tumor was completely excised with negative resection margin.We report herein a case of esophageal granular cell tumor successfully treated by an ESD technique using the CC.