Rock fragmentation under different installation polar angles of TBM disc cutters

The disc cutters of tunnel boring machine(TBM) are installed with different polar angles. This causes the cutting depth difference between adjacent disc cutters on the tunnel face. A rock-cutting model was established to study the rock fragmentation law between adjacent disc cutters with different polar angles based on particle flow code(PFC). The influence of polar angle of adjacent disc cutters on rock cracks and stresses under different cutter spacing and penetration was studied. Research shows that polar angle difference leads to the discontinuity of rock-fragmentation process by adjacent cutters. The effect of rock-fragmentation is influenced by the cutting depth difference between adjacent cutters. The effect of rock-fragmentation performed best, meanwhile large rock blocks were flaked when the difference of cutting depth is half of the penetration. Too large or small difference of the cutting depth will cause high specific energy consumption of rock fragmentation. The specific energy consumption is relatively small when the difference of cutting depth is half of the penetration.

Differentiation and analysis on rock breaking characteristics of TBM disc cutter at different rock temperatures

In order to study rock breaking characteristics of tunnel boring machine(TBM) disc cutter at different rock temperatures,thermodynamic rock breaking mathematical model of TBM disc cutter was established on the basis of rock temperature change by using particle flow code theory and the influence law of interaction mechanism between disc cutter and rock was also numerically simulated.Furthermore,by using the linear cutting experiment platform,rock breaking process of TBM disc cutter at different rock temperatures was well verified by the experiments.Finally,rock breaking characteristics of TBM disc cutter were differentiated and analyzed from microscale perspective.The results indicate the follows.1) When rock temperature increases,the mechanical properties of rock such as hardness,and strength,were greatly reduced,simultaneously the microcracks rapidly grow with the cracks number increasing,which leads to rock breaking load decreasing and improves rock breaking efficiency for TBM disc cutter.2) The higher the rock temperature,the lower the rock internal stress.The stress distribution rules coincide with the Buzin Neske stress circle rules: the maximum stress value is below the cutting edge region and then gradually decreases radiant around; stress distribution is symmetrical and the total stress of rock becomes smaller.3) The higher the rock temperature is,the more the numbers of micro,tensile and shear cracks produced are by rock as well as the easier the rock intrusion,along with shear failure mode mainly showing.4) With rock temperature increasing,the resistance intrusive coefficients of rock and intrusion power decrease obviously,so the specific energy consumption that TBM disc cutter achieves leaping broken also decreases subsequently.5) The acoustic emission frequency remarkably increases along with the temperature increasing,which improves the rock breaking efficiency.

The three-dimension model for the rock-breaking mechanism of disc cutter andanalysis of rock-breaking forces

To study the rock deformation with three- dimensional model under rolling forces of disc cutter, by car- rying out the circular-grooving test with disc cutter rolling around on the rock, the rock mechanical behavior under rolling disc cutter is studied, the mechanical model of disc cutter rolling around the groove is established, and the the- ory of single-point and double-angle variables is proposed. Based on this theory, the physics equations and geometric equations of rock mechanical behavior under disc cutters of tunnel boring machine （TBM） are studied, and then the bal- ance equations of interactive forces between disc cutter and rock are established. Accordingly, formulas about normal force, rolling force and side force of a disc cutter are de- rived, and their validity is studied by tests. Therefore, a new method and theory is proposed to study rock- breaking mech- anism of disc cutters.

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.

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.

考虑岩石细观结构的TBM滚刀破岩过程数值研究

为研究TBM滚刀的破岩机制,基于颗粒离散元方法与Voronoi元素,采用平行黏结接触模型与平节理接触模型,提出具有岩石细观结构特征的改进等效晶质模型,实现对TBM滚刀破岩过程的模拟。通过室内试验与数值模拟计算结果的对比分析,验证该改进等效晶质模型在滚刀破岩研究中的适宜性和可靠性。研究结果表明:滚刀破岩过程可分为4个阶段,即线性加载阶段、屈服硬化加载阶段、卸载阶段和残余跃进阶段;晶间张拉裂纹在总裂纹数中占主导地位,晶内裂纹是引起宏观裂纹产生的重要原因;随晶体平均粒径增加,岩石破碎程度与峰值破岩荷载均增大;随滚刀刀圈宽度增大,裂纹总数与晶内裂纹所占比例均增加,破岩峰值应力与破岩体积也增大。研究结果可为TBM滚刀刀头配置提供参考依据。

TBM掌子面力学模型与滚刀破岩力推力预测

以掌子面岩体破坏前状态建立了滚刀推力作用的双集中力模型,采用弹性半空间理论的Boussinesq解答和叠加原理,给出了双滚刀协同作用下岩体应力分布的解析解。根据应力分布的特点和TBM破岩要求,提出了TBM破岩的必要条件;采用单轴强度理论和多轴强度理论,分别给出了滚刀破岩推力的预测公式。工程实例表明,采用本文提出的基于多轴强度理论的预测公式计算出的滚刀破岩推力与TBM工作时实际使用的推力非常吻合。

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.

TBM滚刀贯入度对破岩效能的影响规律研究

合理设置TBM贯入度参数对于特定地质条件下的掘进效率至关重要。为研究TBM盘型滚刀在不同贯入度下的破岩效果,采用自主研发的滚刀破岩缩尺试验平台,在不同边界条件下对花岗岩开展盘型滚刀线性切割试验,通过使用FEM(finite element method)和SPH(smooth particle hydrodynamics)相耦合的数值模拟方法重现相关试验以验证模型的合理性,并在此基础上建立原尺双滚刀回旋破岩三维数值模型,研究TBM盘型滚刀不同贯入度下对花岗岩的破岩效果。研究结果表明:有侧限条件下滚刀受力和岩碴体积往往更大,且相邻贯入度之间的法向力和岩碴体积增长幅度随着贯入度的增大而减小,但无侧限条件下的破岩效率更高;滚刀破岩过程是阶跃性的,岩碴的产生主要集中在滚刀荷载跌落阶段,无论刀侧是否存在限制,刀下岩石均被碾压至极细的粉末,刀侧岩石崩出,且岩碴的大小与滚刀荷载跌落幅度正相关;刀下岩石破坏区域近似呈“V”形,随着贯入度的增大,滚刀间的“V”形破坏区域持续向安装半径内侧倾斜;滚刀破岩效率随着贯入度的增大先提高后减小,针对试验岩样,最佳贯入度为2~4mm;本研究所采用滚刀破岩缩尺试验与FEM-SPH数值模拟相结合的方法可以很好地重现花岗岩破裂过程,且两者切削力相对误差均在10%以内,可以为后续TBM滚刀破岩研究提供一定参考。

基于脉冲涡流的TBM盘形滚刀磨损检测方法

为保障TBM高效安全运行,提出一种脉冲涡流检测(PECT)的刀圈径向磨损量无损检测方法。先基于Maxwell时变电磁场理论建立有限元模型,采用控制变量法探究线圈高度、内半径和外半径3个激励线圈参数的优化策略;再搭建刀圈径向梯度化磨损量无损检测有限元模型,研究刀圈径向磨损量与前期电压信号积分值的映射关系,提取可连续反映刀圈磨损程度的特征量,并研究不同提离距离下刀圈径向磨损量与特征量的映射关系。结果表明:在给定激励线圈外半径取值的前提下合理调节内半径取值,可最大程度兼顾对激励线圈高分辨率、强耦合程度的要求;检测线圈与刀圈的最远距离为64 mm,在满足48.26 cm刀圈最大径向磨损量为35 mm的基础上保留了29 mm余量,比传统涡流检测的最远提离距离提高了83%;该方法提高了探头远距离检测能力,保障了探头安装空间,同时显著降低了探头被岩碴刮擦损伤的风险。

高应力条件下TBM破岩岩渣块度分布规律研究

TBM掘进过程产生的岩石渣料包含丰富的地质信息,为研究地应力对TBM掘进过程产生的岩石渣料的影响,采用PFC2D建立了围压条件下的滚刀破岩模型,提取并分析破岩产生的岩石碎片。数值模拟结果表明:TBM滚刀掘进过程主要产生扁平形岩石碎片。在一定范围内,随着围压增加,岩石碎片的平均粒径呈“W”形变化,并且小粒径碎片的含量增加,但围压较高(>30 MPa)时,反而更容易形成较大粒径的岩石碎片。

高压水射流前方切缝辅助TBM滚刀破岩试验研究

为提升坚硬岩层TBM滚刀破岩效率,降低滚刀磨损及消耗进而提高TBM整机掘进速度,采用最新研制的高压水射流辅助TBM滚刀破岩试验测试系统,进行坚硬花岗岩水射流先行切割滚刀后行破岩的室内试验,研究同一掌子面相同切深、不同刀间距条件下全尺度滚刀的受力规律和破岩特征。结果表明,完整岩石及水射流作用下滚刀的法向力、滚动力和侧向力随刀间距的增加缓慢增加;相比完整岩石,三向力降低幅度分别为19%~41%、10%~34%和16%~59%,破岩体积增加24%~72%,破岩比能降低7%~48%,切割系数升高幅度为6%~17%,且随着刀间距的增加缓慢降低;水射流切缝岩石碎片的尺寸明显增大,但岩粉质量有所降低,岩石破坏多数以张拉破坏为主。

基于新表面理论的TBM破岩效率评价指标

岩碴是岩-机作用的直接产物,也是评价隧道掘进机(TBM)破岩效率和优化TBM掘进参数的有效指标。依托兰州水源地建设工程和龙岩万安溪引水工程,开展不同岩性条件下TBM岩碴筛分试验,得到了岩碴粒径分布规律。基于新表面理论,从滚刀破岩能量转化角度出发,提出了一种新的TBM破岩效率评价指标。基于岩碴粒径分布规律和TBM掘进参数统计,探讨了新表面理论指标与比能、岩碴粗糙度指数之间的关系,指出了新表面理论指标在反映岩碴破碎程度和评价TBM破岩效率方面的优势。对新表面理论指标与TBM掘进推力以及刀间距s与贯入度p的比值进行回归分析,得到了硬岩(围岩等级为Ⅱ级)和软岩(围岩等级为III级)掘进条件下的TBM最优掘进推力和s/p取值区间。研究表明:(1)新表面理论指标符合岩石破碎学原理,可准确评价TBM破岩效率。岩碴越是破碎,新表面理论指标越大,掘进能耗越高,此时TBM破岩效率相对较低。(2)新表面理论指标与比能、岩碴粗糙度指数均具有良好的线性相关关系。岩碴越是破碎,破碎单位体积岩石的能量消耗越大,新表面理论指标越大,对应的粗糙度指数越小。软岩掘进条件下TBM掘进比能低于硬岩,而岩碴破碎程度高于硬岩。(3)新表面理论指标随着TBM掘进推力和s/p的增加先减小后增大,在硬岩和软岩条件下,当TBM最优掘进推力区间和s/p区间分别为7 400~7 700 kN、13.9~14.4和1 000~1 500 kN、8.0~8.5时,新表面理论指标较小,TBM破岩效率较高。

倾斜临空面下隧道掘进机滚刀贯入破岩研究

在临空面辅助隧道掘进机(tunnel boring machine,简称TBM)滚刀破岩的过程中,当滚刀在垂直临空面附近完成破岩后,垂直临空面将变为倾斜临空面。为了研究倾斜临空面对滚刀贯入破岩的影响,利用近场动力学方法建立了三维模型,考虑了临空面倾斜程度以及滚刀临空距离的变化,开展了一系列数值研究。模拟结果表明,在倾斜临空面辅助TBM滚刀贯入破岩工况下,岩石存在两种破碎模式,一种为内部裂纹扩展模式,另一种为内部压碎区扩大模式。在滚刀临空距离固定为40 mm的情况下,随着临空面倾角θ余切值cotθ的增加,岩石破碎逐渐从内部裂纹扩展模式转变为内部压碎区扩大模式,滚刀的法向峰值力与破岩消耗能量也逐渐增大,而且内部压碎区扩大模式的破岩效率比内部裂纹扩展模式低。随着滚刀临空距离的增加,滚刀法向峰值力、破岩消耗能量与破岩体积逐渐增加,同时滚刀的破岩效率也得到了提升。

TBM滚刀破岩动态特性与最优刀间距研究

在对实际工况合理简化的基础上,从岩土细观角度出发,采用颗粒离散元法建立滚刀侵入岩体的二维模拟模型,研究双滚刀作用下岩体的动态响应机制,找出滚刀侵入过程中岩体裂纹、贯入度以及切削力三者的关系。在此基础上,通过数值模拟对常见切深下滚刀最优刀间距问题进行分析,得到不同切深下比能耗与刀间距的规律,并通过试验对双滚刀破岩过程中岩体动态特性以及最优刀间距问题进行验证,最后以工程实例验证研究结论。研究表明:仿真过程中,切削力随贯入度的变化与岩体的跃进破碎特性相一致,岩体破坏服从格里菲斯理论;较小切深下岩体为剪切破坏,较大切深下岩体发生拉应力破坏;切深为10 mm时比能耗有明显拐点,此时刀间距为100 mm;切深为6 mm时,60 mm刀间距下比能耗最小;切深小于2 mm时,实际工况下岩体不能产生贯穿裂纹。

TBM滚刀破岩过程影响因素数值模拟研究

全断面岩石掘进机(TBM)的破岩效率主要受刀盘设计和岩体特征的影响。采用颗粒流方法建立了岩石试件与滚刀的数值模型,对TBM滚刀破岩过程的影响因素进行了分析。研究表明,单刃滚刀交替作用下强度较低的岩石中易形成规则的张拉裂纹而生成较大岩碴;强度较高的岩石中滚刀的侧向挤压促使形成块度较小的片状岩碴;双刃滚刀作用下岩石表面受到强烈挤压后出现较大的拉应力,使岩石更易破碎,且仅在强度较高的岩石中才易形成透镜状岩碴。滚刀破岩过程中存在能耗最小的最佳间距,该最佳间距随着岩石强度的增大而减小。滚刀破岩过程中,结构面对裂纹扩展具有显著的控制性作用,并阻隔损伤向结构面下的岩石中渗透;随着结构面与滚刀侵入方向夹角的减小,结构面将引导裂纹向岩石深部扩展,而当夹角较大时,结构面则会引导裂纹横向扩展,易导致大块岩碴的形成。

TBM边缘滚刀破岩机理的数值研究

为研究刀刃角和不同被切削材料对全断面硬岩掘进机(TBM)边缘滚刀破岩机理的影响规律,基于二维离散单元法,利用UDEC仿真软件建立了一系列边缘滚刀破岩数值模型,对边缘滚刀作用下被切削体内部裂纹生成、扩展和破碎过程进行数值模拟。仿真结果表明:张拉破坏是滚刀破岩时裂纹生成与扩展的主要原因;对于不同刀刃角的边缘滚刀接近弧面下端的斜裂纹长度要比弧面上端的长;大理岩裂纹扩展能力和破岩效率均随刀刃角的增大先增大后减小,因此对于硬岩刀刃角不宜过小也不宜过大;随着被切削材料强度增大,裂纹扩展越不充分,裂纹扩展能力和破岩效率均降低;与其他材料相比,TBM边缘滚刀对大理岩破坏损伤范围最小,破岩效率最低。最后通过实验和工程数据验证了仿真方法的正确性和可行性。

基于颗粒流模型的TBM滚刀破岩过程数值模拟研究

为了研究全断面岩石掘进机(TBM)盘型滚刀的破岩机制及其影响因素,采用颗粒流方法建立了岩石与滚刀的二维数值模型,实现了对TBM滚刀破岩过程的模拟。分析表明,滚刀的破岩过程可分为冲击挤压破碎、大量微裂纹生成、张拉性主裂纹扩展3个阶段,证实了滚刀破岩的挤压-张拉破坏理论。在滚刀侵入深度相同的前提下,随着刀圈刃角以及刃宽的增加,滚刀下的压碎区也相应增大,张拉性主裂纹数目增多,滚刀的破岩能力提高;与平刃刀圈相比,楔刃刀圈的"楔块劈裂"作用更加显著,使径向裂纹扩展得更快且更深入岩石内部。TBM滚刀对强度较高或较低岩石的破坏损伤较小,而对中等强度的岩石破坏损伤最为显著。

不同模式下TBM刀群三维回转切削仿真与优化设计

针对TBM刀群回转切削问题,建立了17寸盘形滚刀刀群切削岩石的数值仿真模型,使用有限元仿真分析软件ANSYS LS-DYNA对不同工作模式下的盘形滚刀回转切削岩石工作过程进行仿真。仿真结果表明,通过对盘形滚刀刀间距进行优化设计,分析不同刀间距下滚刀的力学参数,得到在该地质条件下,中心滚刀最优刀间距为75 mm、正滚刀最优刀间距为80 mm;通过对边滚刀安装角度进行优化,分析不同安装角度下滚刀的力学参数,得到边滚刀最优安装角度为6.5°;通过对滚刀切削岩石的顺次切削角度进行优化,分析不同顺次切削角度下滚刀的力学参数,得到正滚刀最优顺次切削角度为30°、边滚刀为20°。

节理特征对TBM盘形滚刀破岩特性的影响

为了研究节理特征对全断面岩石掘进机(TBM)盘形滚刀破岩机制的影响,从岩体细观尺度出发,基于颗粒离散元法建立不同节理强度、间距和倾角特征下盘形滚刀破碎中分化灰岩的数值模型,模拟TBM滚刀切削岩石时岩石裂纹生成、扩展和碎块形成的全过程,以及滚刀受力和岩石应力分布状态。研究结果表明:岩体中的节理面能改变裂纹扩展方式,阻隔损伤向节理面下的岩石传播,且低强度节理面阻隔损伤的能力较强;节理间距对岩碴的块状大小有较大影响,当节理间距减小时破岩效率升高;节理岩体存在3种基本的破碎模式,主要与节理倾角有关;当节理倾角为60°时,破岩比能耗最小,滚刀破岩效率达到最高值。