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。     

TBM滚刀贯入度及受力影响研究

掘进机(TBM)刀盘滚刀间距布置是否合理关系着其破岩速率的高低。为了探究滚刀间距对TBM破岩的影响,文章采用离散元软件PFC~(3D)模拟滚刀的线性切割实验,对不同贯入度的滚刀破岩效果进行研究。研究结果表明:(1)随着贯入度增大,平均滚动力和平均侧向力逐渐增大;后滚刀的平均滚动力和平均侧向力略大于前滚刀。(2)随贯入度增大,前滚刀平均垂直力逐渐增大。贯入度为4 mm时,岩石未产生贯穿裂缝,形成岩脊,后滚刀平均垂直力小于前滚刀;贯入度为6 mm时,裂缝分布较密且扩展连接形成贯通裂缝,后滚刀平均垂直力相对前滚刀降低10%;贯入度为8 mm时,裂缝贯通且岩石过度破碎,后滚刀平均垂直力相对于前滚刀大幅度降低,降低幅值达51%。     

线性和旋转切割方式滚刀破岩试验对比研究

隧道掘进机(TBM)的施工中破岩效率直接影响了工程的进度、造价。室内试验可以较真实地模拟滚刀破岩的过程,优化TBM设计参数。由于试验设备的限制,此前室内试验均为线性切割,与实际施工的旋转滚刀旋转破岩有一定差异。基于北京工业大学自主研制的机械破岩试验平台,采用19in(483mm)常截面盘形滚刀,以80mm刀间距、0.5mm贯入度为间隔,分别对某引水工程花岗岩进行线性切割和旋转切割破岩试验。对比分析了两种切割方式对滚刀力、比能的影响,发现两种切割方式下法向力、滚动力和比能变化趋势大体相同,只有侧向力存在明显差异。     

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。     

复合地层TBM滚刀破岩性能离散元数值试验

全断面岩石掘进机(TBM)因其安全性好、掘进速度快、机械化程度高等优点,已被引入煤矿岩石巷道掘进施工中。煤矿地质条件复杂,复合地层对全断面岩石掘进机掘进效率的影响不容忽视。为了探究煤系复合地层对滚刀破岩效率的影响,建立了滚刀和岩石的颗粒流离散单元模型,开展TBM滚刀的贯入度数值实验。研究结果表明:在相同破岩情况下复合地层破坏的范围小,在滚刀破岩的过程中不易形成贯通区。两种地层裂纹数目随着贯入度变化的规律大致相同。滚刀在相同破岩情况下复合地层所需要的滚刀法向力要大于单一地层硬岩所需要的。单一地层滚刀破岩最优贯入度约为4mm,复合地层滚刀破岩最优贯入度约为9mm。     

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。     

常截面滚刀贯入试验中岩石破坏行为分析

为研究滚刀贯入过程中不同强度岩石的破坏行为,采用泥岩、花岗岩、砂岩和水泥砂浆制作立方体试样,结合岩石贯入试验加载系统和声发射监测系统,进行无侧向约束条件和有侧向约束条件下TBM常截面盘形滚刀贯入试验,获得完整荷载–贯入度曲线和声发射参数信息,分析不同岩石试样的破坏过程、破坏类型和破坏模式。结果表明:(1)软岩试样荷载–贯入度曲线跌落现象不明显,呈现延性破坏特征,而硬岩试样荷载–贯入度曲线跌落现象显著,具有脆性断裂特征。(2)无侧向约束条件下试样破坏类型属于劈裂破坏模式,有侧向约束条件下试样破坏过程由中间劈裂裂纹和侧向裂纹共同控制。(3)声发射参数曲线和荷载–贯入度曲线之间具有良好的对应关系,可以反映贯入过程中岩石试样内部损伤劣化和宏观裂纹形成过程。(4)类岩石材料滚刀贯入试验在一定程度上有助于更好地理解岩石贯入破坏过程和破坏模式,但类岩石材料与自然岩石材料在强度和变形性质上并不能完全吻合,因此相似材料模拟试验的结果需要进一步的验证。     

贯入度与刀间距对TBM滚刀破岩推力的影响

针对目前盾构机在硬岩地层施工中经常遇到刀具选型、掘进速度慢及参数设定不确定等难题,本文以施工现场高硬度凝灰岩为岩样,进行了推力与贯入度和刀间距与破岩推力的试验。研究盾构两种常规滚刀的刀间距、掘进转速及贯入度的关系,为类似硬岩盾构施工提供试验基础和参考。     

复合地层盾构掘进滚刀荷载试验研究

为了探究复合地层盾构掘进时滚刀的荷载与开挖面岩石强度、切削速度、刀圈贯入度之间的关系以及滚刀在不同地层界面处的受力特征,开展了复合地层盾构滚刀掘进试验,采用原型滚刀分工况对多种材料组成的开挖面模型进行掘进试验,同时采集滚刀的荷载数据。研究结果表明：滚刀在依次切削粉质黏土、M2.5水泥砂浆、C15混凝土与C30混凝土时的荷载整体上呈阶梯上升的趋势,并始终处于波动状态;滚刀的荷载会随刀间距的增大有一定程度的增大,但增幅较小;滚刀在切削不同材料时的荷载随刀圈贯入度的增大呈近似的线性增大趋势,当切削脆性材料时该规律尤为明显;较大的材料刚度和滚刀贯入度使得被切材料发生更大的弹性变形,从而使得滚刀对材料做功以及材料破碎时的能量释放量都较大,造成滚刀荷载的波动幅度也有一定程度的增大;当刀盘转速增大时,滚刀荷载也呈增大趋势,增大幅度会随着刀盘转速的增大逐渐趋缓,其原因是切削速率的增大造成被切材料动态强度增大。     

引洮工程9号隧洞TBM滚刀磨损原因分析

对引洮供水工程9号隧洞TBM滚刀的磨损原因进行了分析,认为不完全胶结的砂岩和TBM刀盘开口率低是导致滚刀刀圈磨损成针尖状的主要原因,并据此提出了防止滚刀磨损的3项建议:加宽滚刀刀刃宽度,将滚刀刀刃设计为平角;增加刀盘的开口率;根据围岩变化情况控制滚刀的贯入度在合理的范围内。     

Prediction of thrust and torque requirements of TBMs with fuzzy logic models

For successful tunnel excavations, selection of proper tunnel boring machine (TBM), optimization of design parameters and prediction of their performance are critical. Normal and rolling forces of disc cutters are used for determination of thrust, torque and power requirement of TBMs as well as prediction of their performance. Much research has been conducted to predict these parameters of disc cutters using analytical, empirical and numerical approaches. In recent years alternative methods, such as fuzzy logic, have been extensively used to deal with subjects having ambiguities and uncertainties. A model was established to predict normal forces of constant cross section (CCS) disc cutters in the rock cutting process by using fuzzy logic method. The other model which predicts specific energy requirement of disc cutter can also be used for predicting the rolling forces of these cutters. These models are based on experience and verified the database which consists of linear cutting test results generated at the Earth Mechanics Institute of the Colorado School of Mines. The models predict forces of disc cutters using uniaxial compressive and tensile strength of rocks, disc diameter and tip width, penetration and spacing of cuts.     

Disc cutting tests in Colorado Red Granite: Implications for TBM performance prediction

A series of full-scale laboratory disc cutting tests was conducted with a single disc cutter (432 mm diameter and a constant cross-section profile) and a single rock type (a coarse-grained red granite). Normal, rolling, and side forces were measured for a series of spacings and penetrations, from which other cutting parameters also were calculated. Although the increases of normal and rolling forces with increased spacing and penetration are as expected, the results illuminate additional aspects of performance prediction. Specific energy (SE) considerations indicate that a spacing of 76 mm is close to optimum in this hard, brittle crystalline rock. At this spacing, penetration has very little effect on SE. These results show why spacings near 76 mm are commonly found on tunnel boring machines operating in hard rock. The relationship of rolling force to normal force was close and consistent: A nearly linear rise of the ratio of rolling force to normal force with increased penetration, and, conversely, a nearly unchanged ratio with increases in spacing. The results tend to validate performance prediction methodologies based on normal force-penetration models.     

基于协同破岩的TBM刀盘优化策略

岩石隧道掘进机工作时的刀具受力情况是影响刀盘破岩性能的关键。为了分析滚刀之间的协同破岩效应,提出3种基本的协同破岩模式,并将多把滚刀协同破岩过程等效为3种破岩模式的组合。不同破岩模式下,滚刀切割岩石的先后顺序不同,结合线性切割试验,证实了不同模式下3种滚刀力等级的大小关系。以引汉济渭岭北隧洞TBM工程为背景,研究得出名义磨损量与破岩模式的叠加效应具有较强的相关性,其中,由内而外模式占比与滚刀名义磨损量具有明显的正相关性,据此提出了考虑刀具磨损量的TBM刀盘刀具优化策略。     

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.     

Study on the influence of joint spacing on rock fragmentation under TBM cutter by linear cutting test

Joint spacing is one of the most important geological factors influencing rock fragmentation by TBM cutters and TBM performance. In order to study the influence of joint spacing, full-scale linear cutting tests have been conducted for the Beishan granite samples with different joint spacing (i.e. one intact sample, two jointed samples with joint spacing of 100 mm and 400 mm). For different joint spacing, the influence of penetration depth on rock fragmentation was also explored by varying the penetration depth with an interval of 0.5 mm. During the test process, the three directional forces acting on the TBM cutter were recorded, and the rock chips formed by each cutting pass were weighed, respectively. By analysing the cutting force, crack initiation/propagation and rock chips, the influences of joint spacing on rock fragmentation process by TBM cutter were investigated. The test results showed that the increase of penetration depth cannot improve the TBM breakage efficiency after reaching a certain value for the intact rock sample, and the normal force for intruding the intact rock is larger than that for intruding the rock jointed samples. It is also found that the sample part below the joint plane is intact, thus joint can restrain the crack propagating cross the joint plane and facilitates the chips formation on the cutting surface. For the rock sample with joint spacing of 100 mm, two rock fragmentation modes were found during the cutting process. One mode is that the cracks initiate from the crushed zone under TBM cutter, and the cracks propagate to the joint plane, consequently form large rock chips. The other one is that the cracks initiate from the joint plane and then propagate to the rock cutting surface, and the cracks initiate before the formation of the crushed zone under the cutter. For the rock sample with joint spacing of 400 mm, there are two rock fragmentation stages, i.e., the normal rock fragmentation stage and the joint-controlled rock fragmentation stage. There is a transitional process between these two stages, and also the median crack can be promoted to propagate vertically to joint plane due to the joint existence. This study can provide useful guidance for operation optimization and performance prediction for TBM operating in jointed rock masses.     

高地应力作用下大理岩岩体的TBM掘进试验研究

滚刀破岩效率的研究主要集中在室内线性试验机破岩试验和数值分析2个方面,在工地开展TBM掘进试验尚不普遍。锦屏二级水电站采用3台TBM开挖隧道群,3台TBM在不同洞深(不同地应力)条件对大理岩岩体进行TBM掘进试验、岩石渣片筛分试验及大渣片统计分析,研究岩体条件、TBM机器参数、TBM运行参数对TBM掘进速度的影响及高地应力作用下岩体可掘性指数的变化。研究结果表明:在高地应力条件下,尽管TBM掘进速度随推力增加而增大,但推力超过一定值后,TBM并不在优化状态下运行,TBM的运行需与岩体条件及地应力条件相匹配。     

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。     

岩石隧道掘进机的施工预测模型

分析了岩石隧道掘进机的破岩机理,介绍了自上世纪70年代以来发展的一系列施工预测模型,包括单因素预测模型、综合预测模型(CSM模型和NTNU模型)、岩体分类预测模型(QTBM模型)、概率模型、模糊神经网络模型。单因素预测模型中包括的主要岩石材料参数有岩石单轴抗压强度、抗拉强度及岩石的总硬度;CSM模型主要是基于线性切割试验机岩石试验数据,其初始预测模型中包括岩石单轴抗压强度及抗拉强度;NTNU模型是一套完整的预测模型,包括掘进速度、进度预测、刀具的磨损预测及经济分析,在它的施工进度预测模型中,考虑到了岩石的可钻性、孔隙度及岩体节理的密度及方向;QTBM模型源自于Q系统,加入了一些与隧道掘进机及与掘进速度相关的参数;概率模型是基于一个庞大数据库的类比模拟模型;模糊神经网络模型是一种黑箱模型,克服了输入与输出之间的不确定性关系。