围压对 TBM 滚刀破岩影响机制研究

穿越高大山体的隧道TBM施工不可避免地会遇到高地应力问题,研究地应力对TBM滚刀破岩机制和掘进效率的影响具有重大的工程价值和科学意义。通过理论分析和UDEC数值模拟技术对围压作用下滚刀破岩模式进行研究,发现围压对滚刀破岩过程影响比较复杂:围压对粉碎区深度和裂纹扩展区内滚刀作用方向的裂纹扩展起到抑制作用;而对围压作用方向的裂纹扩展有促进作用,表现为边裂纹的扩展范围会更大,扩展路径会更加平直,发展更加迅速,滚刀间岩片的形成更加容易。TBM现场掘进试验表明,地应力越高,围压作用越明显,TBM破岩更加容易,掘进效率会更高。从TBM滚刀作用下岩片形成的难易程度角度考虑,理论分析、数值模拟和TBM现场掘进试验都表明围压作用促进TBM滚刀破岩。     

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。     

围压对TBM滚刀破岩影响的数值模拟研究

采用一种新的无网格数值计算方法—广义粒子动力学法(GPD),研究了水平方向围压为0,5,10,15,20 MPa条件下,全断面隧道掘进机(TBM)滚刀的破岩过程及破岩模式,分析了围压对岩体可掘性的影响。得到:(1)围压的存在抑制中央裂纹的扩展;(2)随着围压的增加,赫兹裂纹的扩展方向发生偏转,与水平面的夹角变小;(3)相同贯入度下,随着围压的增加,滚刀法向力及其掘进指数均增加。利用GPD法分析了锦屏二级水电站隧道施工中,含节理的岩层中高地应力对TBM滚刀破岩的影响,成功模拟出高地应力下节理岩体的板裂化现象,得到高地应力能够使岩体产生板裂化促进滚刀破岩。     

复合岩层中TBM滚刀与围岩相互作用机理的数值模拟研究

为提高硬岩隧道掘进机(tunnel boring machine,TBM)在复合岩层的掘进效率,采用PFC2D(particle flow code 2D)探讨了不同围压下复合岩层裂纹扩展机制,同时采用定量的方法揭示了滚刀间距、贯入度及岩层倾角对破岩效率的影响。结果表明:1)滚刀同软岩直接接触时,滚刀下部裂纹较多,而消耗的能量较少。相反,滚刀同硬岩直接接触时,滚刀下部裂纹较少,消耗的能量却较多。2)岩层倾角对破岩效率的影响较大,45°、90°为破岩效率较高的2个极值点。3)刀间距为70和120mm时比能较小,破岩效率高。4)滚刀破岩以张拉破坏为主,剪切破坏为辅。研究结果可以为复合岩层中TBM刀盘设计及TBM施工提供一定的理论依据。     

围压对滚刀作用下节理岩体开裂特征影响的数值分析

为了研究围压对TBM滚刀破碎节理岩体机理的影响,采用颗粒流方法建立了二维TBM滚刀破岩数值模型。模型中,节理岩体的倾角45O,节理面间距50mm。围压分别为2.5 MPa、5 MPa、7.5 MPa、10 MPa和12.5MPa。计算了滚刀贯入岩体的力链分布、裂纹数量和破岩效率。研究表明,在低围压条件下,节理面对力链的传播具有阻碍作用。高围压下,这种阻碍作用降低;随着围压的增加,岩体的整体强度变高,微裂纹数量减少,岩体的破坏程度降低,破岩效率减小。     

基于岩碴粒径分布规律的TBM破岩效率分析

岩碴的形状、大小及其粒径分布规律是综合反映TBM破岩效率的重要指标,也是TBM掘进参数与岩石性质的重要联系。根据盘形滚刀破岩机制,对TBM掘进岩碴进行了现场量测和筛分试验,获得了TBM岩碴尺寸特征和粒径分布规律。在此基础上,对实测岩碴尺寸和粒径分布数据进行了统计分析和理论分布函数拟合。分析了粗糙度指数与岩石强度、岩石耐磨性的关系,探讨了不同围岩等级下粗糙度指数随掘进推力的变化规律。研究结果表明:①片状岩碴的长轴与短轴之比约为1.5,而长轴与厚度之比则差别较大,其长轴、短轴和厚度均服从正态分布;②不同岩性条件下岩碴粒径分布均符合Rosin–Rammler函数分布;③岩碴粗糙度指数越大,TBM破岩效率越高;硬岩条件下岩碴粗糙度指数随单轴饱和抗压强度增大而减小,而中硬—软岩条件下则相反;④无论是软岩还是硬岩,岩碴粗糙度指数随岩石耐磨性增大而减小,岩石耐磨性越强,TBM破岩效率越低;⑤TBM破岩效率与围岩等级密切相关,可根据现场实测岩碴粒径分布规律,确定Ⅱ级和Ⅲ级围岩条件下TBM破岩效率最佳时的掘进推力区间。     

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。     

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。     

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。     

盾构连续移动式冲击凿岩技术试验研究

TBM设备在硬岩掘进时,存在工作效率低下、滚刀磨损严重以及工作机构耗损严重等缺陷。严重降低了掘进效率,影响整机的性能。为了更加适应地层的开挖,通过对原有开挖刀盘进行分析,研究一种连续移动式冲击凿岩开挖技术。通过仿真分析法,对不同钻头落点位置模拟仿真,并通过试验法搭建试验平台,对气动潜孔锤和液压凿岩机分别进行试验,以验证凿岩能力。试验表明,连续移动冲击凿岩设备中,液压凿岩机比气动潜孔锤效果更明显,且方案具备可行性。利用TBM刀盘结合冲击破岩装置,可以使岩石单向受压,使岩石更容易破碎,先利用冲击形成预裂或临空面,再利用滚刀压裂,可有效提高掘进效率,并且减少了盾构施工过程中刀盘上的刀具磨损情况,增强了TBM设备在面对硬岩掘进的过程中对硬质地层的切削能力,可以有效地提高掘进设备对地层的适应性。     

Study on the influence of confining stress on TBM performance in granite rock by linear cutting test

Rock stress problems induced by overburden or anisotropic stresses are significant to the TBM tunneling. In this paper, the effect of different confining stressed conditions on TBM performance are investigated by using full-scale cutting tests with large intact granite specimens (1000 mm × 1000 mm × 600 mm). In these tests, the effects of confining stresses on the normal force, rolling force, the cutting coefficient and specific energy are analyzed. It is found that the confining stress has significant impact on the normal force and rolling force. Specifically, for the same cutting spacing and penetration depth, the normal force increases with increasing confining stress due to enhancement of the rock resistance strength; meanwhile the rolling force decreases gradually with increasing confining stress. The stress deviation between two confining directions affects the optimum penetration that corresponds to small specific energy. The results provide better understanding of the effect of confining stress on the TBM performance and also recommend some guidelines for TBM tunneling under stressed geological condition.     

Study on rock mass boreability by TBM penetration test under different in situ stress conditions

Rock mass boreability is a comprehensive parameter reflecting the interaction between rock mass and a tunnel boring machine (TBM). Many factors including rock mass conditions, TBM specifications and operation parameters influence rock mass boreability. In situ stress, as one of the important properties of rock mass conditions, has not been studied specifically for rock mass boreability in TBM tunneling. In this study, three sets of TBM penetration tests are conducted with different in situ stress conditions in three TBM tunnels of the Jinping II Hydropower Station. The correlation between TBM operation parameters collected during the tests and the rock mass boreability index is analyzed to reveal the influence of in situ stress on rock mass boreability and TBM excavation process. The muck produced by each test step is collected and analyzed by the muck sieve test. The results show that in situ stress not only influences the rock mass boreability but also the rock fragmentation process under TBM cutters. If the in situ stress is high enough to cause the stress-induced failure at the tunnel face, it facilitates rock fragmentation by TBM cutters and the corresponding rock boreability index decreases. Otherwise, the in situ stress restrains rock fragmentation by TBM cutters and the rock mass boreablity index increases. Through comparison of the boreability index predicted by the Rock Mass Characteristics (RMC) prediction model with the boreability index calculated from the penetration test results, the influence degree of different in situ stresses for rock mass boreability is obtained.     

Correlation of rock cutting tests with field performance of a TBM in a highly fractured rock formation: A case study in Kozyatagi-Kadikoy metro tunnel,Turkey

This paper presents and discusses detailed field and laboratory studies concerning boreability prediction of tunnel boring machines (TBMs) used in Kozyatagi-Kadikoy metro tunnels in Istanbul in a highly fractured rock formation. The determination of some design parameters and performance prediction of a tunnel boring machine (TBM) are carried out using full-scale rock cutting test. The intact rock samples having minimum sizes of 1.0 × 0.7 × 0.7 m are obtained from shale and limestone (Kartal Formation) along the tunnel line. The rock samples are subjected to full-scale laboratory rock cutting tests with different depth of cut and cutter spacing values using a constant cross section (CCS) disc cutter of 330 mm in diameter. Cutter forces, i.e., thrust force, rolling force and specific energy values are recorded for each cut. The results of the tests are first used to calculate TBM design and performance parameters such as torque and thrust requirements and cutting rates. In the second part of the research, the field performance of the TBM is recorded with the aid of data acquisition system installed within TBM and the predicted performance and design values obtained from full-scale rock cutting tests are compared with the field values. It is observed that fractured characteristics of the rock formation affect tremendously TBM performance and predicted values differ from the field data in some extend. It is believed that the results will serve as a guide for efficient selection and use of TBMs.     

钻爆法与TBM开挖深部洞室诱发围岩应变能释放规律

 在深部岩体开挖过程中,围岩应变能的释放是导致岩体破坏的诱因之一,而不同开挖方式下应变能的释放规律存在较大差异。通过理论分析,探讨了钻爆法和TBM开挖下能量的转化和分配机理,并对锦屏二级水电站深埋隧洞TBM和钻爆开挖导致的围岩振动进行现场监测和对比分析,讨论了不同开挖方式下应变能释放的过程及特性。研究表明,高地应力下爆破开挖过程岩体所储存的应变能伴随爆破破岩过程高速释放,且应变能诱发的振动能与爆炸能诱发的振动能大致相当,另外,MS1段释放的岩体应变能约为整个开挖过程应变能释放量的50%;而TBM开挖条件下,开挖岩体内应变能以准静态的方式缓慢释放,几乎全部转化为岩体势能,不会引起围岩动力响应。相同条件下,钻爆开挖所引起围岩释放的应变能的大小和速率均较TBM开挖大,导致相同条件下钻爆开挖的隧洞高等级岩爆发生的频次较多,而TBM开挖条件下以片帮、剥落为代表的破坏现象较为显著。     

二长花岗岩三轴压缩下声发射特征围压效应的试验研究

 岩石材料在受载情况下,发生变形和内部破裂,储存的部分能量以应力波的形式释放出来,产生声发射现象。采用三轴压缩试验和声发射试验,研究玲珑金矿二长花岗岩声发射特征与力学参数之间的关系。结果表明：(1) 岩石试样在三轴试验条件下,其声发射特征基本符合岩石加载破坏过程中的4个阶段,其中压密阶段在围压对岩石材料的压实作用下没有明显体现出来。(2) 通过分析围压对岩石记忆效应的影响得出,在相对低围压水平时,Kaiser效应显著性会随轴向应力水平提高而降低,Felicity效应显著增大;随着围压水平的提高,Kaiser效应显著增大,Felicity效应显著降低。(3) 在声发射法测量地应力过程中采用三轴试验更为适合,三轴试验可消除应力环境不同和高应力水平Kaiser效应模糊所引起的误差,使测量值更接近实际岩体所处的应力状态。(4) 随着围压水平的提高,岩石的抗压强度随之提高,岩石破裂前夕声发射特征参数呈现突发性特征,表现为突然激发出高能量振铃计数率、能量累积迅猛增加,并且伴随没有峰后曲线的岩石突然破裂现象。     

不同TBM掘进速率下洞室围岩开挖扰动区研究

 在不同卸荷速率下三轴加卸载室内试验成果的基础上,以Hoek-Brown经验强度准则为依据,拟合出在不同卸荷速率下板岩的力学参数(黏聚力和内摩擦角)。在分析TBM掘进特点的基础上,提出能反映其特点的数值模拟方法,并在FLAC3D程序中引入加卸载准则,对不同掘进速率下隧洞围岩的开挖扰动效应进行数值模拟研究。结果显示：掘进速率越快,围岩开挖扰动效应越小,围岩越稳定;隧洞围岩在开挖后变形较为均匀;在隧洞的径向,位移和应力变化较为明显的呈现为3个区域,即强变化区、弱变化区和平稳区;最大主应力随着洞径方向逐渐由单向应力状态向二向应力状态和三向应力状态转变,第二偏应力不变量在隧洞轴向方向形成一闭合的应力集中区域,称为“应力墙”,该区域在TBM掘进过程中对刀头切割岩体达到破岩的效果极为有利;隧洞围岩开挖扰动区随TBM掘进速率变化较大,当掘进速率增加一倍后,其扰动区由1.1 m降低到0.4 m,减小了64%。     

Stress dependency of the Cerchar abrasivity index (CAI) and its effects on wear of selected rock cutting tools

The abrasiveness of rocks is often described by the Cerchar abrasivity index CAI. However, the state of stress of the rock sample with the standard CAI test in the laboratory is different from the state of stress of rock to be excavated at the face of any underground opening. Until this work, no attempt has been made to estimate if and how the CAI is effected by in situ stresses. This paper demonstrates that the CAI is definitely stress-dependent. A novel test procedure in which the CAI tests is conducted on samples in a triaxial cell shows the stress dependency for various rock types by higher CAI values upon confining pressure. Additionally, the states of stress at the face of different underground openings are discussed and application of the elevated CAI values for estimating wear of roadheader picks and TBM discs is given.