Experimental and analytical studies of the parameters influencing the action of TBM disc tools in tunnelling

The use of tunnel boring machines (TBMs) is increasingly popular in tunnelling. One of the most important aspects in the use of these machines is to assess with certain accuracy the effectiveness of the action of the discs on the cutter-head in the different rock types to be excavated. A specific machine, called an intermediate linear cutting machine (ILCM), has been developed at the Politecnico di Torino in order to study, on a reduced scale in detail in the laboratory, the interaction between the discs of the TBM and the rock: this machine allows a series of grooves to be cut on a rock sample of 0.5 × 0.3 × 0.2 m, through the rolling of a 6.5-in. disc, and evaluation, during testing, of the parameters associated with the action of the cutting tool. The parameters measured during the tests were compared with the results obtained employing two analytical methods widely used for predicting the performance of TBMs: the Colorado School of Mines (CSM) model and the Norwegian University of Science and Technology (NTNU) model. The latter showed a greater ability to reproduce tests conducted using the ILCM. However, as with the CSM model, it does not allow the optimal excavation condition (the ratio, which minimizes the specific energy of excavation, between the groove spacing and the penetration of the disc), necessary for the correct design of the TBM cutter-head, to be identified. An example, based on a real case of a tunnel in Northern Italy, allowed a demonstration of how the NTNU model provides results in line with the measurements taken during the excavation and represents, therefore, a model that is able to reliably simulate both laboratory tests and the action of a TBM on site. The NTNU model, together with the results of the tests with ILCM targeted on the identification of the optimal conditions of excavation, may allow the correct dimensioning of the TBM cutter-head to be attained in order to effectively implement the excavation.     

Comparison and correlation between the laboratory,semi-theoretical and empirical methods in predicting the field excavation performance of tunnel boring machine (TBM)

Acta Geotechnica - Many methods have been proposed to predict the field excavation performance of tunnel boring machine (TBM). They can usually predict the general trends of the field rock cutting...     

Theoretical and Experimental Results from Laboratory Tests by ILCM

The intermediate linear cutting machine (ILCM) is a machine designed to work on an intermediate scale between the full- and the small-scale. The reduced scale involves several advantages compared to full-scale tests, especially in terms of sample supplying and transportation. On the other hand, it has an impact on the testing conditions, resulting in a limitation of the cutting penetration and spacing during the test, as well as in a smaller disc cutter. This affects most of the results, which cannot be directly used for the on-site machine performance prediction. However, some experimental results provided in the literature show that the optimal spacing/penetration ratio is not significantly affected by the changes involved. On this basis, the results obtained from ILCM tests should provide reliable information about the optimal cutting conditions of a tunnel boring machine in massive rock mass. The work performed included the development of some improvements of the testing rig, as well as a modified ILCM testing procedure, according to the one typically used in standard LCM tests. The results provide information about the attitude of the tested lithotypes to mechanical excavation by means of disc tools, including the optimal cutting conditions. Additional work was developed in terms of detailed characterisation of the rock samples involved and assessment of the size distribution of the debris produced during the ILCM tests. Nevertheless, further tests are necessary, in order to assess the consistency of the experimental procedure employed and to investigate the scale effect.

     

大线速度下超高压水射流破岩试验研究

高压水射流的破岩效果对高压水射流辅助掘进机破岩技术至关重要。为提升隧道掘进机工况下高压水射流辅助破岩的效率,开展大线速度下超高压水射流破岩试验,分析喷嘴移动线速度、射流压力和喷嘴直径对破岩效果的影响规律,并探究加磨料和射流形式对破岩效果的影响。试验结果表明,随喷嘴移动线速度增加,高压水射流的切割深度和切割宽度均近似线性减小;随射流压力增加,切割深度近似线性增大,压力从200 MPa提高到280 MPa,切割深度增加了72%～82%;喷嘴直径从0.35 mm增大到0.60 mm,切割深度增加了60%～85%。大线速度下加磨料后射流变发散,加磨料的切割深度小于纯水的切割深度,加磨料的切割宽度大于纯水的切割宽度。砂管束流射流模式的能量利用率更高,砂管束流的切割深度比长线射流的切割深度大35%～42%,砂管束流的切割宽度比长线射流的切割宽度大78%～85%。基于Crow切割岩石理论,通过试验数据回归分析,得到大线速度下超高压水射流切割深度半理论半经验预测模型,可为高压水射流辅助掘进机破岩技术中射流切割参数优化提供参考依据。研究成果对提升隧道掘进机工况下超高压水射流辅助破岩的效率是很有意义的。     

Developing new equations for TBM performance prediction in carbonate-argillaceous rocks: a case history of Nowsood water conveyance tunnel

Nowsood water conveyance tunnel is 49 km long and has been designed for transferring 70 m³/s water from Sirvan river southward to Dashte Zahab plain in the west of Iran. This long tunnel has been divided into three sections, namely 1A, 1B and 2. By April 2008, about 5.3 km of the lot 2 of this project, with a total length of 26 km, were excavated by a double-shield TBM. The bored section of tunnel passed through different geological units of three main formations of the Zagross mountain ranges which mainly consist of weak to moderately strong argillaceous-carbonate rocks. This paper will offer an overview of the project, concentrating on the TBM operation, and review the results of the field performance of the machine. Also results of statistical analyses to evaluate correlation of TBM performance parameters with rock mass characteristics will be discussed. The results of machine performance analysis indicated that there are strong relationships between geomechanical parameters and TBM performance parameters in this particular project. In this research some empirical equations and a chart have been developed to estimate TBM performance parameters in similar cases based on common rock mass properties.     

A spatial estimation model for continuous rock mass characterization from the specific energy of a TBM

Summary  Basic principles of the theory of rock cutting with rolling disc cutters are used to appropriately reduce tunnel boring machine (TBM) logged data and compute the specific energy (SE) of rock cutting as a function of geometry of the cutterhead and operational parameters. A computational code written in Fortran 77 is used to perform Kriging predictions in a regular or irregular grid in 1D, 2D or 3D space based on sampled data referring to rock mass classification indices or TBM related parameters. This code is used here for three purposes, namely: (1) to filter raw data in order to establish a good correlation between SE and rock mass rating (RMR) (or tunnelling quality index Q) along the chainage of the tunnel, (2) to make prediction of RMR, Q or SE along the chainage of the tunnel from boreholes at the exploration phase and design stage of the tunnel, and (3) to make predictions of SE and RMR or Q ahead of the tunnel’s face during excavation of the tunnel based on SE estimations during excavation. The above tools are the basic constituents of an algorithm to continuously update the geotechnical model of the rock mass based on logged TBM data. Several cases were considered to illustrate the proposed methodology, namely: (a) data from a system of twin tunnels in Hong Kong, (b) data from three tunnels excavated in Northern Italy, and (c) data from the section Singuerlin-Esglesias of the Metro L9 tunnel in Barcelona. Correspondence: G. Exadaktylos, Department of Mineral Resources Engineering, Technical University of Crete, Chania, Greece     

TBM Performance Analysis in Pyroclastic Rocks: A Case History of Karaj Water Conveyance Tunnel

Karaj Water Conveyance Tunnel (KWCT) is 30-km long and has been designed for transferring 16 m³/s of water from Amir-Kabir dam to northwest of Tehran. Lot No. 1 of this long tunnel, with a length of 16 km, is under construction with a double shield TBM and currently about 8.7 km of the tunnel has been excavated/lined. This paper will offer an overview of the project, concentrating on the TBM operation and will review the results of field performance of the machine. In addition to analysis of the available data including geological and geotechnical information and machine operational parameters, actual penetration and advance rates will be compared to the estimated machine performance using prediction models, such as CSM, NTNU and Q_TBM. Also, results of analysis to correlate TBM performance parameters to rock mass characteristics will be discussed. This involves statistical analysis of the available data to develop new empirical methods. The preliminary results of this study revealed that the available prediction models need some corrections or modifications to produce a more accurate prediction in geological conditions of this particular project.     

深埋隧洞极强岩爆段隧道掘进机半导洞掘进岩爆风险研究

深埋隧洞TBM（隧道掘进机）全断面掘进时,在局部超高应力集中的完整硬脆性岩体洞段将直面极强岩爆的风险,设备和人员的安全将遭受极大的威胁。在锦屏II水电站3#引水隧洞极强岩爆段实施了“先半导洞+TBM联合掘进”实验,结合微震实时监测信息对TBM半导洞掘进的岩爆风险开展了研究。监测结果表明,（1）TBM半导洞掘进期间,日平均微震事件数、日平均辐射微震能、微震大事件数及实际岩爆发生次数和强度均远远低于TBM全断面掘进;（2）能量指数对数值和累积视体积的时域演化表明,TBM半导洞掘进强烈岩爆发生的风险远低于TBM全断面掘进,现场实际开挖也证明了这一点;（3）半导洞洞段微震事件的空间集结程度、总数、震级大小与能量辐射均远小于全断面洞段。因此,TBM半导洞掘进的岩爆风险远远低于TBM全断面掘进,在具有施工条件的情况下采用先半导洞预处理,然后TBM半断面掘进极强岩爆段,以期控制岩爆风险的方案是可行的。     

A Study of Optimal Rock-Cutting Conditions for Hard Rock TBM Using the Discrete Element Method

The efficiency of TBM performance affected by the specific s/p (s: spacing and p: penetration) ratio of the disc cutter is a research issue in demand. This article presents a multi-indentation simulation using discrete element method (DEM) analysis to study the optimal rock-cutting phenomena in terms of the interaction of the s/p ratio with intact rock properties. The multi-indentation simulation attempts to represent a linear cutting machine (LCM) test, which is a full-scale test for evaluating the optimal rock-cutting condition and measuring required reaction forces based on the intact rock condition in general practice. A governing equation relating mechanical rock properties with geometric characteristics for the optimal rock-cutting condition is derived by the numerical simulation, and its performance is evaluated with the result of the laboratory LCM tests. The results of simulations and real LCM tests show that the effective rock-cutting condition corresponding to the minimum specific energy can be estimated by an optimized s/p ratio, which, in turn, is linearly proportional to the square of the material brittleness, B ², and cutter tip width, t (i.e., s/p?=?cB ² t, where c is coefficient). The limitation of the numerical simulation associated with the sample preparation is also discussed.     

复合地层隧道围岩强度实时估算研究

隧道TBM开挖过程中经常会遇到复合岩层,在这种地质环境下,隧道掘进机（tunnel boring machine,简称TBM）开挖过程中的隧道围岩强度很难估计,隧道开挖掌子面和围岩容易发生坍塌。为了提高隧道掘进效率、预防事故发生,对开挖隧道围岩强度进行实时估算方面的研究很有必要。在重庆轨道九号线隧道TBM施工中,通过室内试验和现场实测数据发现,TBM推力F_N与岩石强度成正比、TBM扭矩推力比T/F_N（T为扭矩）与贯入度p^0.5成正比例关系。针对砂质泥岩、砂岩和灰岩组成的复合岩层,提出了一种利用现场实测推力F_N和扭矩T的值来快速估算开挖隧道围岩强度的方法,进一步对TBM实测数据进行线性拟合,从而得到估算公式中两个常数α₁、α₂的取值方法,并在10多个隧道实际工程中得到验证。结果表明,对于这种复合岩层地质环境,两个常数α₁、α₂的值与滚刀数量n和滚刀直径d相关。该研究成果为实时快速估算开挖隧道围岩强度提供了一种新的切实可行的思路,能提高隧道TBM施工的可靠性和安全性,具有重要的应用价值。     

TBM在不良地质洞条件下的施工技术

TBM掘进机以其快速、高效、安全、优质等优点越来越广泛地被应用于隧洞开挖施工中,尤其更适用于深埋超长隧洞,然而在不良地质洞段中TBM掘进缓慢,甚至有卡刀可能,反而不如钻爆法灵活,这就需要根据围岩性状采取特殊技术处理措施,辅以监控量测手段对支护方案进行验证、调整支护措施、修正设计参数等。结合辽宁大伙房输水隧洞工程,总结了在不良地质洞条件下的超前地质预报方法、不良地质段处理措施以及围岩变形监测方法。     

New equations for predicting the field penetration index of tunnel boring machines in fractured rock mass

The Queens Water Tunnel No. 3, stage 2 having 7.5-km length and 7-m diameter, is excavated by a high-power tunnel boring machine (TBM) underneath Brooklyn and Queens area for distributing freshwater throughout the New York City, USA. This paper offers a review of the project by considering the TBM performance and rock mass interaction. Using the individual cutter force, intact, and mass rock properties, TBM performance by means of field penetration index (FPI) was predicted and compared with actual results obtained in the field. Further, the study involves statistical analysis of the laboratory and field data including machine, intact, and mass rock properties to develop new empirical equations to estimate FPI. It is stated that the FPI, also converted to the rate of penetration, could be estimated utilizing intact and mass rock properties together with cutter force for similar type of rocks with correlation coefficient of 0.88.     

考虑邻近土洞影响的盾构掘进速度控制

盾构机穿越邻近土洞区域是在岩溶区修建的地铁隧道常常遇到的问题,为降低盾构掘进对土洞的扰动,以防止盾构突陷、偏离轴线或发生地面塌陷,需对穿越时盾构的掘进参数进行优化控制。针对当前主要根据经验选取掘进参数的不足,根据弹性力学Mindlin解建立了盾构穿越邻近土洞的力学模型,在此基础上,以掘进速度为控制变量,以掘进引起土洞顶部能量密度变化为指标函数,提出了穿越时的掘进速度最优控制问题,并利用梯度法进行了数值求解,最后将该方法运用于广州地铁九号线花-马区间盾构穿越邻近土洞问题的分析中。结果表明:该模型能有效反映盾构掘进时正面推力对土洞顶部的扰动;在该模型上建立的掘进速度最优控制问题,能对掘进速度的控制策略进行优化,优化结果与工程经验相符,具有一定工程应用价值。     

煤矿井下随掘地震震源特征及探测性能研究

煤矿智能化背景下,随掘地震已经成为掘进工作面安全掘进的地质保障关键技术之一,可实时、超前、精细探明掘进前方的隐蔽地质构造,如采空区、断层、陷落柱等,有效促进掘进生产安全高效。不同于广泛采用的反射槽波超前探测技术,随掘地震采用了掘进机掘进时震动信号作为激发源,替代了常规地震勘探中的炸药震源,具有震源绿色、安全、成本低、可重复、探掘同步等优点。由于掘进机震源在激发方式、能量、频率、带宽等方面与炸药震源差别较大,因此其探测性能受到很多关注。从随掘地震的震源机制、波场特征、传播距离、成像准确率等方面进行研究,详细分析其探测性能,认为随掘地震波场中槽波和横波发育,可利用槽波或横波进行超前探测;Y分量具有更好的信噪比优势,但在实际应用时考虑到反射面的走向,相同设备量情况下,Z分量更有优势;随掘地震的直达横波传播距离可达700 m以上,横波超前探测距离可达到300 m以上;随掘地震的直达槽波传播距离可达400 m 以上,槽波超前探测距离可达到170 m以上;常规掘进速度下,反射波叠加次数可达到16次,相比常规的一次探测,信噪比可提升4倍,有效提高了探测精度和准确度。后续将通过大量的随掘应用数据进一步修正随掘地震技术的性能参数。      

Mechanical response of surrounding rock of tunnels constructed with the TBM and drill-blasting method

There are two kinds of excavation methods in underground engineering: the tunnel boring machine (TBM) and the drill-blasting method. A large number of studies have shown that the deformation and failure, the degree of disturbance, the stability and the reinforcement measures of surrounding rock using the TBM and drill-blasting method vary from each other. To accurately master these macroscopic damages, it is necessary to focus on the investigation of the micro-mechanical responses of the surrounding rock. Scanning electron microscopy tests, acoustic emission tests and tunnel acoustic detection tests were carried out to analyze the mechanical response of surrounding rock of tunnels, which were excavated in marble by, respectively, the TBM and the drill-blasting method. The tests results showed that most of the rock fractures cut by TBM is wipe along the crystal, and the failure mechanism is mainly cutting, while most of the rock fractures induced by the TBM coincide with crystal planes, its mechanism is mainly tensile. The stress–strain curves of rocks cut by the TBM method are rather flat around the peak strength, which means a strong resistance to deformation around the peak load. The response of AE for the rock cut by the TBM method appears after larger strains than the response of the rock constructed by the drill-blasting method. This suggests that the resistance to damage is higher under TBM excavation conditions. The relaxation depths of the tunnel excavated by the drill-blasting method are larger than the tunnel excavated by the TBM method. The research can provide more insight into tunnel failure mechanisms and provide a framework for reinforcement measures.     

Roadheader performance prediction using genetic programming (GP) and gene expression programming (GEP) techniques

Roadheading machines play a vital role in excavation operation in tunneling and mining industries notably when selective mining is required. Roadheaders are more effective in soft to medium rock formations due to a higher cutting rate in such strata. A precise prediction of machine’s performance is a crucial issue, as it has considerable effects on excavation planning, project’s cost estimation, machine specification selection as well as safety of the project. In this research, a database of machine performance and some geomechanical parameters of rock formations from Tabas coal mine project, the largest and fully mechanized coal mine in Iran, has been established, including instantaneous cutting rate (ICR), uniaxial compressive strength, Brazilian tensile strength, rock quality designation, influence of discontinuity orientation (Alpha angle) and specific energy. Afterward, the parameters were analyzed through genetic programming (GP) and gene expression programming (GEP) approaches to yield more accurate models to predict the performance of roadheaders. As statistical indices, coefficient of determination, root mean square error and variance account were used to evaluate the efficiency of the developed models. According to the obtained results, it was observed that developed models can effectively be implemented for prediction of roadheader performance. Moreover, it was concluded that performance of the GEP model is better than the GP model. A high conformity was observed between predicted and measured roadheader ICR for GEP model.     

深埋隧洞不同开挖方式下即时型岩爆微震信息特征及能量分形研究

基于锦屏二级水电站深埋隧洞钻爆法及隧道掘进机（TBM）开挖过程中大量微震监测数据及不同等级的岩爆案例,对不同开挖方式下即时型岩爆的孕育及发生过程的能量释放展开研究,并运用分形几何原理研究微震能量分布的变化规律,得到以下结论：（1）即时型岩爆的孕育及发生过程中,岩爆区围岩岩体处于破坏加速集聚并不断扩展的过程;（2）钻爆法开挖过程中储存在岩体内的弹性应变能消耗于岩体破裂过程大于TBM开挖,而转化为岩体动能小于TBM开挖;（3）钻爆法开挖微震能量分形维度在即时型岩爆的孕育过程不断增加,岩爆临近前会增加到某个临界值以上;（4）TBM开挖即时型高等级岩爆能量分形维度值大于钻爆法开挖,并且其分形维度值可以反映低等级岩爆伴随发生的特征。     

Applying Optimized Support Vector Regression Models for Prediction of Tunnel Boring Machine Performance

One of the main factors in the effective application of a tunnel boring machine (TBM) is the ability to accurately estimate the machine performance in order to determine the project costs and schedule. Predicting the TBM performance is a nonlinear and multivariable complex problem. The aim of this study is to predict the performance of TBM using the hybrid of support vector regression (SVR) and the differential evolution algorithm (DE), artificial bee colony algorithm (ABC), and gravitational search algorithm (GSA). The DE, ABC and GSA are combined with the SVR for determining the optimal value of its user defined parameters. The optimization implementation by the DE, ABC and GSA significantly improves the generalization ability of the SVR. The uniaxial compressive strength (UCS), average distance between planes of weakness (DPW), the angle between tunnel axis and the planes of weakness (α), and intact rock brittleness (BI) were considered as the input parameters, while the rate of penetration was the output parameter. The prediction models were applied to the available data given in the literature, and their performance was assessed based on statistical criteria. The results clearly show the superiority of DE when integrated with SVR for optimizing values of its parameters. In addition, the suggested model was compared with the methods previously presented for predicting the TBM penetration rate. The comparative results revealed that the hybrid of DE and SVR yields a robust model which outperforms other models in terms of the higher correlation coefficient and lower mean squared error.     

截齿滚动掘进冻土过程的影响因素数值模拟研究

为了解决竖井冻土开挖难度大、人工挖掘效率低的问题,研究发明了一种新型重力式竖井掘进机,该掘进机利用截齿连续滚动向下、行走式掘进冻土,在竖井冻土掘进中具有较好的适应性,而截齿侵入深度是影响掘进冻土效率的重要因素。先采用三维软件建模,通过霍普金森压杆冲击试验,结合HJC压缩损伤模型原始参数,优化得到冻土本构模型参数;再利用有限元分析软件耦合,模拟截齿在不同侵入深度下滚动掘进冻土,得到冻土在不同凹陷破坏深度下的截齿三向力、冻土应力和应变的变化规律,便于直观研究截齿掘进冻土过程,寻求最优截齿侵入深度。仿真结果表明：随着截齿侵入深度增加,截齿三向力变大,冻土凹陷面积扩大,冻土应力向下无边界扩展递减;冻土与截齿接触区域应力、应变最大,远离截齿作用时冻土区域的应力、应变逐渐递减,其变化规律与截齿连续滚动掘进冻土特征相关;当冻土单轴抗压强度为9 MPa时,截齿滚动掘进冻土过程存在最优截齿侵入深度,为4 cm,此时冻土破坏特征明显,截齿滚动掘进冻土效率最高且能耗低。