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Abstract

Penetration rates during excavation using hard rock tunnel boring machines (TBMs) are significantly influenced by the degree of fracturing of the rock mass. In the NTNU prediction model for hard rock TBM performance and costs, the rock mass fracturing factor (ks) is used to include the influence of rock mass fractures. The rock mass fracturing factor depends on the degree of fracturing, fracture type, fracture spacing, and the angle between fracture systems and the tunnel axis. In order to validate the relationship between the degree of fracturing and the net penetration rate of hard rock TBMs, field work has been carried out, consisting of geological back-mapping and analysis of performance data from a TBM tunnel. The rock mass influence on hard rock TBM performance prediction is taken into account in the NTNU model. Different correlations between net penetration rate and the fracturing factor (ks) have been identified for a variety of ks values.

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... This data is presented for three dominant joint sets (excluding random joints) in each rock formation along the tunnel route from chainage 37+500 to 27+000. The rock mass fracturing factor (k s ) as defined by the NTNU model has been developed as a parameter to incorporate the fracture class (presented in Table 4) and the angle between the tunnel axis and the planes of weakness (according to Eq. (3)) (Yagiz 2003;Macias et al. 2014). According to this classification, fractures (joints/fissures) are classified based on the average spacing or the range of spacing between the planes of the weakness. ...
... k s for a joint set is calculated using the charts shown in Fig. 5a (Bruland 1998). In the case of low fracture classes (0, I, and II), a detailed determination of fracture class is essential, which can be found by interpolated curves using linear interpolation between the given curves as shown in Fig. 5b (Macias et al. 2014). In cases where more than one joint set is present, the total fracturing factor is calculated using Eq. ...
... Calculation of fracturing factor (k s ) based on the angle between the tunnel axis and the plane of weakness and fracture class; b interpolated curves for low fracture classes (i.e., joints: 0-I and fissures: 0-II)(Macias et al. 2014) along the completed portion of the tunnel which can facilitate objective evaluation of the cutter life versus rock abrasivity. ...
Article
Disc cutters wear and need to be replaced when using tunnel boring machines (TBMs) to excavate through rock, often becoming a high ticket item on the list of consumables in tunneling operation. The empirical models used for predicting cutter life are commonly based on the properties of intact rock, while the impact of rock mass characteristics on cutter wear is often ignored or not properly taken into account. Joints and discontinuities tend to decrease the strength of rock mass, as compared to intact rock. Joint properties can affect the interactions between the rock and the disc cutter in the boring process. In other words, the cutter wear and life in a jointed rock mass are different than the wear rate in intact rock. In this study, field data including the geomechanical parameters and observed cutter life in the Kerman water conveyance tunnel (KWCT) project was analyzed using multivariable regression to offer a new empirical prediction model for prediction of cutter life in the jointed rocks. The model presented in this study shows that cutter life is a function of the total fracturing factor and rock mass strength, representing rock mass properties and Cerchar abrasivity index as intact rock property. Furthermore, boring in jointed rock is easier than an intact rock, and as a result, the cutter life increases. The validation results show that this model can offer a more accurate prediction of the disc cutter life in tunneling projects involving jointed rock masses.
... Figure 6 shows correlations of the rock mass fracturing factor (k s ) with the net penetration rate (m/h) and cutter thrust (kN/cutter). Good correlations are obtained in both cases which conform the findings by Bruland (1998) and Macias et al. (2014b). The significant decreasing of the thrust relation is due to operational reasons to avoid damage and excessive wear to the cutters as well as due to avoid the collapse of the muck transportation system. ...
... -The rock mass fracturing factor (k s ) has been proven to be a good representative of the rock mass influence on performance prediction in agreement with Macias et al., (2014b). -Good level of predictions has been obtained by using the NTNU model for the section studied. ...
Conference Paper
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Tunnel boring has shown to be a suitable excavation method on underground expansion. Mining development requires often long tunnels with limited access points which have to be constructed on a limited amount of time. In many cases, Tunnel Boring Machines (TBMs) can be a good choice of tunnelling method. Planning and risk management is of greater importance for technical successfulness and economic benefit on tunnel boring compared to drill and blast tunnelling. Therefore, good predictions of performances and excavations costs take great importance for this issue. A complete analysis of geological mapping from probe drilling cores, rock drillability testing and TBM log data has been performed in order to analyze performances on a hard rock TBM used in mining development. Assessments and comparison between actual and performance predictions by using the NTNU prediction model for hard rock TBMs has been carried out.
... The Norwegian University of Science and Technology (NTNU, former NTH) has a long history of developing prognosis models for the heavy construction industries (Macias et al. 2014a). These models comprise D&B tunneling time and cost, hard rock TBM time, tool life and cost, soft ground TBM tool life, and rock quarrying capacities and cost (Bruland 1998a;Zare and Bruland 2013;Jakobsen et al. 2013). ...
... The DRI has been selected as the drillability parameter of intact rock. It is an indirect measure of the breaking work required, and an effective gauge of the rock breaking process under a cutter (Macias et al. 2014b). DRI is a combination of the S 20 that expresses the amount of energy required to crush the material and the Sievers J-value SJ that characterizes the depth a cutter can be thrust into the rock (Bruland 1998c). ...
Article
Full-text available
Thorough and realistic performance predictions are among the main requisites for estimating excavation costs and time of the tunneling projects. Also, NTNU/SINTEF rock drillability indices, including the Drilling Rate Index™ (DRI), Bit Wear Index™ (BWI), and Cutter Life Index™ (CLI), are among the most effective indices for determining rock drillability. In this study, brittleness value (S20), Sievers’ J-Value (SJ), abrasion value (AV), and Abrasion Value Cutter Steel (AVS) tests are conducted to determine these indices for a wide range of Iranian hard igneous rocks. In addition, relationships between such drillability parameters with petrographic features and index properties of the tested rocks are investigated. The results from multiple regression analysis revealed that the multiple regression models prepared using petrographic features provide a better estimation of drillability compared to those prepared using index properties. Also, it was found that the semiautomatic petrography and multiple regression analyses provide a suitable complement to determine drillability properties of igneous rocks. Based on the results of this study, AV has higher correlations with studied mineralogical indices than AVS. The results imply that, in general, rock surface hardness of hard igneous rocks is very high, and the acidic igneous rocks have a lower strength and density and higher S20 than those of basic rocks. Moreover, DRI is higher, while BWI is lower in acidic igneous rocks, suggesting that drill and blast tunneling is more convenient in these rocks than basic rocks.
... Geological uncertainties experienced during a tunneling project can pose severe threats to the construction progress by causing operational delay, casualties, cost overrun, etc. (Delisio and Zhao 2014;Li et al. 2017;Macias et al. 2014;Zhu et al. 2021). There is a financial limitation for conducting geological/geotechnical tests for a tunneling project. ...
... Despite the attempts made so far, detailed studies are still required to characterize different tunneling responses caused by various adverse geologic conditions in rock strata. Potential adverse geologies encountered during tunneling operation in rock strata include karst caves, faults or fractured zones, rockburst, blocky rock, etc. (Jeong et al. 2018;Macias et al. 2014;Rostami 2016). Rock tunneling in karst or fault fractured zones can cause detrimental tunneling responses, such as TBM blockage, tunnel boundary collapse, water inrush, etc. (Huang et al. 2018;Parise et al. 2008). ...
Article
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This research proposes a model for early prediction of collapse incidents in rocks during tunnel boring machine (TBM) operation utilizing TBM and geological survey data. Uncertainties associated with tunnel geology can significantly hamper tunneling progress. So far, various research works have tried to reduce such uncertainties by predicting the geological condition during tunnel excavation. However, specific tunneling responses caused by adverse geology are still poorly studied. In rocks, adverse geology such as karstic caves and fault zones can cause tunnel boundary collapse, a detrimental tunneling response causing unexpected interruptions and casualties. To identify and predict the potential collapse of TBM tunnels in rocks, three machine learning (ML) classifiers are used, namely: (1) multilayer perceptron, (2) support vector machine, and (3) random forest. The ML algorithms are trained and validated using data on collapse incidents in a water conveyance tunneling project in China. The prediction accuracy of the proposed model reached 98% for training data and 97% for validation data. Furthermore, the model can identify an “Influence Zone” for a collapse incident. A unique contribution of this research is that the “Influence Zone” enables the model to predict an impending tunnel collapse and the extent of that collapsed segment ahead of the excavation. Finally, to gain better insight into the ML-based predictions, the relationships between TBM-related features and tunnel geology are carefully analyzed.
... They include various input parameters such as rock strength, as well as cutter geometry and machine specifications to estimate the penetration rate. The most important and well-known models are those by Colorado School of Mines (Rostami 2016;Rostami et al. 1994) and Norwegian model developed by NTNU in Trondheim (Bruland 1999;Macias et al. 2014). The study of preconditioning rock by microwave and the related impacts on TBM performance in this study is based on the CSM-model. ...
... Besides the difference in methods used, parameters of the adopted rock could also affect the range of k. These parameters include rock strength, rock boreability, rock mass fracturing, etc. (Sapigni et al. 2002;Bilgin et al. 2012Bilgin et al. , 2016Macias et al. 2014). Bilgin et al. (2012Bilgin et al. ( , 2016 found that the strength of rock mass is an important parameter in determining the thrust values, the torque values, and the type of cutters for a TBM. ...
Article
The influence of confining stress on rock breakage by a tunnel boring machine cutter was investigated by conducting sequential indentation tests in a biaxial state. Combined with morphology measurements of breaking grooves and an analysis of surface and internal crack propagation between nicks, the effects of maximum confining stress and minimum stress on indentation efficiency, crack propagation and chip formation were investigated. Indentation tests and morphology measurements show that increasing a maximum confining stress will result in increased consumed energy in indentations, enlarged groove volumes and promoted indentation efficiency when the corresponding minimum confining stress is fixed. The energy consumed in indentations will increase with increase in minimum confining stress, however, because of the decreased groove volumes as the minimum confining stress increases, the efficiency will decrease. Observations of surface crack propagation show that more intensive fractures will be induced as the maximum confining stress increases, whereas the opposite occurs for an increase of minimum confining stress. An observation of the middle section, cracks and chips shows that as the maximum confining stress increases, chips tend to form in deeper parts when the minimum confining stress is fixed, whereas they tend to formed in shallower parts as the minimum confining stress increases when the maximum confining stress is fixed.
... Many studies have been conducted in order to demonstrate the effects of rock (mass and material) properties on DRI (e.g. Wijk 1989; Karpuz et al. 1990;Kahraman 1999;Kahraman et al. 2000Kahraman et al. , 2003Hoseinie et al. 2009;Dahl et al. 2012;Yarali and Soyer 2013;Macias et al. 2014;Tripathy et al. 2015;Ataei et al. 2015). A penetration rate model was proposed using stepwise linear regression analysis in the study conducted by Selim and Bruce (1970). ...
Article
Full-text available
The purpose of this paper is to provide a proper, practical and convenient drilling rate index (DRI) prediction model based on rock material properties. In order to obtain this purpose, 47 DRI tests were used. In addition, the relevant strength properties i.e. uniaxial compressive strength and Brazilian tensile strength were also used and selected as input parameters to predict DRI. Examined simple regression analysis showed that the relationships between the DRI and predictors are statistically meaningful but not good enough for DRI estimation in practice. Moreover, multiple regression, artificial neural network (ANN) and hybrid genetic algorithm (GA)-ANN models were constructed to estimate DRI. Several performance indices i.e. coefficient of determination (R2), root mean square error and variance account for were used for evaluation of performance prediction the proposed methods. Based on these results and the use of simple ranking procedure, the best models were chosen. It was found that the hybrid GA-ANN technique can performed better in predicting DRI compared to other developed models. This is because of the fact that the proposed hybrid model can update the biases and weights of the network connection to train by ANN.
... Zhao et al. [5] found that an increase in fracture spacing (reduction in fracture frequency) lead to a reduction in productivity, with maximum productivity attributed to a relative joint strike of 60 degrees to the tunnel axis. Macias et al. [6], however, found a negative correlation with the rock mass fracturing factor (ks). ...
Article
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Boreability can be defined as the ability of a bore to penetrate a rock mass. Understanding the factors influencing boreability is critical for enhanced project planning and reduce geotechnical risk in an offshore shaft boring environment. Large diameter drills are used for offshore shaft boring, which can be up to 7 m in diameter, and therefore more akin to tunnel boring machines due to the scale of the excavation and extent of ground interaction. With increases in bore diameter, there is a need to properly define and evaluate the effect of the degree of rock mass fracturing on machine performance for improved estimates of boreability. Discrete Fracture Network (DFN) simulation has been used as an innovative approach for stochastic realisation of rock mass fracturing by determination of the P32 volumetric fracture intensity in the context of boreability. P32 shows positive trend to specific penetration (SP), with maximum SP being achieved at moderate to high fracturing levels (20 - 25m⁻¹). However, in this case, P32 shows a similar positive trend to P10, but with peak SP appearing at higher intensity levels. Increased RQD values result in reduced SP, with peak SP reached at moderate fracturing levels, similar to P10.
... Besides the difference in methods used, parameters of the adopted rock could also affect the range of k. These parameters include rock strength, rock boreability, rock mass fracturing, etc. (Sapigni et al. 2002;Bilgin et al. 2012Bilgin et al. , 2016Macias et al. 2014). Bilgin et al. (2012Bilgin et al. ( , 2016 found that the strength of rock mass is an important parameter in determining the thrust values, the torque values, and the type of cutters for a TBM. ...
Article
Full-text available
Cutter spacing is an essential parameter in the TBM design. However, few efforts have been made to study the optimum cutter spacing incorporating penetration depth. To investigate the influence of pre-set penetration depth and cutter spacing on sandstone breakage and TBM performance, a series of sequential laboratory indentation tests were performed in a biaxial compression state. Effects of parameters including penetration force, penetration depth, chip mass, chip size distribution, groove volume, specific energy and maximum angle of lateral crack were investigated. Results show that the total mass of chips, the groove volume and the observed optimum cutter spacing increase with increasing pre-set penetration depth. It is also found that the total mass of chips could be an alternative means to determine optimum cutter spacing. In addition, analysis of chip size distribution suggests that the mass of large chips is dominated by both cutter spacing and pre-set penetration depth. After fractal dimension analysis, we found that cutter spacing and pre-set penetration depth have negligible influence on the formation of small chips and that small chips are formed due to squeezing of cutters and surface abrasion caused by shear failure. Analysis on specific energy indicates that the observed optimum spacing/penetration ratio is 10 for the sandstone, at which, the specific energy and the maximum angle of lateral cracks are smallest. The findings in this paper contribute to better understanding of the coupled effect of cutter spacing and pre-set penetration depth on TBM performance and rock breakage, and provide some guidelines for cutter arrangement.
... The concepts mostly involve discs as the cutting tools which are applied in an undercutting fashion. 1 Apart from changing the cutting concept another possible solution to the problem is artificially reducing the strength of the rock mass prior to the mechanical excavation process. It has been clearly demonstrated how the strength of the rock mass will significantly influence the cutting performance of a road header 2,3 and also for TBMs (e.g 4,5 ). This means that artificially reducing the rock mass rating will enable the small and flexible machines to perform well also in tough conditions. ...
Article
This paper discusses the influence of pre-conditioning by microwave irradiation of granite on crack formation and subsequent mechanical cutting of granite with UCS of 210 MPa and CAI of 4.2. With the help of micro- and macroscopic analyses (CT-scans, linear cutting test rig) it will be shown how high-power microwave irradiation with 24 kW influences the structure of the rock and leads to local damage directly in the area of the beam and to global damage in the area surrounding area. The result is a pronounced network of cracks stretching out over the entire surface of the rock sample with a depth wise extension of approx. 100 mm. This artificially introduced crack network will lead to a significant reduction in required forces when cutting the material (6.04 to 4.29 and 6.26–5.22 kN for 8 and 12 mm cut spacing, respectively) and consequently also to a reduction in the specific energy consumption for the cutting process (50 down to 35 kWh/m³). Additionally the size distribution of the fragments will be changed to coarser sizes with ×50 changing from 0.97 and 2.05 to 1.51 and 2.39 mm for 8 and 12 mm cut spacing, respectively.
... Many studies have examined the influence of geological parameters on the performance of tunnel boring machines. These include Wanner andAeberli (1979), Howarth (1981), Lindqvist and Lai (1983), Sanio (1985), Bruland (2000), Barton (2000), Ribacchi and Lembo-Fazio (2005), Gong et al. (2005Gong et al. ( , 2006, Zhao et al. (2007), Yagiz (2009), Yagiz et al. (2011), Hassanpour et al. (2011), Bejari and Khademi (2013, Farrokh et al. (2012) and Macias et al. (2014). Wanner and Aeberli (1979) considered the property of joint frequency which is determined by the total joint area per unit volume of excavated rock. ...
Conference Paper
Hard rock tunnel boring has become widely used and is currently an important method employed by the tunnelling industry. The development of tunnel boring machine (TBM) technology has made the approach applicable in an increasingly wider range of rock mass conditions. Technically speaking, excavations can now be carried out in almost all rock conditions using this method, given certain economic constraints. Hard rock tunnel boring leads the interaction between the rock mass and the machine, which is a process of great complexity. The tunnelling system around the excavation process has a great relevance in the final goal of performance predictions for hard rock TBMs, which is the estimation of time and cost. Operational parameters, applied thrust and cutterhead velocity (rpm), have a significant influence during TBM excavation. On the aim of efficient tunnel boring, operational parameters should be adapted to the rock mass conditions and machine specifications. 'On-site' testing has the main purpose of evaluate machine performance under a given set of geological conditions. 'On site' testing involves the commonly used penetration test and the recently introduced ‘RPM test’ and it should be followed by detailed engineering geological mapping and rock sampling for drillability assessments. A penetration test consists of a measurement of cutterhead penetration over a given time at a variety of logged thrust levels carried out at constant cutterhead velocity while an ‘RPM test’ measures cutterhead penetration over a given period at a variety of cutterhead velocities under constant cutterhead thrust. This paper analyses the influence of the operational parameters, cutter thrust and cutterhead velocity (rpm), in hard rock tunnel boring efficiency on the basis of rock boreability and 'on-site' testing.
... The planning of tunnel projects and the consequent selection of construction methods require the effective prediction of Tunnel Boring Machine (TBM) performance, in order to make tunneling more effective and cheaper than traditional drill and blast method, by guaranteeing concurrently the same construction level of safety. During the last decades many researchers (Barton, 2000;Blindheim, 1979;Bilgin et al., 2013;Gong and Zhao, 2009;Hamidi et al., 2010;Hassanpour et al., 2011;Macias et al., 2014;Nelson and O'Rourke, 1983;Ozdemir, 1977;Rostami and Ozdemir, 1993;Sapigni et al., 2002;Tarkoy, 1975;Yagiz, 2002Yagiz, , 2006Yagiz, , 2008 have developed several methods for estimating the TBM performance, by analyzing the interaction between the rock mass features and the operating characteristics of the TBM. ...
Article
The Tunnel Boring Machine (TBM) performance prediction is fundamental both to select the most effective tunnel construction methods and to estimate the condition of excavation, in terms of time and economic costs of the infrastructure. Many researchers have developed several empirical and theoretical models, mainly based on the comparison between geological-geotechnical rock masses characteristics and TBM data. However, these models are specific-site and hardly applicable to different contexts. The aim of this work is to carry out easy models utilizable during early stage of tunnel planning and realization; for this purpose singular rock mass parameters (Uniaxial Compressive Strength, quartz content, spacing between fractures, etc.) have been related to TBM performance indices, as the Rate of Penetration (ROP) and the Field Penetration Index (FPI). In particular, this study focuses on “La Maddalena” exploratory tunnel (Tunnel Euroalpin Lyon-Turin), situated in northern Italy, where geological, geotechnical and TBM performance data have been continuously collected during tunnel construction.
... They include various input parameters such as rock strength, as well as cutter geometry and machine specifications to estimate the penetration rate. The most important and well-known models are those by Colorado School of Mines (Rostami et al., 1994;Rostami 2013, Rostami, 2016 and Norwegian model developed by NTNU in Trondheim (Bruland, 1999;Macias et al., 2014). This study is based on the CSM-model. ...
Conference Paper
Excavation of very hard intact rock by various mechanized systems is challenging and requires high cutting forces. This refers to tunneling through rock that is in excess of 200-300 MPa, which has also been considered difficult tunneling conditions by the ITA Workgroup 14 that is specialized in mechanical excavation. There are innovative concepts to improve the cuttability of hard and abrasive rocks by using pre-conditioning systems for introducing micro-fractures in the rock. This includes high-power microwave irradiation which leads to weakening of the rock by introducing micro fractures in the medium. The initial results of treating rock surface with a 24 kW microwave shows initiation of some micro-crack network and the preliminary results will be discussed in this paper. The findings will be linked to possible improvements of tunnel/shaft boring machines (TBM, SBM) performance, especially with respect to possibility of deploying a hybrid system to aid the center and gage cutters by pre-damaging the rock.
... In principle, for low degree of rock mass fracturing (i.e. high FS), the net penetration rates are mostly controlled by the intact rock properties playing the most dominant role while conversely for high degree of fracturing, the boring process and net penetration rate are mostly controlled by fracturing (Macias et al. 2014). However, the results of this study suggested that the FPI was mostly controlled by Alpha instead of FS as FS is not as important as Alpha for the employed datasets. ...
Article
Full-text available
Estimating the field penetration index (FPI) is an essential task in tunneling as the FPI is used to determine the tunnel boring machine (TBM) performance. In this study, fuzzy inference system (FIS) modelling is implemented to predict the FPI. Several models including fuzzy clustering and knowledge-based models were proposed. Data from the Queens Water Tunnel underneath Brooklyn and Queens were used to establish and validate the models. The input parameters include the rock type, uniaxial compressive strength, Brazilian tensile strength, rock brittleness (BI) of the intact rock, the angle between the plane of weakness and the TBM driven direction (Alpha), the distance between planes of weakness (FS), and the TBM cutter load. In order to evaluate the effect of the characteristics of the fractures on the FPI prediction, several models with different inputs and dataset structures were explored. The models were tested with independent datasets and performance indices used included the coefficient of determination R2, values account for (VAF), root-mean square error (RMSE) and mean absolute percentage error (MAPE). Overall, the model performance results were satisfactory with R2, VAF, RMSE and MAPE ranging between 0.79–0.92; 79.42–92.06%; 6.66–11.05; and 5.68–8.96%, respectively indicating good predictability capability. The models based on fuzzy clustering yielded higher accuracy. It was established that BI, Alpha and CL were the parameters controlling mostly the FPI. Based on that, the knowledge-based model was developed and satisfactory results were achieved as well. It was concluded that the FISs could be used to estimate the FPI values with a reliable accuracy.
... However, the applications of mechanical cutting and excavation tools (e.g., road headers and tunnel boring machines (TBMs)) are limited due to the high strength and high integrity of the hard rock. Particularly in underground deep mining, it has been clearly demonstrated that high rock strength and integrity will significantly influence the excavation performance of road headers [10] and TBMs [11,12]. Therefore, by reducing the rock strength and integrity, it would be possible that the small and flexible continuous excavation machine can perform well in hard rock underground excavation. ...
Article
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Excavation unloading is a primary stress condition for engineering rock mass in deep underground. Based on the unloading stress condition during the excavation operation, this paper employed a distinct element method (DEM) to simulate the unloading responses of intact and preflawed rock specimens. The simulation results revealed that the unloading failure strength, unloading damage thresholds, and cracking characteristics were largely dependent on the inclination angle α of the preflaws. With the increase in the flaw inclination angle, the unloading failure strength of a preflawed specimen exhibited a sigmoidal curve increasing trend, and it decreased by 5.5%-20% compared to the unloading failure strength of an intact specimen. Based on the crack accumulation in specimens, three damage thresholds were identified under unloading condition and two damage thresholds σci and σdi were found to be increased with the increase in the flaw inclination angle. Furthermore, when the flaw inclination angle was smaller, cracks were initiated around the preflaws, and there were obvious axial splitting cracks in the failure modes of preflawed specimens, while axial splitting cracks were few in the preflawed specimen with a larger flaw inclination angle and none in the intact specimen. These unloading responses indicate that inducing preflaws can reliably reduce the unloading failure strength and promote the cracking process of hard rock during an excavation unloading process. Moreover, inducing preflaws with a smaller inclination angle (e.g., vertical to the unloading direction) will be more helpful for the unloading failure and rock cracking during an excavation unloading process.
... DEM-based software programs such as UDEC (Gong et al., 2006;Gong et al., 2005) and PFC (Choi and Lee, 2014;Moon and Oh, 2012;Su and Ali Akcin, 2011) have also been widely used. Moreover, some on-site studies have been conducted to study rock cutting and TBM boring performances, such as cutter force monitoring Entacher et al., 2013), cutterhead thrust and torque analysis (Gong et al., 2007), the influence of rock mass fracturing (Macias et al., 2014), and TBM performance in mixed or highly fractured ground conditions (Steingrimsson et al., 2002). Furthermore, many innovative rock-breaking theories and methods have been proposed, such as high-pressure water jet cutting (Liu et al., 2014;Lu et al., 2013), high-power laser cutting (Ahmadi et al., 2011;Mohammadi and Patten, 2016), microwave-assisted cutting (Hartlieb et al., 2016;Zheng et al., 2017), and free face-assisted cutting (Geng et al., 2016a;Xia et al., 2017). ...
Article
This paper presents a numerical study on the rock muck transfer process of tunnel boring machines (TBMs) cutterhead. The discrete element method (DEM) is employed, and rock muck is modeled using a clump strategy that considers the geometric parameters of muck, such as gradation, shape and size. The numerical method is verified through tests conducted on a scaled cutterhead bend. The influences of the number and size of the mucking chute, muck shape, cutterhead diameter and revolutions per minute (RPM) on the ability and stability of muck transfer is investigated via numerical simulations. Results show that the muck transfer ability increases with the number, length, width, and area of the mucking chutes, but decreases with the cutterhead RPM. The muck transfer ability is strongly influenced by the muck shape, and the muck sphericity or the scrolling ability is a critical factor influencing the mucking performance of TBM cutterheads. The muck transfer stability improves significantly with the number of the mucking chutes, but no evident effect with respect to chute size. These findings may be useful to understand the muck transfer mechanism of TBMs and can be used as guidance for mucking chute design and TBM operation.
... Avunduk and Copur [14] established a nonlinear regression model of rate of penetration by several soil property parameters such as particle size distribution and natural water content. Macias et al. [15] analyzed the change rule of prediction curve of rate of penetration of a hard rock TBM under different fracturing conditions, and the fracturing coefficient was determined as an effective index of the influence of rock fracturing on tunneling performance. e single index affecting the rate of penetration was regressed by Armetti et al. [16] to analyze the influence degree of different parameters in the empirical model on the tunneling performance. ...
Article
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At present, many large-scale engineering equipment can obtain massive in-situ data at runtime. In-depth data mining is conducive to the real-time understanding of equipment operation status or recognition of service environment. This paper proposes a geological type recognition system by the analysis of in-situ data recorded during TBM tunneling to address geological information acquisition during TBM construction. Owing to high dimensionality and nonlinear coupling between parameters of TBM in-situ data, the dimensionality reduction feature engineering and machine learning methods are introduced into TBM in-situ data analysis. The chi-square test is used to screen for sensitive features due to the disobedience to common distributions of TBM parameters. Considering complex relationships, ANN, SVM, KNN, and CART algorithms are used to construct a geology recognition classifier. A case study of a subway tunnel project constructed using an earth pressure balance tunnel boring machine (EPB-TBM) in China is used to verify the effectiveness of the proposed geological recognition method. The result shows that the recognition accuracy gradually increases to a stable level with the increase of input features, and the accuracy of all algorithms is higher than 97%. Seven features are considered as the best selection strategy among SVM, KNN, and ANN, while feature selection is an inherent part of the CART method which shows a good recognition performance. This work provides an intelligent path for obtaining geological information for underground excavation TBM projects and a possibility for solving the problem of engineering recognition of more complex geological conditions.
... To overcome the shortcomings of theoretical methods, recently, a large number of empirical models were established on the bases of the correlation between TBM performance indices, such as rate of penetration, field penetration rate and boreabiltiy index, and the properties of the jointed rock mass in the field, including number of joint set, orientation of joints, and spacing between joints and joint frequency (Barton 2000;Hassanpour et al. 2011;Macias et al. 2014;Rostami 2016;Yagiz 2008Yagiz , 2017. For example, Farmer and Glossop (1980), Hamidi et al. (2010), and Hughes (1986) found that the correlation between uniaxial compressive strength of the rock and TBM performance is exponential. ...
... In recent times, with the development of numerical analysis and computer science, researchers have extensively studied rock mass classification and stability evaluation approaches: fuzzy analytic hierarchy process [12], artificial neural networks (ANNs) [13,14], distance discriminant analysis [15,16], set pair analysis [17], and so on. e stability of surrounding rocks is determined by many factors including geological conditions, exploitation factors, rock properties, and hydrogeological conditions [18][19][20][21][22][23][24]. ese factors have mutual effects and complicated nonlinear relationships. ...
Article
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To accurately classify the stability of surrounding rock masses, a novel method (VSV-BDA) based on virtual state variables (VSVs) and Bayesian discriminant analysis (BDA) is proposed. The factors influencing stability are mapped by an artificial neural network (ANN) capable of recognizing the model of rock mass classification, and the obtained output vector is treated as VSVs, which are verified as obeying a multinormal distribution with equal covariance matrixes by normal distribution testing and constructed statistics. The prediction variance ratio test method is introduced to determine the optimal dimension of the VSVs. The VSV-BDA model is constructed through the use of VSVs and the optimal dimension on the basis of the training samples, which are divided from the collected samples into three situations having different numbers. ANN and BDA models are also constructed based on the same training samples. The predictions by the three models for the testing samples are compared; the results show that the proposed VSV-BDA model has high prediction accuracy and can be applied in practical engineering.
... The conventional approaches usually determine site conditions with a single intact rock factor, which typically includes UCS or tensile strength [30][31][32]. However, some factors influencing the performance of TBM used in changeable ground conditions are ignored, such as RQD and joint spacing [33][34][35][36]. Therefore, many recent empirical approaches have considered numerous rock mass conditions and operational constraints to estimate machine performance, including operational torque and thrust [37,38]. ...
Article
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Evaluation of TBM performance is critical for the choice of TBM specifications and tunnel design. In the past decades, the hypothetical schemes depending on the rock fragmentation process and the experimental models up to field surveillance as well as machine performance are the two main methods. Traditional and conventional approaches for rock mass rate (RMR) prediction usually consider excessive parameters and the accuracies are far from actual values. A new RMR prediction model based on the optimized neural network (NN) is designed. To improve the prediction accuracy, this paper proposed a new self-adaptive rider optimization algorithm (SA-ROA), which applied optimization logic to train the NN by updating the weight as wave velocity (Vp), transverse wave velocity (Vs), Vp/Vs, statistics (Stat), orientation, magnitude, polarity, wave type, and metre. Finally, the RMR prediction analysis of the adopted NN-SA-ROA model is compared to the conventional and traditional classifiers with varied learning percentages: 50%, 60%, 70%, and 80% for three data sets, respectively. Subsequently, the performance of the proposed work is verified using other approaches based on error analysis. The predicted mean absolute errors (MAEs) and the mean absolute percentage errors (MAPEs) of SA-ROA are smaller than conventional and traditional schemes. The results show that the proposed method can successfully predict the actual RMR.
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The net penetration rate of hard rock tunnel boring machines (TBM) is influenced by rock mass degree of fracturing. This influence is taken into account in the NTNU prediction model by the rock mass fracturing factor (ks). ks is evaluated by geological mapping, the measurement of the orientation of fractures and the spacing of fractures and fracture type. Geological mapping is a subjective procedure. Mapping results can therefore contain considerable uncertainty. The mapping data of a tunnel mapped by three researchers were compared, and the influence of the variation in geological mapping was estimated to assess the influence of subjectivity in geological mapping. This study compares predicted net penetration rates and actual net penetration rates for TBM tunneling (from field data) and suggests mapping methods that can reduce the error related to subjectivity. The main findings of this paper are as follows: (1) variation of mapping data between individuals; (2) effect of observed variation on uncertainty in predicted net penetration rates; (3) influence of mapping methods on the difference between predicted and actual net penetration rate.
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Topological sampling, based on 1) node counting and 2) circular sampling areas, is used to measure fracture intensity in surface exposures of a layered limestone/shale sequence in north Somerset, UK. This method provides similar levels of precision as more traditional line samples, but is about 10 times quicker and allows characterization of the network topology. Georeferencing of photographs of the sample sites allows later analysis of trace lengths and orientations, and identification of joint set development. ANOVA tests support a complex interaction of within-layer, between-layer and between-location variability in fracture intensity, with the different layers showing anomalous intensity at different locations. This variation is not simply due to bed thickness, nor can it be related to any obvious compositional or textural variation between the limestone beds. These results are used to assess approaches to the spatial mapping of fracture intensity.
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Conference Paper
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Tunnel boring is shown to be a suitable technique method in hard rock tunnelling. Performance, disc cutter consumption and therefore cost are strongly influenced when using Tunnel Boring Machines (TBMs) in hard rock conditions. Furthermore, good predictions of TBM performance and cost facilitate the control of risk as well as avoiding delays and budget overruns. Good rock boreability assessments may be decisive for planning and controlling risk when extremely hard rocks are involved. An ongoing TBM project in particularly hard rock has been analyzed in terms of performances and cutter life assessments. Extensive geological back-mapping, complete rock laboratory testing and gathering of TBM data has been carried out in order to analyze and assess performance and cutter life by using the CSM, Gehring and NTNU prediction models for hard rock TBMs.
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Five universities from Austria, Germany and Switzerland, working intensively together with partners from the industry, client organisations, companies, consultants and TBM manufacturers, have combined to develop a new prognosis model for TBM advance rate and disc wear (the “ALPINE MODEL”). This article presents some new results from the project. Fundamentally, the new model is to be a development of the model from Gehring, which calculates the penetration from the ratio of disc load to uniaxial compression strength. Since this equation was derived from data collected from a limited number of projects in the 1980s, it is of great importance to widen the data base and to establish a standardised process for this purpose. For on‐site tests, the “Start‐stop‐penetration test” is considered the most efficient and suitable method. This test can be carried out with the TBM in the course of tunnelling and thus results in little delay. In addition to the recording of TBM data during the penetration test, detailed geological documentation of the face and the tunnel sides has to be undertaken, accompanied by geomechanical laboratory tests. A large number of such penetration tests have now been carried out on various tunnel projects in order to validate and improve the basic formula. Some of the first results are described in this article. Further themes include the rock mechanical parameters to be used, the influence of the primary stress conditions at the face and the abrasiveness of the rock.
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About this book This book describes the stage by stage development of a new method for predicting the penetration rate (PR) and the advance rate (AR) for tunnel boring machines based on an expanded version of the Q-value, termed QTBM. Some 145 TBM tunnels totalling about 1000 km in length were an-alysed and some simple formulae are developed from the results to esti-mate PR and AR from the QTBM value, or to back-calculate QTBM from performance data. Logging methods, empirical TBM tunnel support de-sign, and numerical verification of support are also treated in this slim but practical book on TBM tunnelling. Penetration rates as high as 10 m/hr, but occasionally as low as 0.1 m/hr, are a function both of the machine and rock mass interaction, and of the cutter force and rock strength interaction. Actual advance rates that could be as high as 5 m/hr for one day, or as low as 0.005 m/hr (while stuck for several months in a major fault zone) are quantitatively ex-plained. This book is a useful source of reference for consultants, contractors and owners of TBM tunnels, and for those involved with feasibility stud-ies, machine and support design and follow-up of tunnel progress. Among the geotechnical community, the book will be useful for geolo-gists, engineering geologists and rock mechanics engineers, and for all civil engineers who have a professional interest in TBM tunnelling.
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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.
Article
The TBM tunnelling technique initially focused on the soft rock environment. As the technique developed towards stronger machines, more powerful motors and larger cutters, hard rock TBM tunnelling became a routine task. Today, there are few ground conditions where the TBM technique is not feasible. A certain and in some cases serious limitation is, however, represented by varying ground conditions, such as dykes, faults, weakness zones or even soils/soft rock, combined with hard rock. This is commonly referred to as mixed-face conditions. Variable geological conditions may call for customised machine design, and in the development of the design, geological knowledge is crucial. An identification of scenarios that may cause a threat to the successful implementation of the TBM-method, is more important than for conventional drill and blast tunnelling, as the latter has a greater flexibility.
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Rock mass parameters including weak surfaces are the most important parameters which should be taken into account for an accurate analysis of the rock penetration by disc cutters. To date, many experimental, theoretical, and numerical simulation-based researches have been carried out on the interaction of TBM disc cutter performance and joint spacing and orientation. In this study, the simultaneous effects of joint spacing and orientation on rock indentation and fragmentation process by two TBM disc cutters are investigated by using the discrete element method (DEM). To do this, three intervals of joint spacing together with seven representative values of joint orientation are taken into consideration. Based on the results of geological site investigations, the main lithological units through which the tunnel was driven consist of sandstone, tuff, gypsum, shale, and limestone layers.
Article
This paper focuses on the analysis of the TBM performance recorded during the excavation of the Lötschberg Base Tunnel. The southern part of the tunnel was excavated by two gripper TBMs, partly through blocky rock masses at great depth. The jointed nature of the blocky rock mass posed serious problems concerning the stability of the excavation face. A detailed analysis has been carried out to obtain a relationship between the rock mass conditions and the TBM performance, using the Field Penetration Index (FPI). In blocky rock conditions, the FPI is defined as the ratio between the applied thrust force and the actual penetration rate. A database of the TBM parameters and the geological/geotechnical conditions for 160 sections along the tunnel has been established. The analysis reveals a relationship between the FPI and two rock mass parameters: the volumetric joint count (Jv) and the intact rock uniaxial compressive strength (UCS). Through a multivariate regression analysis, a prediction model for FPI in blocky rock conditions (FPIblocky) is then introduced. Finally, other TBM performance parameters such as the penetration rate, the net advance rate and the total advance rate are evaluated using FPIblocky.
Article
Various approaches for predicting penetration rate of hard rock tunnel boring machines (TBMs) have been studied by researchers since the early stages of TBM application in the 1950s. These studies resulted in the development of several penetration prediction models. For evaluation and validation of a model, it is important to test its predictive capability on new projects. A model should include parameters for machine specifications and ground conditions. The model validation process can reveal problems that an existing model may have in providing an accurate estimate for a given combination of specifications and conditions.
Article
This paper introduces the Rock Mass Excavability (RME) indicator which the authors found effective in predicting excavability by TBMs, using a quantification of TBM performance, and to provide a tool to choose the tunnel construction method. The RME is based on five parameters specifically related to rock mass behaviour and TBM characteristics. The RME has been checked with data from 22.9 km of tunnels bored with TBM. A number of statistical correlations have been established between RME and such relevant output parameters, as Average Rate of Advance (ARA).
Article
The demand for representative rock property parameters related to planning of underground excavations is increasing, as these parameters constitute fundamental input for obtaining the most reliable cost and time estimates. The Brittleness Value (S20), Sievers’ J-Value (SJ), Abrasion Value (AV) and Abrasion Value Cutter Steel (AVS) have been used extensively at NTNU/SINTEF since the 1960s in connection with drillability testing of rock samples. Nearly 3200 samples originating from projects in 50 countries have so far been tested, and the method and associated prognosis model are internationally recognised for giving reliable estimates of time and cost for tunnelling. A classification of the NTNU/SINTEF drillability indices Drilling Rate Index™ (DRI), Bit Wear Index™ (BWI) and Cutter Life Index™ (CLI) has been available since 1998, but until now no official classification has been available for the individual tests used to calculate these indices. In this paper, classifications of the NTNU/SINTEF drillability test methods Brittleness Value (S20), Sievers’ J-Value (SJ), Abrasion Value (AV) and Abrasion Value Cutter Steel (AVS) tests will be described in detail. The presented classifications of the individual tests are based on statistical analysis and evaluations of the existing test results recorded in the NTNU/SINTEF database.
Article
1. Micro hardness tests of compressed crushed rock indicate that the plastic behaviour of powder of ductile rocks, in this case a marble, resembles that of intact rock, irrespective of the deformation history of the crushed material. The inelastic deformation of such rocks under a bit can then be treated by plasticity theory. 2. The deformation properties of crushed material of granite and sandstone are of a brittle nature. Preserved grain interlocking, shape of grains (original or fractured) and degree of confinement are important factors in this respect. 3. Crushed rock powder can reconsolidate at pressures considerably lower than the contact pressure under a button of a drill or a disc cutter. Compacted crescents are then easily explained by the confined situation and the available pressure under a drill bit. 4. The inelastic zone of brittle rocks is partly kept in place by friction between tool-inelastic zone, inelastic zone-elastic matrix and by internal friction. If this friction can be reduced by some chemical agent, the inelastic zone could perhaps be squeezed out. Penetration will also increase after removal of the inelastic zone between cuts, e. g. by flushing or by some mechanical method.
Article
Karaj Water Conveyance Tunnel (KWCT) is 30-km long and has been designed for transferring 16m3/s of water from Amir-Kabir dam to northwest of Tehran. Lot No. 1 of this long tunnel, with a length of 16km, is under construction with a double shield TBM and currently about 8.7km 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 QTBM. 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. KeywordsRate of penetration-Field penetration index-TBM performance-Boreability
Article
The paper analyses the influence of rock mass quality on the performance of a double shield TBM in the excavation of a tunnel in a gneiss formation which is characterized by high strength and low fracture intensity. As full observation of the rock conditions was prevented by the use of segmental lining, a geomechanical survey of the face was performed during maintenance downtime and the observed conditions were correlated with the machine performance parameters for that same day. A statistical analysis of the data shows that penetration rate correlates well with a slightly modified RMR index (in which the influence of the water conditions and joint orientation were discounted), but the most important factor is by far the partial rating of the RMR classification related to joint spacing only. However in tunnels characterized by greater variability in rock strength and joint conditions, it could be worthwhile using the complete RMR index. Given the toughness of the rock, failure of the cutter bearings and supports were a frequent occurrence during excavation. Owing to this factor the influence of rock quality on the rate of advance was found to be weak and the correlation more scattered. The results obtained for the Varzo tunnel were compared with those relative to other tunnels in granitic rocks and found to be in good agreement. However the relationships obtained should be considered valid only for this type of rock; machine behaviour could be found to be markedly different in other rock types, even where rock material strength and joint frequency are the same.
Article
The influence of joint spacing on tunnel boring machine (TBM) penetration performance has been extensively observed at TBM site. However, the mechanism of rock mass fragmentation as function of the joint spacing has been scarcely studied. In this study, the rock indentation by a single TBM cutter is simulated by using the discrete element method (DEM), and the rock fragmentation process is highlighted. A series of two-dimensional numerical modelling with different joint spacing in a rock mass have been performed to explore the effect of joint spacing on rock fragmentation by a TBM cutter. Results show that the joint spacing can significantly influence the crack initiation and propagation, as well as the fragmentation pattern, and can hence affect the penetration rate of the TBM. Two crack initiation and propagation modes are found to fragment the rock mass due to the variation of joint spacing. The simulation results are analyzed and compared with in situ measurements.
The geological structural features of a rock mass not only affect its strength and deformability but also its cuttability and drillability. Results of wedge penetration tests and disc cutting experiments on rocks with distinctive strength anisotropy clearly show that anisotropy and discontinuities have to be fully taken into account to attain a realistic prediction of the net advance rate of a full-face tunnelling machine. Based on a simplified theoretical analysis and the experimentally proven assumption that tensile rather than shear failure is the dominant chip forming mechanism, equations for the prediction of disc cutter performance in bedded and schistose rocks are derived.
Article
The performance of tunnel boring machines (TBM) highly depends on the fragmentation efficiency of the cutters. Many geological factors can influence the rock fragmentation process. In this study, a series of two dimension numerical modeling were performed using the discrete element method (DEM) to explore the effect of joint orientation on rock fragmentation by a TBM cutter. Results show that the joint orientation can significantly influence the crack initiation and propagation as well as the fragmentation pattern, and hence affect the penetration rate of the TBM. Such observations are also noted by laboratory and site studies. It also indicates that discontinuum-based DEM has the potential in simulating rock indentation and fragmentation by TBM cutters when rock joints are taken into consideration.
Article
The penetration rate of a tunnel boring machine (TBM) depends on many factors ranging from the machine design to the geological properties. Therefore it may not be possible to capture this complex relationship in an explicit mathematical expression. In this paper, we propose an ensemble neural network (ENN) to predict TBM performance. Based on site data, a four-parameter ENN model for the prediction of the specific rock mass boreability index is constructed. Such a neural-network-based model has the advantages of taking into account the uncertainties embedded in the site data and making appropriate inferences using very limited data via the re-sampling technique. The ENN-based prediction model is compared with a non-linear regression model derived from the same four parameters. The ENN model outperforms the non-linear regression model.
Simultaneous effects of joints spacing and orientation on TBM cutting efficiency in jointed rock masses Rock mass excavability indicator: new way to selecting the optimum tunnel construction method
  • N Barton
Barton, N., 2000. TBM Tunnelling in Jointed and Fault Rock. Balkema, Rotterdam. Bejari, H., Khademi, J.H., 2012. Simultaneous effects of joints spacing and orientation on TBM cutting efficiency in jointed rock masses. Rock Mech. Rock Eng.. Bieniawski von Preinl, Z.T., Celada Tamames, B., Galera Fernandez, J.M., Alvarez Hernandez, M., 2006. Rock mass excavability indicator: new way to selecting the optimum tunnel construction method. Tunn. Undergr. Space Technol. 21 (3–4), 237.
The effect of jointed and fissured rock on the performance of tunnel boing machines
  • D F Howarth
Howarth, D.F., 1981. The effect of jointed and fissured rock on the performance of tunnel boing machines. In: Proceedings of the International Symposium on Weak Rock, Tokyo, Japan, September 1981, pp. 1069-1074.
Driftsoppfølging av TBM-prosjektet Eidi 2 Sudur (Monitoring of operations at the Eidi 2 Sudur TBM project)
  • A Palm
Palm, A., 2011. Driftsoppfølging av TBM-prosjektet Eidi 2 Sudur (Monitoring of operations at the Eidi 2 Sudur TBM project). Master's Thesis. Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
Tunnelling machine performance in jointed rock
  • H Wanner
  • U Aeberli
Wanner, H., Aeberli, U., 1979. Tunnelling machine performance in jointed rock. In: 4th Congress of the International Society for Rock Mechanics, Montreux, Switzerland, September 1979, vol. 1, pp. 573-580.
Geotechnical considerations on TBM tunnelling in rock mass
  • S Yagiz
Yagiz, S., 2009. Geotechnical considerations on TBM tunnelling in rock mass. In: 2nd International Conference on New Developments in Soil Mechanics and Geotechnical Engineering, Nicosia, North Cyprus.
  • J Macias
J. Macias et al. / Tunnelling and Underground Space Technology 44 (2014) 108–120
Factors influencing performance of hard rock tunnel boring machines Rock Engineering in Difficult Ground Conditions-Soft Rocks and Karst
  • S Yagiz
  • J Rostami
  • T Kim
  • L Ozdemir
  • C Merguerian
Yagiz, S., Rostami, J., Kim, T., Ozdemir, L., Merguerian, C., 2010. Factors influencing performance of hard rock tunnel boring machines. In: Vrkljan (Ed.), Rock Engineering in Difficult Ground Conditions-Soft Rocks and Karst. Taylor & Francis Group, London, pp. 691-700. ISBN:978-0-415-80481-3.