In recent years, mechanized tunneling and using tunnel boring machines in different ground conditions has developed. Selecting the appropriate tunnel boring machine is one of the important and determinative steps in excavation advances. In this regard, according to excavation and tunnel boring machine properties, can be select the best option. In this study, in first step, criteria such as RQD index, uniaxial comprehensive strength, tensile strength, wall's instability, face instability, distance between joints, water inflow, squeezing, fault zones, karstic voids, tunnel diameter, tunnel slope and tunnel curvature radius was selected, until in next step, four proposed machine be evaluated, and the appropriate option be selected. In following, by using Fuzzy-TOPSIS method and expert's comments, appropriate machine for excavation the second part of Emamzade Hashem tunnel was selected. The results showed that, according to the above criteria, the Double Shield Universal TBM is the best selection to excavate the second part of Emamzade Hashem tunnel. Summary In this study, in first step, in order to select the appropriate tunnel boring machine among proposed machines, thirteen criterions was chosen. In next step, For the use of expert's Comments, Questionnaires was sent. After weighting to criteria, and the proposed alternatives by using the experts Comments, best option was selected. Introduction Nowadays Due to population growth, road traffics has increased. To overcome this problem, reduction in costs and decrease the journey time, tunneling and using the tunnel boring machines has increased. Selecting the appropriate tunnel boring machine can be done by using decision-making methods. In order to, the alternatives most be compared according to criteria with each other. Finally according to the decision-making method solution, the best option is selected. Methodology and Approaches In this study, for selecting the appropriate TBM, Fuzzy-TOPSIS decision-making method were used. In this method in first step after making decision matrix and weighting to criteria, Results and Conclusions According to the results, Double Shield Universal TBM selected as appropriate Option. Flexibility of machine against criteria, specially Geotechnical and geological hazards is the most important reason to achieve this result.

Summary The phenomenon of TBM jamming is one of the most hazards in full mechanized tunneling projects that should be considered at design time. This paper investigates the jamming possibility around full face excavation machine in Qom metro project. To achieve this purpose, different solution methods including empirical relations, analytical solutions and numerical modeling have been used. Since the excavation environment is continuous, to analyze the tunnel based on the numerical method, the Plaxis 3D software is used. Based on the results, in some areas, there are face instability and also the possibility of TBM jamming. It should be mentioned that the obtained results are function of the analysis method so that the calculated support pressure in numerical modellings is larger than its value in the other methods. Introduction Tunneling in weak and low resistance environments presents significant design challenges. As the resistance parameters of these media are low, the displacement analysis and the assessment of the non-elastic zone characteristics are very important, especially in areas where there are numerous high-rise buildings. Furthermore, the tunneling-induced ground displacement has a great influence on existing urban structures, and the evaluation of displacements (in the design stage) is a difficult subject, which many tunneling engineers have encountered. In these media, tunneling by TBM is an effective method to control the ground displacements. However, when a large time dependent deformation occurs around the tunnel, the ground pressure imposed on TBM shield could cause TBM jamming. Therefore, the jamming prediction in full mechanized tunneling projects is an essential part of tunnel design and machine selection. Methodology and Approaches The Qom metro project is one of important urban tunneling projects in Iran. In this project, about 10 kilometers of the entire tunnel are excavated by an earth pressure balance (EPB) shield TBM. The main purpose of this paper is to investigate the jamming possibility surrounding shield of EPB-TBM in the Qom metro project. The pressure required for the face stability was calculated using empirical, analytical and numerical methods. The numerical modeling in this study is carried out using Plaxis 3D software. Moreover, a comparison is made between the results of different methods. Finally, the effect of various parameters on the face stability and jamming possibility is evaluated via sensitivity analysis carried out in this research work. Results and Conclusions According to the results, when the ratio of overburden to tunnel diameter is more than 2, the results of the analytical and numerical methods are similar. The differences in results are due to differences in the parameters and the behavioral model used in the numerical modeling and analytical methods. For example, in some analytical methods, for excavation medium, the elastic behavior is considered, while in three-dimensional (3D) numerical modeling, several non-elastic behaviors could be considered.

The arrangement and layout of cutting tools in the cutter head are among the most critical factors affecting the performance of the Tunnel Boring Machine (TBM). These factors directly impact the drilling operation efficiency, the TBM's useful lifespan, and the cutting tool's overall performance. In general, designing the cutting tool layout poses a multi-objective optimization challenge with non-linear constraints, resulting in computational complexity during the design process. Researchers have faced significant challenges in developing efficient computational models for designing cutting tool layouts in TBMs due to the complexities arising from the technical requirements of TBM structures and drilling engineering constraints. In this study, the primary aim is to assess the influence of different cutting tool layouts on TBM performance. To achieve this, a numerical model has been created, employing the Grey Wolf Optimization (GWO) metaheuristic algorithm to design three types of layouts: stochastic, spiral, and star. To evaluate the performance of the developed design model, a practical TBM for rock excavation was selected, and the process of designing the cutting tool layout in its cutter head was analyzed. According to the research findings, it is evident that the TBM's performance has shown remarkable improvement with all three types of cutting tool layouts: stochastic, spiral, and star, compared to the original setup. The results indicate that the TBM with a stochastic cutting tool layout outperformed the spiral and star layouts, achieving an approximately 8% reduction in the overall lateral force compared to the star layout, and a 10% reduction compared to the spiral layout. Furthermore, the stochastic layouts led to an 11% decrease in eccentric torque compared to the star layout, and a 14% decrease compared to the spiral layout. After analyzing the results and assessing the TBM's performance under the spiral and star layouts, it was evident that the TBM with the star cutting tool layout outperformed the spiral layouts. The star layout resulted in a more significant reduction, approximately 4%, in the overall lateral force of the TBM and a 2.5% decrease in the eccentric torque compared to the spiral layouts. The most crucial outcome of this research was the successful development of an efficient numerical model for designing optimal cutting tool layouts, including stochastic, spiral, and star layouts in the TBM cutter head, utilizing the GWO algorithm. The proposed model exhibited versatility, making it applicable to different operational conditions and various types of TBMs.

The implementation of infrastructure projects in the transportation industry is always considered one of the most expensive projects for the development of countries, and tunnels also account for a significant portion of these costs. One of the important issues in tunneling is the behavior that the earth exhibits in squeezing conditions. In the squeezing ground, the stones move into the tunnel and cause problems in the maintenance and continuation of the tunnel construction. For tunneling in squeezing rock, it is necessary to first know the type of phenomenon and its intensity carefully and then design the required drilling method and maintenance system according to the available information. This article aims to identify the squeezing tunnel and its behavior through numerical analysis and modeling of the Chamshir tunnel. According to the conditions of the mechanized drilling machine, including the instability of the working front, the relative flexibility of the machine in changing the drilling diameter, the supply of force propulsion, and machine extension control, the best mechanized drilling equipment should be selected, and its driving force should be determined in such a way as to prevent the TBM from getting stuck inside the tunnel.

The performance of mechanized excavation depends on the soil abrasivity and the resistance of cutting tools against wear. The wear has a negative effect on excavation machine parameters, such as penetration rate, and reduces the machine's efficiency. Worn tools require replacement, which interrupts the project and incurs high maintenance costs. For this reason, many efforts have been made to understand the interaction between soil and cutting tools. Various wear-measuring devices have been designed and built to measure soil abrasivity and cutting tool wear. In this research, to study the mechanism of tunnel excavation in the laboratory, a tunnel boring machine laboratory simulator was designed and built, and the effect of the operating parameters of the excavation machine on the average wear of cutting tools was studied. The features of this machine are its horizontal excavation, the low rotation speed of the cutterhead, continuous contact of the cutters with fresh soil during the test, and continuous injection of materials with a specific injection pressure during the test. Using the granulation of soil prepared from Tabriz metro line 2 in three moisture content of zero, 7, and 13%, the effect of the rotation speed of the cutterhead, rotation time, and penetration rate on the wear of cutting tools was studied. The investigations showed that with the increase in the rotation speed of the cutterhead, the average wear increases. Also, the increasing rotation time has caused more friction between the cutting tools and the cutterhead with the soil, and the wear has increased. The wear decreased with the increase in the penetration rate, despite the increase in the intensity of the conflict between the soil particles and the cutting tools. The results obtained from this research by using a tunnel boring machine laboratory simulator are in good agreement with previous studies.

Qomroud Tunnel with the length of 35.7 kilometers is one of the greatest national projects. EPB type tunneling machine has been selected for boring of lot 1 with the length of 11+311 kilometers. Prediction of utilization factor is very important for prediction of advance rate and afterward project complete time and costs. Utilization factor is defined as the machine boring time net divided by the available total time of each geology unit. This factor is depends on geology conditions, machine type, back up installations, project management and finally worker’s experience. The NTH and CSM methods are the most important methods that are used for prediction of utilization factor in countries. In this article a method which has the closer values to actual utilization factors has been presented for achievement to utilization factors. Then TBM utilization factor has been predicted for each tunnel path geology unit by three ways and has been compared with actual data for 4570 meter length which has been bored and then tunnel boring accomplishment time has been predicted. The goal of the article is representation of a model for so accurate estimation of utilization factors and finally correct decision of project scheduling and the income and cost prediction in TBM excavation projects.

A tunnel boring machine (EPB Hard Rock type) was used to construct the Azad Water Transfer Tunnel. The adverse geotechnical conditions in a fault zone presented special risks to the machine operation. These risks were also experienced in the Bazideraz Tunnel (machine jamming and stopping, conditioning of excavated materials). In this study, various research methods were used to investigate the operation and improvement of the Azad Tunnel Machine equipment, including: Reviewing previous technical experiences through research texts and literature (related to the Bazideraz Tunnel), examining geological observations during the machine's advance, analyzing machine deflection measurement data, conducting excavation material grading tests, analyzing operating parameters recorded in the machine's data logger system (Thrust, Penetration rate, Face pressure), and documenting remedial solutions. The results show that the implementation strategies for guiding the excavation machine in the fault zone (using additional hydraulic cylinders, installing stage high-pressure pumps, Changing the excavation mode from closed mode to semi-open and open mode, etc.) have been correctly adopted based on technical thinking and engineering judgments. The results of this study can be useful in transferring technical experiences about the guidance method and improvement of TBM and prevent the stopping of TBM.

Mechanized tunneling in hard rock is associated with various challenges and risks, one of which is the penetration rate of Tunnel Boring Machine and the occurrence of grinding and chipping in various conditions. When the strength of the rock is high and the amount of jointing is low, the penetration rate of the machine is reduced and instead of forming rock chips in the tunnel face. In these conditions, which is called grinding, tunneling is associated with wear and high consumption of cutting tools as well as a severe reduction in the efficiency of excavation operations. In this paper, the boundary between grinding and chipping processes is investigated and a criterion for determining the minimum normal force in different geomechanical conditions required to create chipping condition is presented. For this purpose, data related to Kerman Water Tunnel and Southern extension of Tehran Metro Line 6 tunnel are used. In this regard, by comparing the normal forces on the cutting tools and the resulting penetration rate, the threshold for changing conditions from the grinding phenomenon to chipping is determined. The results show that the amount of normal force required to be applied by the disc cutter to the rock mass to excavate under the chipping conditions for rocks with medium, high and very high uniaxial compressive strength are equal to 130, 210 and 225 kN, respectively. Moreover, by examining the data of Metro Line 6, the role of joints in providing the conditions for chips formation was investigated and the result showed that the boundary between grinding and chipping for medium strength rocks can be at RQD=75%. It was also found that with the penetration rate exceeding a certain threshold, a slight increase in normal force causes a significant increase in the penetration rate, which increases efficiency and reduces operating costs.

key factor in the successful application of a tunnel boring machine (TBM) in tunneling is the ability to develop accurate penetration rate estimates for determining project schedule and costs. Thus establishing a relationship between rock properties and TBM penetration rate can be very helpful in estimation of this vital parameter. However, this parameter cannot be simply predicted since there are nonlinear and unknown relationships between rock properties and TBM penetration rate. Relevance vector regression (RVR) is one of the robust artificial intelligence algorithms proved to be very successful in recognition of relationships between input and output parameters. The aim of this paper is to show the application of RVR in prediction of TBM performance. The model was applied to available data given in open source literatures. In this model, uniaxial compressive strengths of the rock (UCS), the distance between planes of weakness in the rock mass (DPW) and rock quality designation (RQD) were utilized as the input parameters, while the measured TBM penetration rates was the output parameter. The performances of the proposed predictive model was examined according to two performance indices, i. e., coefficient of determination (R2) and mean square error (MSE). The obtained results of this study indicated that the RVR is a reliable method to predict penetration rate with a higher degree of accuracy.

Tunnel Boring Machines (TBM) is among the most important machines for tunnel excavation purposes. Evaluation of the performance of these machines for excavation is of special importance due to the high cost of these machines. Prediction of the penetration rate is one of the indicators in evaluation of TBMs. There are various methods and equations for predicting the penetration rate, which are based on parameters related to the rock mass and specifications of the machine, and each of them has its own particular characteristics. Multivariable linear regressions, artificial neural networks, and adaptive neuro-fuzzy inference systems are among the highly efficient modeling and data pattern recognition methods. In this research, some equations have been proposed for predicting the penetration rate in Zagros I Tunnel by employing multivariable linear regression method and by considering the key parameters of the rock mass and the specifications of the TBM; the best equation was selected according to the results of statistical analysis. For verifying the validity of this equation, the penetration rate was calculated at certain parts of Ghomrood Tunnel. In comparison with the real values and results of other models, the outcomes of calculations indicated that predicted values for the penetration rate are of acceptable accuracy.