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This paper presents the outcomes of a sequence of three-dimensional numerical simulation models conducted in linear cutting mode, employing the LS-DYNA software. The primary objective was to scrutinize the side force values exerted on the gauge cutters. To accomplish this, an assortment of simulation models was meticulously constructed and executed, employing the Lagrange and SPG computational algorithms, along with the JHC and RHT constitutive material models. By comparing the outcomes of these models with the linear cutting experiments documented in the literature, specifically concerning the Colorado red Granite, it was determined that the SPG computational algorithm and the RHT constitutive material model proved to be the most suitable for simulating rock-cutting scenarios. Building upon the chosen computational algorithm and constitutive material model, a series of numerical models was then crafted to simulate the penetration of gauge cutters in both longitudinal and transverse orientations relative to their tips. Subsequently, the applied side forces were extracted, and a statistical model was developed to accurately predict the side forces experienced by the gauge cutters, yielding a coefficient of determination of 93%. [ABSTRACT FROM AUTHOR]

Purpose: Despite the many advantages this type of equipment offers, there are still some major drawbacks. Linear cutting machine (LCM) cannot accurately simulate the true rock-cutting process as 1. it does not account for the circular path along which tunnel boring machine (TBM) disk cutters cut the tunnel face, 2. it does not accurately model the position of a disk cutter on the cutterhead, 3. it cannot perfectly replicate the rotational speed of a TBM. To enhance the knowledge of these issues and in order to mimic the real rock-cutting process, a new lab testing equipment was developed by Hyundai Engineering and Construction. Design/methodology/approach: A new testing machine called rotary cutting machine (RCM) is designed to simulate the excavation process of hard-rock TBMs and includes features such as TBM cutterhead, RPM simulation, constant normal force mode and constant penetration rate mode. Two sets of tests were conducted on Hwandeung granite using different disk cutter sizes to analyze the cutting forces in various excavation modes. The results are analyzed using statistical analysis and dimensional analysis. A new model is generated using dimensional analysis, and its results are compared against the results of actual cases. Findings: The effectiveness of the new RCM test was demonstrated in its ability to apply various modes of excavation. Initial analysis of chip size revealed that the thickness of the chips is largely dependent on the cutter spacing. Tests with varying RPM showed that an increase in RPM results in an increase in the normal force and rolling force. The cutting coefficient (CC) demonstrated a linear correlation with penetration. The optimal specific energy is achieved at an S/p ratio of around 15. However, a slightly lower S/p ratio can also be used in the design if the cutter specifications permit. A dimensional analysis was utilized to develop a new RCM model based on the results from approximately 1200 tests. The model's applicability was demonstrated through a comparison of TBM penetration data from 26 tunnel projects globally. Results indicated that the predicted penetration rates by the RCM test model were in good agreement with actual rates for the majority of cases. However, further investigation is necessary for softer rock types, which will be conducted in the future using concrete blocks. Originality/value: The originality of the research lies in the development of Hyundai Engineering and Construction's advanced full-scale laboratory rotary cutting machine (RCM), which accurately replicates the excavation process of hard-rock tunnel boring machines (TBMs). The study provides valuable insights into cutting forces, chip size, specific energy, RPM and excavation modes, enhancing understanding and decision-making in hard-rock excavation processes. The research also presents a new RCM model validated against TBM penetration data, demonstrating its practical applicability and predictive accuracy. [ABSTRACT FROM AUTHOR]

This paper presents new methods to evaluate the conditioned soil clogging potential taking into account the slump value and consistency index of the conditioned soil with pure water. In this regard, the results of some field tests performed in two metro tunnels constructed by EPB TBMs are discussed. Major geotechnical data and soil conditioning parameters discussed in this paper include Atterberg limits, natural soil consistency index, water content, liquid injection ratio (LIR), and excavated soil workability (e.g., slump test values). In this regard, using statistical analysis, two practical formulas are developed for the evaluation of the consistency index of the conditioned soil and the slump value with the coefficients of determination of 81 and 71%, respectively. A discussion is also conducted on the clogging potential evaluation, and an improved clogging potential evaluation chart is presented with slump value iso-lines. With this, it is possible to define the required water injection and slump value for the consistency index of 0.4–0.5, which refers to low clogging potential. Based on the results, the sole information of slump is not sufficient to judge the consistency index. The new charts provided in this paper help to fine-tune the slump values corresponding to the proper range of application of EPB TBMs in various plasticity index values. [ABSTRACT FROM AUTHOR]

In this paper, important cross-section profile and layout design formulas developed for the lace design simulation of rock cutterheads (LDR) are described. In this regard, the main objectives are to optimize the cutterhead cross-section, to generate the desired combination of different cutters (single-edge, twin, multiple center cutters) in the profile of the cutterhead, to investigate how to prevent the overlap of the cutter boxes with each other and with buckets and pedestals, and to generate relationships to provide different optimized layout plans for the cutterhead with minimum off-axis forces and moments and with no boundary overlap among structural elements. The outcomes of LDR provide optimized design alternatives that enable engineers to select the best plan based on their project requirements. An example is also presented to explain the major steps followed by an application user to optimize the cross-section profile and layout plan for a micro-TBM. [ABSTRACT FROM AUTHOR]

Evaluation of optimum rock cutting performance is very important, especially at the phase of the design of a tunneling machine. In this regard, existing theoretical, laboratory, numerical, or empirical methods focus only on the optimum ratio of cutter spacing over penetration, and they need further enhancements to include various design aspects of the TBM cutterhead with respect to cut and cutter geometry parameters as well as its major layout design characteristics. Field data analysis is regarded as the most accurate and reliable method in the industry as it covers various geological conditions (which is not as easy in the laboratory or numerical simulations), and it provides new practical formulas to evaluate TBM performance. To investigate the influence of various parameters on the cutter penetration and to provide a basic guideline to optimize field cutter spacing and cutterhead layout design, an extensive field database is compiled. With the use of this database, the effects of rock type and uniaxial compressive strength on cutter penetration are investigated in various categories of cutter spacing. Major layout designs of the cutterheads utilized in various rock types and different categories of tunnel sizes are investigated for projects with relatively high performance. The results of the conducted analyses show that the maximum cutter penetration in uniaxial compressive strength values below 50 and above 150 MPa is achieved close to 90 and below 80 mm, respectively. The results of the study on the layout design characteristics of the cutterhead indicate that the evenly distributed scheme is more used with success even in softer rocks (when the rock mass condition is good). In softer rocks, the extension of the openings has to be well over 50% of the cutterhead radius to maximize its performance. In this regard, some empirical formulas are generated through statistical analysis of the data from around 300 tunnel projects to evaluate both optimum cutter spacing and optimum ratio of cutter spacing over penetration. New formulas are also provided to evaluate cutterhead thrust, torque, RPM, and power. In the end, based on the discussed issues, to optimize cutter penetration and TBM cutterhead overall performance, some procedural steps are offered. [ABSTRACT FROM AUTHOR]

Tool wear and tool life are very important issues for soft ground tunnel boring machines (TBMs) as they are directly related to the time and cost of tunneling. These issues may even become more important in planning costly interventions. In this regard, there are a few methods available to assess the tool life; however, the need for a thorough discussion and the development of new models is still highly demanded by the industry. This paper presents a summary of different methods for soft ground tool life, and tool wear evaluation. A comparative study is performed to indicate the predictability of available tool life evaluation methods based on the collected data from 23 soft ground TBM projects from around the world. Based on this database, new formulas are developed to evaluate tool life and tool wear for both primary and secondary cutting tools. The data analysis is conducted with single and multiple regression methods. The results show the equivalent quartz content and the standard penetration test are among the major influencing parameters for the evaluation of tool life of the primary cutting tools. In this regard, an estimation chart is generated for the quick evaluation of tool life for both earth pressure balance and slurry TBMs. The outcomes of this paper can be very useful in both the planning and construction stages of a TBM tunneling project where the intervention interval length and tool life/wear become critical decision-making factors for scheduling and cost evaluation and for reducing the risks of unwanted severe damage on the cutters. [ABSTRACT FROM AUTHOR]

The existing methods for estimating the advance rate of hard rock Tunnel Boring Machine (TBM) often involves estimation of the machine utilization in a direct or an indirect manner. These methods are based on empirical systems and are limited in their capacity for incorporating new machine capabilities or including many of the geological features along the tunnel. As such, these models are not used as often due to their shortcomings. The objective of this study is to offer some improvements by using a new approach for simulating all activities. The basic idea in simulation techniques is to predict the duration of different activities based on their recorded time distributions from past case histories or from the early stages of a project. A simulation model contains a series of operations, which should be repeated for a certain number of cycles. In each cycle, the model selects an anticipated duration time from time distribution curves for each activity and by using a logical relationship between activities, being parallel or in series and the possibility of activity overlaps, it assigns a duration for the whole cycle. This is then continued to finish the task at hand with required number of cycles. In this case, the cycles are the TBM going through each stroke or penetration cycle. This study includes discussion of each activity or failure of each subsystem and assigned and related duration accounts for parallel activities, and offers a distribution of cycle time, and finally estimation of tunnel completion time. A comprehensive study was conducted to evaluate the requirements for California switch final location and also the work arrangements for locomotives and trains for different scenarios. Different arrangements were programmed with Arena© simulation software using field data of a double shield TBM, which recently completed a water conveyance tunnel. The simulation results show a very good agreement with the actual values of TBM advance rate values and also show the possible variation of the time required for completion of different sections of this tunnel. The outcome of this study was to establish a framework for arranging and modeling the main time components of TBM operation. This will provide a useful tool for developing reliable estimates of machine advance rate for specific site, ground condition, and machine type. [ABSTRACT FROM AUTHOR]

Estimation of advance rate and utilization of tunnel boring machines (TBM) are some of the important steps in planning a TBM tunneling project. Estimation of the utilization factor depends on realistic analysis of downtime components. Among the different parameters influencing TBM downtime, tunnel support is the most influential factor, which can take up to 50% of the total excavation time in some cases. Although, there are some rock mass classification systems specifically developed to link ground conditions with the type and amount of support installed in TBM tunneling, the related downtime for support installation has not been studied in detail. Unit supporting time (UST) is the time required for the installation of ground support per unit length of tunnel. Support installation time (SIT) is the time required for installation of a single ground support element. In this paper, approximate ranges of UST and SIT are discussed and analyzed on the basis of recorded ground SIT from a number of TBM tunneling projects. The primary goal of this paper is to link UST with rock mass classifications that have been specifically developed to assess ground support requirements for different tunnel sections using open-type TBM. An accurate estimate of UST and SIT allows for realistic determination of the related downtime and TBM utilization rate. [ABSTRACT FROM AUTHOR]