Shield Tunnel Boring Machine Research Articles

A monocular vision and inclinometer combined system for 6DOF measurement of double shield TBM

In order to detect the 6-DOF motions between the two shields of double shield tunnel boring machine (TBM) during excavating process, this paper presents a 6-DOF measurement system combining monocular vision and inclinometer sensors. This technique extends the traditional monocular vision method by adding two inclinometer sensors on the camera and the feature point target of the monocular vision system respectively. Combined measurement model of the system is established and a weighted optimization solution is presented with linear estimation as iterative initial value. A calibration method for the rotation between the inclinometer and the feature point target is elaborated. Through Monte Carlo simulations and comparison experiments of spatial coordinate measurement with total station, the feasibility of the measurement model is validated and the measurement accuracy of the system is evaluated. Compared with the pure monocular vision method, the proposed method greatly improves the measurement accuracy.

막장전방 예측기법에 근거한 TBM 터널의 리스크 관리 시스템 개발 및 현장적용

ABSTRACT: When utilizing a Tunnel Boring Machine (TBM) for tunnelling work, unexpected ground conditions can be encountered that are not predicted in the design stage. These include fractured zones or mixed ground conditions that are likely to reduce the stability of TBM excavation, and result in considerable economic losses such as construction delays or increases in costs. Minimizing these potential risks during tunnel construction is therefore a crucial issue in any mechanized tunneling project. This paper proposed the potential risk events that may occur due to risky ground cond itions. A resistivity survey is utilized to predict the risky ground conditions ahead of the tunnel face during construction. The potential risk even ts are then evaluated based on their occurrence probability and impact. A TBM risk management system that can suggest proper solution methods (measures) for potential risk events is also developed. Multi-Criterion Decision Making (MCDM) is utilized to determine the optimal solution method (optimal measure) to handle risk events. Lastly, an actual construction site, at which there was a risk event during Earth Pressure-Balance (EPB) Shield TBM construction, is analyzed to verify the efficacy of the proposed system.Keywords: TBM, Risk management, Ahead of tunnel face, Risky ground prediction, MCDM

Risk analysis using fault-tree analysis (FTA) and analytic hierarchy process (AHP) applicable to shield TBM tunnels

In this paper, the potential risk of undesirable events occurring during tunneling with application of a shield tunnel boring machine (TBM) method is discussed along with the risk analysis which can systematically assess overall risk levels. Potential risks and typical scenarios pertaining to shield TBM tunnels have been investigated based on previous case histories and correspondence with experts. The relevant risks from undesirable events were categorized into four groups: cutter-related malfunction, machine blockage or hold-up, mucking problems that hinder transporting excavated materials, and segment defects. A fault-tree set was constructed by grouping risk factors (or causes) into geological, design and construction/management factors. Risk analysis was performed by adopting fault-tree analysis (FTA) and an analytic hierarchy process (AHP) with consideration of the probability and impact of the risks. In addition, the proposed method was reliably validated by comparison with field observation, and thus indicates its applicability to risk management for shield TBM tunneling.

A probabilistic analysis of subsoil parameters uncertainty impacts on tunnel-induced ground movements with a back-analysis study

In this paper a probabilistic-based analysis is presented for evaluating the influences of subsoil parameter uncertainties on tunnel-induced ground movements in mechanized tunneling. The procedures of the tunneling process using Slurry Shield Tunnel Boring Machine are numerically modeled and simulated by utilizing a finite element code. To keep the computational cost of the presented simulation model low, an efficient and reliable surrogate modeling technique is used to substitute the original simulation model. The input parameter uncertainties are mathematically represented by adequately chosen probability density functions within their extreme lower and upper bounds. Subsequently, a variance-based global sensitivity analysis is conducted for quantifying the impact of each uncertain parameter on different system responses that are considered in this study. Afterwards, the propagation of parameter uncertainties are evaluated by performing a Monte Carlo-based simulation using the computationally inexpensive surrogate model. At this stage, the variations of system responses, which result from input parameters propagating uncertainties, are compared with predetermined threshold values and, based on that, failure criteria of the tunneling system are defined as well as probabilistically quantified. In a last step, a Bayesian updating procedure is employed for reducing subsoil parameter uncertainties by utilizing recorded synthetic measurements.

Experimental investigation of reinforced concrete and hybrid fibre reinforced concrete shield tunnel segments subjected to elevated temperature

This paper presents a comprehensive experimental study on the comparative behaviour of the reinforced concrete (RC) and the hybrid fibre reinforced concrete (HFRC) shield TBM (Tunnel Boring Machine) tunnel lining segments exposed to fire. The tests were conducted using a newly developed test facility, which is capable of accommodating different mechanical loading and boundary conditions under different fire scenarios. Six RC segments and six HFRC segments were tested to the standard Eurocode HC (Hydrocarbon) curve, while two reference specimens, one for each type, were tested in ambient environment to provide benchmark data. Apart from the spalling resistance, the fire effects on the structural behaviour were investigated under different boundary conditions at the segment ends, including free sliding (no horizontal constraint), total horizontal restraint and controlled horizontal reaction. The vertical load capacities were investigated for both under-fire and post-fire scenarios. The experimental results revealed excellent spalling resistance in the HFRC segments under thermo-mechanical loading, while the RC segments exhibited better structural performance. A combination of RC design (with flexural reinforcement) and the use of hybrid fibres is deemed to be effective in providing good spalling resistance while at the same time ensuring a robust structural behaviour.

Advance rate simulation for hard rock TBMs

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.

Analysis on the behavior of shield TBM cable tunnel: The effect of the distance of backfill grout injection from the end of skin plate

최근, tunnel boring machine (TBM)을 이용한 도심지 지중 전력구 터널 건설이 증가하고 있다. 쉴드 TBM을 이용한 기계화 터널 굴착 공법은 재래식 공법에 비해 지반침하를 최소화 하고 발파에 의한 진동을 줄일 수 있는 장점이 있다. 국내에서는 earth pressure balance(EPB) 쉴드 TBM이 주로 사용되고 있다. 그러나 전력구 터널 굴착을 위한 쉴드 TBM 공법이 증가함에도 불구하고, 전력구 쉴드 TBM 터널의 거동 분석에 관한 연구는 미비한 실정이다. 본 연구에서는 후방주입 거리에 따른 전력구 쉴드 TBM 터널의 거동 특성을 분석하고, 굴착면 지반 손실과 후방주입 거리와의 상관관계를 도출하고자 한다. 쉴드 TBM을 이용한 터널 굴착은 3D FEM을 이용하여 시뮬레이션 하였다. 뒷채움 그라우트가 설치되는 거리의 변화에 따른 축력, 전단력, 휨 모멘트와 같은 단면력을 검토하고 지표면에서의 연직 변위를 분석하였다. 또한, 유한요소해석으로 얻어진 결과와 안정성 분석에 기초하여, 지반과 터널 구조물의 안정성을 확보할 수 있는 뒷채움재 주입시기를 결정할 수 있다. Recently, tunnelling with TBM is getting popular for the construction of cable tunnel in urban area. Mechanized tunnelling method using shield TBM has various advantages such as minimization of ground settlement and prevention of vibration induced by blasting that should be accompanied by conventional tunnelling. In Korea, earth pressure balance (EPB) type shield TBM has been mainly used. Despite the popularity of EPB shield TBM for cable tunnel construction, study on the mechanical behavior of cable tunnel driven by shield TBM is insufficient. Especially, the effect of backfill grout injection on the behavior of cable tunnel driven by shield TBM is investigated in this study. Tunnelling with shield TBM is simulated using 3D FEM. The distance of backfill grout injection from the end of shield skin varies. Sectional forces such as axial force, shear force and bending moment are monitored. Vertical displacement at the ground surface is measured. Futhermore, the relation between volume loss and the distance of backfill grout injection from the end of skin plate is derived. Based on the stability analysis with the results obtained from the numerical analysis, the most appropriate injection distance can be obtained.

Evaluation of waterproof and durability of hydrophilic waterstop

최근 국내에서는 쉴드 TBM (Tunnel Boring Machine)을 이용한 터널 굴착에 대한 관심이 크게 증가하고 있다. 쉴드 TBM 터널은 비배수 터널로써 세그먼트 이음부에서 누수가 발생할 경우에는 터널의 사용성 및 안정성에 문제가 될 수 있다. 본 연구에서는 첫째로 쉴드 TBM 터널의 세그먼트 시공 시 시공오차 및 세그먼트 과다변형에 의한 수팽창 지수재의 방수 성능 변화를 알아보았고, 두 번째로 지하수와 해수에 있을 수 있는 황산염과 염화물에 의한 수팽창 지수재의 내구성 저하를 알아보았다. 시험결과, 체결각 불합치가 <TEX>$2^{\circ}$</TEX>이상으로 시공 오차가 발생한 경우에는 수팽창 지수재의 차수 능력을 기대하기는 어려운 것으로 판단된다. 또한 수팽창 지수재가 황산마그네슘 용액에 장시간 노출될 경우에는 지수재의 내구 성능에 문제가 있을 수 있을 것으로 판단된다. The interest in the use of shield TBM (Tunnel Boring Machine) on the tunnel excavation has been increased rapidly in Korea. The shield TBM tunnel is generally designed as non-drainage tunnel. Consequently, if water leakage through the segment joints happens, big problems on the usage and stability of tunnel can be occurred. In this study, the variation of waterproof capacity of hydrophilic waterstop by the construction error and excessive displacement of segment was studied firstly. Secondly, the decrease of durability of hydrophilic waterstop by the sulphate and chloride contained in the groundwater and seawater was investigated. The results showed that if the angle discordance at the segment joints is beyond the 2 degree, the proper waterproof capacity of hydrophilic waterstop can not be guaranteed. In addition, if the hydrophilic rubber waterstop is exposed to the sulphate for a while, the proper durability of hydrophilic waterstop can not be expected.

Study on Linear Vibration Model of Shield TBM Cutterhead Driving System

In this paper, a general linear time-varying multiple-axis (LTVMA) vibration model of shield tunnel boring machine (TBM) cutterhead driving system is established. The corresponding multiple inputs and multiple outputs (MIMO) state-space model is also presented. The linear vibration model is analysed, and the vibration-torque transfer function matrix and the vibration-torque static gain matrix are obtained. The linear vibration model is simulated, and the physical parameters&#39; effects on the vibration response are investigated. A preliminary approach is proposed to reduce vibration by increasing motor rotor inertia and viscous damped. The LTVMA vibration model provides a solid foundation for fault detection and diagnosis (FDD), as long as the health monitoring of cutterhead driving system.

Full-scale testing and modeling of the mechanical behavior of shield TBM tunnel joints

For shield TBM (Tunnel Boring Machine) tunnel lining, the segment joint is the most critical component for determining the mechanical response of the complete lining ring. To investigate the mechanical behavior of the segment joint in a water conveyance tunnel, which is different from the vehicle tunnel because of the external loads and the high internal water pressure during the tunnel's service life, full-scale joint tests were conducted. The main advantage of the joint tests over previous ones was the definiteness of the loads applied to the joints using a unique testing facility and the acquisition of the mechanical behavior of actual joints. Furthermore, based on the test results and the theoretical analysis, a mechanical model of segment joints has been proposed, which consists of all important influencing factors, including the elastic-plastic behavior of concrete, the pre-tightening force of the bolts and the deformations of all joint components, i.e., concrete blocks, bolts and cast iron panels. Finally, the proposed mechanical model of segment joints has been verified by the aforementioned full-scale joint tests.

Research on Dynamic Models and Performances of Shield Tunnel Boring Machine Cutterhead Driving System

A general nonlinear time-varying (NLTV) dynamic model and linear time-varying (LTV) dynamic model are presented for shield tunnel boring machine (TBM) cutterhead driving system, respectively. Different gear backlashes and mesh damped and transmission errors are considered in the NLTV dynamic model. The corresponding multiple-input and multiple-output (MIMO) state space models are also presented. Through analyzing the linear dynamic model, the optimal reducer ratio (ORR) and optimal transmission ratio (OTR) are obtained for the shield TBM cutterhead driving system, respectively. The NLTV and LTV dynamic models are numerically simulated, and the effects of physical parameters under various conditions of NLTV dynamic model are analyzed. Physical parameters such as the load torque, gear backlash and transmission error, gear mesh stiffness and damped, pinions inertia and damped, large gear inertia and damped, and motor rotor inertia and damped are investigated in detail to analyze their effects on dynamic response and performances of the shield TBM cutterhead driving system. Some preliminary approaches are proposed to improve dynamic performances of the cutterhead driving system, and dynamic models will provide a foundation for shield TBM cutterhead driving system's cutterhead fault diagnosis, motion control, and torque synchronous control.

Behavior of reinforced concrete and steel fiber reinforced concrete shield TBM tunnel linings exposed to high temperatures

This paper presents comprehensive experimental test results on the behavior of the reinforced concrete (RC) and the steel fiber reinforced concrete (SFRC) shield TBM (Tunnel Boring Machine) tunnel lining segments and the lining rings exposed to a HC (Hydrocarbon) curve. The experimental results indicate that the nonlinear nonuniform temperature distribution within the concrete linings causes significant nonuniform thermal expansion and material property degradation. The initial loads exert significant effects on the behavior of the lining segments, whose performance was remarkably deteriorated in the fire. The coupled thermal–mechanical effects, induced by the nonuniform thermal expansion, the deterioration of material properties and the interaction between adjacent member segments, lead to considerable deformations of the lining rings, dynamic internal force redistribution and reduction of load bearing capacity. The lining joints play a critical role upon the behavior and the failure pattern of the lining rings. Based on our test results, the RC linings perform better than the SFRC linings under intensive tunnel fire. Other notable, new observations and behavior are also presented in this work.

Full-scale fire tests of RC metro shield TBM tunnel linings

This paper presents the full-scale experimental test results of actual RC (reinforced concrete) metro shield TBM (tunnel boring machine) tunnel linings that are exposed to a standard ISO834 curve with 45min and 90min heating durations. The purpose of this work is to investigate fire damage to the actual RC metro shield TBM tunnel linings and to develop a feasible method to improve the fire safety of existing metro shield TBM tunnel linings. The experimental test results indicate that severe concrete explosive spalling as well as property deterioration occurs under high temperatures. Because of coupled thermo-mechanical actions, the opening angles and gaps of the tunnel lining joints significantly increase. Due to deterioration in the elastic modulus and the strength of the joint bolt induced by high temperatures, the flexural stiffness of the tunnel lining joints notably deteriorates as well. The rubber waterstop almost remains intact during the fire tests, but the flexible gasket close to the heating surface is severely damaged by high temperatures. The experimental test outcomes also reveal that the newly developed filling material performs well under high temperatures, and it greatly decreases the temperature of the joint bolt and the rubber waterstop.

Artificial neural network application for the prediction of ground surface movements induced by shield tunnelling

This paper presents a methodology to correlate ground surface movements and tunnel boring machine (TBM) operation parameters. Two approaches are proposed and evaluated based on a case study of a shallow tunnel in a dense urban area. The first approach is based on a least square approximation and the second one uses an artificial neural network model. Data analysed were selected from the excavation of the subway line B tunnel in Toulouse, France, which was performed mainly by a shield TBM. Ground movements measured on the 4.7 km long contract 2 are reproduced with reasonable agreement by each of the two approaches. The amount of data (in particular for TBM operation parameters), the rather small amplitude of measured movements (a few millimetres), and the accuracy of these measurements (designed for routine construction management) make it necessary to create a pre-processing technique for the data, and a step-by-step improvement of approaches used. An elimination procedure is proposed to identify the most influential operation parameters and a sensitivity analysis shows their respective effect on ground movements.

Correlation of tunnel convergence with TBM operational parameters and chip size in the Ghomroud tunnel, Iran

Evaluating the impact of rock mass properties on a tunneling operation is crucial, especially when using a tunnel boring machine (TBM). It is an integral part of machine selection and performance prediction in the design and bidding stage. Monitoring and analysis of ground conditions during the construction is also essential to allow the operator to take precautionary measures in adverse geological conditions. This involves adjusting TBM operational parameters such as machine thrust and penetration to avoid potential problems caused by face collapse or excessive convergence and subsequent machine seizure that can cause long delays. Tunnel wall convergence is a function of rock mass characteristics, in situ stresses, size of excavation, and rate of penetration (ROP). It is one of the main factors in determining the use of shielded machines in deep rock tunnel projects. The case study of the Ghomroud water conveyance tunnel project, under construction by a double shield TBM, is used to examine the effect of rock mass parameters on tunnel convergence and hence on the need for over excavation and shield lubrication to avoid problems such as shield seizure. Results of a preliminary analysis of field observations show that the amount of the tunnel convergence can have a direct relationship with the percentage of powder and large rock fragments in the muck. In addition, tunnel convergence has shown a strong relationship with the TBM thrust/torque and rate of penetration (ROP). These relationships have been examined and the results of the analysis as well as the resulting formulas will be explained in this paper.