NATM Tunnel Research Articles

Tracking of horizontal alignment of the long and large diameter uncharged hole in NATM tunnel

The long and large diameter uncharged hole boring (LLB) method is a cut blasting method that minimizes blast-induced vibrations by creating long and large diameter uncharged holes at the excavation face of tunnels prior to tunnel excavation. Drilling in this method typically uses a 50 m long with a 382 mm diameter hammer bit in the horizontal direction at the tunnel face. However, the significant weight and uni-directional rotation of the rod head, as well as variables such as geological characteristics, machine conditions, and inexperienced operators result in significant deviation from the target borehole alignment that hinders the vibration-dampening effect of the uncharged holes. Furthermore, since there is no method to verify the alignment of the boreholes until main tunnel construction, borehole misalignment is often not discovered until weeks after construction, which requires tunnel construction to cease until the equipment can be remobilized and an additional borehole be created, causing significant delays and increased costs for the entire tunnel project. In this study, the borehole alignment tracking and ground exploration system (BGS) is developed to predict and monitor the quality and alignment of boreholes for cut blasting methods such as the LLB methods immediately after boring. The BGS was subsequently tested at a subway construction site to evaluate its performance in the field. The measurements yielded by the BGS were compared with manually measured boring positions at every 5 m along the borehole. Although the BGS showed a maximum deviation of approximately 12% at a local point where the hole surface was relatively rough, the accuracy for the final boring position was approximately 97%, demonstrating excellent precision of the alignment tracking system. The BGS demonstrates excellent performance in predicting ground conditions and the boring quality of a cut hole immediately after drilling, and shows promise in various other applications for monitoring borehole alignment.

Umfahrung Weyer – Tunnelbau im Lockergestein unter Bebauung

AbstractThe small town of Weyer is located in Upper Austria on the B121 Weyerer Straße. The B121 leads through the historic market square of Weyer, which is characterised by confusing bottlenecks that can only be passed in one lane. For decades, these bottlenecks have caused congestion, mainly due to heavy traffic. For residents, the burden of air pollution and noise is high. The roads department of the Upper Austrian Government has been planning the construction of a bypass for many years. Construction finally started in the summer of 2022. The Weyer bypass construction lot is 1.2 km long and includes the construction of two NATM tunnels, a vertical escape shaft, a bridge over the river Dürnbach, two roundabouts, and one traffic junction. The tunnel construction works are carried out in urban areas, in loose material with little overburden and partly under existing buildings. These boundary conditions make the project a challenge for all involved at every stage.

Experiment and Application of NATM Tunnel Deformation Monitoring Based on 3D Laser Scanning

In recent years, 3D laser scanning technology has been applied to tunnel engineering. Although more intelligent than traditional measurement technology, it is still challenging to estimate the real-time deformation of NATM tunnel excavation from laser detection and ranging point clouds. To further improve the measurement accuracy of 3D laser scanning technology in the tunnel construction process, this paper proposes an improved Kriging filtering algorithm. Considering the spatial correlation of the described object, the optimization method of point cloud grid filtering is studied. By analyzing the full-space deformation field of the tunnel lining, the deformation information of the measuring points on the surface of the tunnel lining is extracted. Based on the actual project, through the on-site monitoring comparison test, the three-dimensional laser point cloud data are grid processed and analyzed, and the deformation data obtained from the test are compared with the data measured by traditional methods. The experimental results show that the Kriging filtering algorithm can not only efficiently identify and extract the tunnel profile visualization data but also efficiently and accurately obtain the tunnel deformation. The measurement results obtained by using the proposed technology are in good agreement with those obtained by using traditional monitoring methods. Therefore, tunnel deformation monitoring based on 3D laser scanning technology can better reflect the evolution of the tunnel full-space deformation field under certain environmental conditions and can provide an effective safety warning for tunnel construction.

Performance of Flowable Concrete for Application in Underground Structures -NATM Tunnel and Station Box of Mumbai Metro Project

Abstract: High-performance flowable concrete offers special combinations of performance, uniformity, and consistency requirements that cannot be possible by traditional normal slump concrete. It is an advanced concrete than traditional concrete with high workability without segregation, bleeding and it is suitable for placing in structures with congested reinforcement of structure, long distance pumping concrete-like inside NATM tunnel, cross passages, and underground station box concrete structures. Flowable concrete can be flow itself but does not have the self-compacting capability. Flowable concrete required vibration to ease flow to reach each corner of formwork and compaction for achieving a smooth surface finish after deshuttering. Mix proportion of flowable concrete must ensure a good balance between deformability and stability. The behavior of concrete can be affected by the characteristics of selected ingredients in concrete and the mix proportions. It becomes necessary to evolve a procedure for mix design of flowable concrete. The paper presents an experimental procedure for the mix design of flowable concrete for grade M40 and implementation of the same mix at the cast in situ Base slab, Roof slab Rcc walls for underground metro stations, NATM tunnel & cross passages in Mumbai Metro Project, package -UGC-07. The test results for acceptance characteristics of M40 grade flowable concrete such as flow table test, compressive strength at the ages of 7, 28, and 56 days determined, and results are included here. Successful production of temperature control flowable concrete from batching plant, transportation, placement procedures, and proper planning of handling and execution of flowable concrete at the site are presented in this article.

Appropriate Selection of Materials for Making Durable Self Compacting Concrete for Using in Underground Structures

Abstract: Selecting appropriate and suitable of materials plays an important role in concrete mix design to meet the general requirements of European guidelines for self-compacting concrete and to ensure a balance between deformability and stability. The type of selected materials and the ratios of concrete ingredients can be affected by the fresh and hardened properties of the concrete. In the contract agreement of the Mumbai Metro underground project, the technical specifications clearly state the values of limits set for achieving the durability parameters for the life of 120 years of the structure. According to the requirement of the site conditions Self-compacting concrete was designed with available material, special material like Ultra GGBS- Alccofine 1203 and crystalline waterproofing admixture. Self-compacting concrete is superior concrete than the traditional concrete with high workability, no segregation, no bleeding, and it is also suitable for use in structures with long-distance pumping in the instant case i.e., more than 120-meter length in Underground NATM tunnels, cross-passages, and the concrete structure of the underground metro station box. The paper presents a comparison between concrete mix designs and their achieved test parameters suitable for the contract specification of Mumbai metro underground project

Application of 3D laser scanning on NATM tunnel deformation measurement during construction

Application of 3D laser scanning on NATM tunnel deformation measurement during construction

Comparison of NATM and Traditional Tunneling Methods in Large-Section Tunnels (A Case Study: Tunnel-3 of the Main Pataveh-Dehdasht Road)

Comparison of NATM and Traditional Tunneling Methods in Large-Section Tunnels (A Case Study: Tunnel-3 of the Main Pataveh-Dehdasht Road)

Development of Design Support Automatic Program for NATM Tunnel Based on BIM

Development of Design Support Automatic Program for NATM Tunnel Based on BIM

Multi-source data driven method for assessing the rock mass quality of a NATM tunnel face via hybrid ensemble learning models

Current assessments of rock mass quality of a NATM tunnel face are important in the practice of tunnel excavation. This study establishes a multi-source database and proposes a data driven method for the assessment. Thirteen multi-source variables describing the tunnel faces are considered as inputs, and the rock mass rating (RMR) values computed by the empirical formula are the target outputs. We adopted two meta machine learning models (classification and regression tree (CART) and multiple layers perceptron (MLP)) and two ensemble learning models (gradient boosting regression tree (GBRT)) and random forest (RF)) to capture the relationships between the inputs and outputs. The tree-structured Parzen estimator (TPE) algorithm is applied to automatically determine the optimized model hyper-parameters. The experimental results suggest that the proposed hybrid ensemble learning models (TPE-RF and TPE-GBRT) perform well at assessing rock mass quality. The feature importance ranks of the input variables are determined by a sensitivity analysis, which enhances the knowledge on assessing the rock mass quality of a tunnel face.

Stability Study Using Numerical Analysis for the Panel Method Applied to the Weathered Rock Section below the National Highway

In sections with poor ground conditions, it is difficult to apply the commonly used NATM tunnel method; thus, applications of the non-open cut tunneling method are increasing. This section is a tunnel crossing area under the national road in which the Panel method is to be applied to the section where a deeply buried layer and a loose weathered soil layer are distributed. Therefore, the stability of the upper road, the amount of settlement, and the stability of the tunnel structure were reviewed for each construction stage by using MIDAS GTX. Through the installation of measuring instruments in the tunnel area, the results of the numerical analysis were reviewed and the stability during and after construction was evaluated. Therefore, it is likely that the Panel method is an appropriate countermeasure in the downtown area and in areas with soft ground sections where the application of the general tunnel excavation method is difficult.

Alternative seismische Quellen für die Vorauserkundung im konventionellen Tunnelbau

AbstractFor seismic ahead‐of‐the‐face prediction in tunnelling, sources with known properties are usually used, which, however, are not compatible with NATM. In order to integrate geophysical exploration into conventional tunnelling, the feasibility of construction machinery for generating seismic source signals was investigated. Passive monitoring during conventional tunnelling was used to analyse the seismic signals. Different radiation characteristics of drilling, blasting and bouldering could be identified and their characteristics regarding range and spectrum of the signal could be determined. In subsequent system tests, various machines used in NATM tunnelling were examined for their suitability as sources. The sensor positioning for source signal pickup was evaluated by stroke tests and during ongoing tunnelling operations. For the registration of the waves in the rock mass, different receivers with different geometries were used to characterize the wave field emitted to the front or side of the sources. In addition, the necessary processing steps were determined in order to make these signals usable for an ahead‐of‐the‐face exploration. The results and data form a basis for further development into a practical technical solution for conventional tunnel construction.

고속철도 NATM 터널의 횡배수관 폐색과 라이닝 변상패턴 분석

고속철도 NATM 터널의 횡배수관 폐색과 라이닝 변상패턴 분석

Analysis of NATM tunneling method using CYCLONE modeling and simulation tools

The NATM or New Austrian Tunneling Method became a popular method for tunneling in Indonesia recently, since at least two strategic and huge construction projects utilized it. It is considered as a new method introduced to the Indonesian construction industry and therefore it is interesting to be studied and anticipated for the implementation. This paper discusses modeling the operation of the NATM and then simulation of the model for finding the productivity, effectiveness, and problems that may come in the implementation. The CYCLONE modeling and three simulation tools, i.e., WebCYCLONE, COST, and Symphony.Net, were utilized for this purpose. Data used for durations of tasks associated with the method were gathered from previous work in the field of different projects and literature. The results of this analysis then compared to other similar analyses but for a different project. A comparison of those two analyses was used to identify the most important tasks that will determine the performance of the method with a safety-first requirement in mind. The sensitivity analysis identified secondary resources such as a concrete wet sprayer; the shotcrete team and the formwork team are considered sensitive to improve the performance of the NATM.

Performance-based analysis of tunnels under seismic events with nonlinear features of soil mass and lining

Accurate prediction of tunnel behavior and damage states under seismic loading remains a challenge. This study carried out tunnel behavior and risk assessment using numerical dynamic analysis on a NATM tunnel. A hypoplastic model that considers intergranular strain was calibrated for a particular sand using experimental tests and numerical simulations. It then was used in numerical simulations for the surrounding soil to allow precise prediction of soil dynamic behavior at all ranges of strain. The elastic perfectly plastic model was used for the tunnel lining to detect plastic hinges under seismic motion. Similar trends for all drift-PGA curves at different surcharges and soil densities indicate that all models experienced the same phenomena at similar time intervals and represent different performance levels. The serviceability level of the tunnel is the point at which the first plastic hinge forms. The collapse prevention level produces failure mechanisms that cause instability and collapse.

Prediction of tunnel wall convergences for NATM tunnels which are excavated in weak-to-fair-quality rock masses using decision-tree technique and rock mass strength parameters

Tunnel wall convergences should be predicted before the excavation and should be determined accurately in order to ensure safe and economic tunnel excavation media. For this to be possible, rock mass behaviors in the tunnel should also be estimated prior to excavation. This could be ensured by site investigation studies, numerical models and predictive statistics. In this study, the development of convergences during a tunnel excavation in Turkey, excavated by NATM technique, was evaluated by using statistical prediction techniques for weak-to-fair-quality rock masses. For this aim, actual tunnel wall convergence data and rock mass strength parameters were used. For prediction of tunnel wall convergence, multivariable regression analysis, artificial neural networks (ANNs), classification and regression tree (CHAID) and Chi-square automatic interaction detection (C&RT) methods were used and prediction results were compared to each other in terms of superiority and practicality. For this aim, 112 tunnel sections were used for prediction model and 30 different tunnel sections were used for validation. According to the obtained statistical prediction findings, it is seen that C&RT and ANN methods provide good prediction of tunnel wall convergences. However, C&RT method was found more practical in field use when compared to ANN. The results have shown that overburden thickness is the most effective parameter on tunnel convergence when compared to Crm, Φrm, Erm, RMR and Q. However, the best way for determination of tunnel wall convergences is to use in situ measurements, but in case of the lack of in situ measurement instruments, the suggested probability-based statistical approach is proven to be very effective and practical. Ultimate convergence level for any cross section with similar geological and geotechnical parameters to those analyzed before can be predicted by using the suggested method in this study. Yet, it should be kept in mind that the findings of this study are limited with the data used in this study. Although the aim of this study is to ensure a different point of view for determination of convergences in case of lack of convergence measurements and field data, by adding up more convergence measurements and rock mass strength data to the proposed statistical method, prediction power of this method can be improved and then this method can be used as a practical tool for the prediction of tunnel convergences. Besides, the user-friendly and open-to-development structure of this study can be a very useful tool for the geotechnical engineers, engineering geologist and mining engineers, if it can be developed by more field data.

Upper-bound solutions for the face stability of a non-circular NATM tunnel in clays with a linearly increasing undrained shear strength with depth

The face stability of the NATM tunnels (the New Austrian Tunneling Method) in undrained clays with a linearly increasing strength is numerically and analytically investigated by defining two types of the safety factors F in this paper. Based on the kinematic approach of the limit analysis, a continuous velocity field for an open-face tunnel is proposed. Moreover, the calculated solutions are compared with the results obtained from the numerical simulation and other existing literatures to validate its effectivity and superiority. The stability charts for different influence factors are also provided. Finally, an improved velocity field is presented, which provides a closer result to the real situation of the face collapse.

VISIBLE TEST ON BUGHOLE GENERATION OF FLUIDITY CONCRETES FOR TUNNEL LINING

Bughole (surface air-void) is a concern for surface quality though it rarely decreases strength properties of the concrete structure. In particular, sidewall of NATM tunnel lining which generally has negative angle is a significant concern in the bughole problem. To reduce the surface imperfection of concrete, the authors examined the bughole properties and discussed on construction methods in previous investigations. The present study focuses on the relation of bughole generation and concrete viscosity. A visible test of bughole generation was conducted using high and medium fluidity concretes in addition to the conventional concrete. Bughole distribution and properties were analyzed by the image analysis which was developed in our previous study. This paper reports the effect of concrete fluidity on decrease of bugholes on concrete surface. A remarkable observation in the experimental study is that number and area-ratio of bugholes increased with concrete viscosity while large voids can be decreased by using high/medium fluidity concrete.

Application of Surface Quality Evaluation Method Based on Visual Inspection of Secondary Lining Concrete of NATM Tunnel and Approach to Surface Quality Improvement

NATMトンネルの二次覆工コンクリートは，部材が薄く，セントル型枠と地山との閉鎖空間にコンクリートを充填する施工の難しい部位である。その施工の難しさも一因となって，供用されている構造物では様々な変状や不具合が散見されている。そこで，新設の構造物では覆工コンクリートの表層部の品質を目視調査に基づいて合理的に評価する方法を用いてPDCAサイクルを回し，品質向上を図る試みがなされている。本報告では，東北地方で建設されたNATMトンネルの二次覆工コンクリートを対象として，目視調査に基づく表層品質評価の結果に関する分析および品質確保・向上に関する試みについて現場の事例について紹介する。

Designing a Two‐Floor Urban Traffic Tunnel by Using NATM Tunneling Method in Tehran Alluvium with Shallow Overburden under Modares Highway

Designing a Two‐Floor Urban Traffic Tunnel by Using NATM Tunneling Method in Tehran Alluvium with Shallow Overburden under Modares Highway

Stability analysis of shotcrete supported crown of NATM tunnels with discontinuity layout optimization

SummaryFor tunnel constructed by New Austrian Tunnelling Method, the crown is the upper part of tunnel section, constructed during excavation process and supported by shotcrete. The stability of the crown has great influence on the safety of tunnel itself and the buildings above, which correlates, among others, with geometrical setup of tunnel and material properties of shotcrete and soil/rock. In this paper, aiming at analyzing the stability of shotcrete supported crown, a recently presented numerical method discontinuity layout optimization is adopted, which introduces a great amount of potential discontinuities cross over one another and provides a wide search space for efficient upper limit analysis. In the analysis, a well‐established hydration model of cementitious material is implemented for accounting the hydration of shotcrete. Then assumptions based on convergence‐confinement method are used for accounting the 3‐dimensional effect in 2‐dimensional analysis, finally providing time‐space–dependent assessments of stability of shotcrete supported crown.