Austrian Tunneling Method Research Articles

Improved Subsidence Assessment for More Reliable Excavation Activity in Tehran

This paper presents a particular tunneling method, the new Austrian tunneling method (NATM), which plays an important role in reducing subsidence of the surface and damage to structures in urban areas. It has a wide range of applications in shallow tunneling projects all over the world. In this study, numerical modeling of the third-line Metro tunnel in Tehran, which is designed and stabilized by the NATM, is under discussion. The foregoing tunnel is excavated manually with a one-meter advancing step. In this project, the constructors use a lattice girder and spray concrete with 31 cm thickness as the initial lining. A suitable numerical software for this modeling is PLAXIS 3D Tunnel, which allows high-resolution finite element modeling (FEM) of the studied object. The performance of this method is investigated and compared with that of other NATMs. The numerical modeling yielded a value of 30.01 mm for earth subsidence in the most damaged area of the settlement, which was confirmed with a dramatically low difference by earth surface monitoring. Moreover, this tunnel was drilled and excavated using various methods, among which the least settlement was obtained by the proposed method. The results are promising, and they indicate that tunneling with this method should continue to be used to expand the subway line in the city.

An overview of potential excavation compensation method for tunnelling in deep rock engineering

The complicated geological environment of deep rocks poses new challenges to tunnel and mining engineering. Some thorny disasters such as large deformation of soft rock and rockburst are becoming more and more prominent. However, the classic tunnelling methods represented by the mine tunnelling method and the new Austrian tunnelling method are generally unsatisfactory in addressing these issues due to the limited self-stability of surrounding rock mass. Therefore, the excavation compensation method (ECM) with the core of active stress compensation has been proposed and applied in practical engineering construction to solve the above problems. After extensive engineering practice, the theoretical foundation, key technologies, and construction system of ECM have been established and improved. This article provides a comprehensive overview of this novel tunnelling method. In addition, its controlling effects on surrounding rock are demonstrated by two typical engineering examples. It could provide some new ideas and references for the development of future tunnelling technology.

Shallow tunneling's impact on surface settlements

The research described in this paper deals with the impact of shallow tunneling on surface settlements in urban areas. The study focuses on carrying out a numerical analysis and a parametric geotechnical study to investigate the effects of tunnel excavation on the surface ground, particularly with regard to distortion and potential damage to structures above the tunnel. To carry out the study, the researcher used a finite element method (FEM) software package called Plaxis. This software is commonly used for geotechnical analysis and allows simulating and analyzing the subsurface conditions in Algiers underground in the context of excavating a shallow tunnel. The New Austrian Tunnelling Method (NATM) excavation method was chosen for the study. The results of the numerical analysis are presented in terms of displacements. The results indicate that ground flow has a significant influence on ground movement, probably contributing to surface settlement. However, the effect of tunnel excavation on the lowering of the water table and Young's modulus (a measure of soil stiffness) is relatively small in comparison. The research provides valuable information on the potential impacts of shallow tunneling in urban areas and the factors that play a crucial role in determining the extent of ground movement and surface settlement. By using numerical analysis and conducting a parametric geotechnical study, and gives valuable insights into the potential impacts of shallow tunnelling in urban areas and the factors that play a crucial role in determining the extent of ground movements and surface settlements. By using numerical analysis and conducting a geotechnical parametric study, and contributes to a better understanding of the behavior of the ground during tunnelling operations in Algiers. The findings can be helpful in designing future tunnelling projects to mitigate potential risks to structures and infrastructure located above the tunnels.

INNOVATIVE TECHNOLOGY FOR THE CONSTRUCTION OF A PYLON STATION OF THE METRO BASED ON THE EXPERIENCE OF USING NATM

Purpose. For quite a long time, the metro station of the pylon type of deep contour interval was considered an underground structure that no longer has development potential. However, after the introduction of innovative technologies during the construction of the Dnipro metro, in particular the New Austrian Tunneling Method (NATM), this design is being used again and has developed further use. The purpose of the scientific article is to analyze innovations in the technology of construction of a three-vaulted pylon metro station from precast reinforced concrete using NATM, which require scientific justification. Methodology. In order to achieve the goal, the traditional technology of constructing a deep contour interval pylon station was revised. An analysis of the features of NATM, which allow it to be used during the construction of a pylon station in strong rock, has been carried out. A step-by-step analysis of the construction of the station was implemented with the involvement of mathematical modeling based on the finite element method. For this purpose, a number of finite-element models of each stage of construction of a pylon-type station have been created. After the numerical analysis, the indicated models were adjusted in accordance with the changes associated with the new construction technology. Findings. The value of the stress-strain state of the pylon station was obtained during the numerical analysis of each stage of construction. Stress analysis proves the possibility of applying innovative construction technology in the case of a pylon station. Originality. On the basis of the performed numerical analysis of the phased construction of a pylon station based on NATM, dependencies were obtained that allow revising the existing concept of the construction of this type of station in strong rocks. The obtained data justify the application of NATM and release the potential of the analyzed underground structure. Practical value. The substantiation of the innovative technology based on NATM allows expanding the scope of its application and successfully carrying out the construction of such complex underground facilities.

Key principles of stress control method

Underground excavation would cause two main excavation effects: (1) stress redistribution, including radial stress decrease and tangential stress concentration; and (2) surrounding rock degradation. Comprehensive consideration of excavation effects is crucial to prevent underground engineering disasters. However, the two excavation effects are not considered in the predominantly used Platts pressure arch theory, whereas the New Austrian tunneling method is focused on the full utilization of the strength of the surrounding rock. Construction designing using these methods could lead to disaster deep underground. Thus, in this study, the stress control method (SCM) was proposed to comprehensively consider the two excavation effects. The following two key SCM principles were introduced in this study: (1) adopt the largest possible prestressing force to increase the low radial stress caused by excavation; (2) timing of support should be as early as possible to minimize surrounding rock deterioration. The application principles of SCM in hard rock tunnels and soft rock tunnels are explained

Settlement control in large span tunnels under shallow over burden: a case study of the Arash-Esfandiar-Niayesh tunnel

Settlement control is pivotal in the construction of large span tunnels, particularly when situated under shallow overburden. The importance of settlement control in the context of the Arash-Esfandiar-Niayesh tunnel project, a multi section tunnel designed to facilitate two-way traffic in Municipality of Tehran District 3, is studied. The tunnel, which possesses an overburden of 4–15 m, faces unique challenges such as low overburden, urban location, and proximity to tall structures. By integrating the New Austrian Tunneling Method (NATM), this paper examines the effects of various support systems on construction of the tunnel project. Two critical sections are analyzed, and the settlement control strategies are examined according to a combination of various support elements. Analysis and numerical modeling based on PLAXIS 2D finite element code revealed the impact of these support systems on ground settlements on the structural and geotechnical stability. They had a substantial impact of tunnel geometric shape on sustainability and stress distribution. The inadequacy of common support systems, especially in tunnels with a horseshoe section, is highlighted. The impact of removing temporary lattice girderson surface settlements emphasizes the importance of settlement monitoring. Field data, including a maximum vertical displacement of 2.6 cm on the ground and in the tunnel, validate the numerical analysis results. Despite the challenges, the consistency between numerical and instrument data underscores the effectiveness of settlement control strategies.

Assessment for shallow and large tunnel construction in weak ground conditions: Application of tunnel boring machines

AbstractWith recent technological advancements, tunnel boring machines (TBM) have developed and exhibited high performance in large diameters and weak ground conditions. Tunnels are crucial structures that significantly influence the timelines of highway and railway projects. Therefore, the construction of tunnels with TBMs becomes a preferred option. In this study, a comparative analysis between TBM and the New Austrian Tunneling Method (NATM) for tunnel construction is performed in the construction of the T1 tunnel with a diameter of 13 m, which is the longest tunnel in the Eşme‐Salihli section of Ankara‐İzmir High‐Speed Railway Project (Türkiye). The selection of TBM type, measures taken in problematic sections, and application issues of TBM are discussed. The impact of correct description of geological and geotechnical conditions on both selection and performance of TBM is presented. An earth pressure balanced type TBM is chosen for the construction of the T1 tunnel. Because of the additional engineering measures taken before excavation in problematic areas, the tunnel was completed with great success within the initially planned timeframe. From this point of view, this study is an important case and may contribute to worldwide tunneling literature.

Automatic tunnel point cloud creation using photogrammetry and deviation analysis of excavation and shotcrete surfaces

AbstractDuring new Austrian tunnelling method excavation, it is necessary to carry out an analysis of the compliance of the actual surfaces with the theoretical lines prescribed in the support types for each tunnel excavation step. With our own software solutions, we created point clouds of the excavation and shotcrete of the primary tunnel support through the automated process of photogrammetric data. Together with the tunnel axis and theoretical profiles, the georeferenced and filtered point clouds were then used in the analysis of the deviation from the theoretical lines of excavation and primary support shotcrete and shotcrete thickness. The final products of the independent analysis are deviation profiles and unwrapped extrados views with numerical results and a color legend.

Viscoelasticity of hydrating shotcrete as key to realistic tunnel shell stress assessment with the New Austrian Tunneling Method

The New Austrian Tunneling Method (NATM) essentially rests on observational information concerning displacements measured in selected positions at the inner surface of shotcrete tunnel shells. The combination of these measurements with advanced material and structural mechanics, in the course of so-called hybrid methods, have successfully delivered, for more than 20 years, practically relevant estimations of internal and external forces and corresponding degrees of utilization. The reliability of the latter, however, may crucially depend on the used material model. Based on a recently proposed analytical structural mechanics model [Acta Mech 233, 2989–3019 (2022)], and focusing on the benchmark example of measurement cross section MC1452 of the Sieberg tunnel, driven in the 1990s in Miocene clay marl, the present paper compares the estimations of forces and degrees of utilization arising from differently refined constitutive concepts, namely (i) aging elasticity, (ii) aging linear viscoelasticity, and (iii) aging nonlinear viscoelasticity. It turns out that only the consideration of aging nonlinear viscoelastic material behavior provides access to realistic values for the degree of utilization, being lower than one. Simpler material models would indicate local material failure, which was not observed in situ.

Performance of the Flexible and Rigid Lining under Earthquake Impact and Weakness of the New Austrian Tunneling Method (NATM) Principles, a Specific Case Study of the Bolu Tunnel

The Bolu tunnel is located between the Istanbul-Ankara Highway and its construction took approximately 13 years. Since the beginning of the tunnel excavation, serious deformations and stability problems have been encountered. The basis of the problems encountered during the tunnel excavation is the fact that the geological units through which the tunnel passes are very weak and fault lines cut the tunnel location. The fault lines pass through secondary faults in the seismically active North Anatolian Fault. At these fault crossings, deformations occurred continuously so that revisions had to be made in the support systems. The 12 November 1999 Düzce earthquake occurred on the Düzce fault and a surface rupture 40 km long was caused. The rupture terminated 1.5 km west of the tunnel; it did not reach the tunnel. Throughout the earthquake, instances of collapse occurred at the areas excavated on the fault line at the entrance of Elmalık and where the deformations exceeded 1.0 m; this section of the tunnel had to be abandoned. After these problems, a new improved design for tunnel excavation was developed. These new support systems, which are Bernold lining and bench pilot tunnel systems, contain allowance for rigid lining that is the opposite of the new Austrian tunneling method (NATM) principles. Within the scope of this study, the causes of the collapse in the tunnel are investigated and the effect of the Düzce earthquake on the tunnel is discussed. Also, the applicability of the NATM in tunnels excavated on weak zones is also discussed.

Surface and Subsurface Engineering Geological Characterization for Empirical Design Excavation Method and Support System of Jragung Dam Diversion Tunnel, Indonesia

The diversion tunnel of Jragung Dam was initially designed using the New Austrian Tunnelling Method (NATM) based on assessment of limited drill cores. Due to the uncertainty in the use of single empirical tunneling method and limited data for the tunnel design, this research was conducted to better characterize the rock masses and provide design alternatives for the tunnel construction. In addition to drill core evaluation, surface engineering geological mapping was carried out to obtain complete parameters of Rock Mass Rating (RMR) and Q rock mass classifications for designs of the tunnel excavation method and support system. The results show that the tunnel area consists of highly weathered sandstone and claystone layers with extremely poor to fair rock mass quality. The rock masses have very favorable and fair discontinuity strike and dip orientations with respect to the tunneling direction. The recommended excavation methods are top heading and bench and multiple drifts. The tunnel mostly requires rock bolt and shotcrete support system and the tunnel sections with poor rock mass quality require additional installation of steel sets. This research highlights potential collapse of the extremely poor quality rock masses near the tunnel portals during excavation of the diversion tunnel.

Substantiation of the Escalator Tunnel Construction Technology Based on the Results of Field Research

Purpose. The authors aim to substantiate a new technology for the construction of an escalator tunnel in Ukraine based on the results of field studies performed as part of surveying measurements during the construction of the inclined run of the Dnipro metro. Methodology. The article analyzes the main technology of the escalator tunnel construction, which was based on the development of an inclined working from top to bottom with preliminary preparation of the massif by means of artificial soil freezing. Several cases of application of the bottom-up escalator tunnel construction method using the New Austrian Tunneling Method (NATM), which is successfully used in metro of other countries, are considered. The main principle of the method is that a shotcrete system is used as a temporary (primary) support, and a reinforcement system with monolithic concrete is used as a permanent support. Findings. The authors analyzed the peculiarities of the escalator tunnel excavation of the Dnipro metro by the Turkish company «Limak» in 2017–2018. It was noted that the excavation was carried out from the bottom up in conditions of strong rock (plagiogranite) using drilling and blasting operations. The characteristic results of field studies during drilling and blasting operations in the process of developing the calotte are analyzed. On the basis of these data, it is possible to trace the tendency to the appearance of minor overburden during sinking. The value of the deformed state (displacement of the contour of the designed casing) is within the normative limits, which indicates the effective use of these works within the framework of NATM. It is proved that in the conditions of military operations, the technology of building an escalator tunnel from the bottom up is a guarantee of the safety of workers and equipment. Originality. The results of the scientific work presented in the article make it possible to determine the level of deformed state during the excavation of the escalator tunnel of the Dnipro metro in hard rocks. During the field studies, the dependences of deformation of plagiogranite in the inclined bore were obtained. Practical value. An alternative technology for the construction of a bottom-up escalator tunnel based on NATM with the provision of normative deformation of the surrounding rock mass is substantiated.

Regularities of the stress state of the rock massif around the single-vault station under construction by NATM

Subway stations are underground facilities of high responsibility. The use of new construction technologies requires their scientific justification. The single-vault station “Teatralna” of the Dnipro Metro is designed as one that is under construction by the New Austrian tunneling method. Since this type of station is a working of a large cross-section, it is necessary to determine the stress state of the rock massif, which affects the temporary fastening. The finite-element model is developed, which shows the stages of cross-section opening. The developed model reproduces the layout of the subway station in the rock massif and the characteristics of the temporary fastening. The numerical analysis for six stages of station construction is carried out. The distributive features of horizontal stresses and the asymmetry of the stress state of the rock massif are clarified. For the first time, the regularities of the rock massif around the single-vault station under construction by the New Austrian tunneling method are obtained. It is established that the maximum of horizontal stresses appears at the stage of opening the lower left part of the cross-section.

A Study of Vibration Reduction Effects of TBM and NATM Parallel Construction Methods according to Tunnel Depth and Size

The new Austrian tunnelling method (NATM) and tunnel boring machine (TBM) are methods for excavating underground spaces. The NATM construction method has noise and vibration problems, and excavation using TBM has the disadvantage of high initial cost and is limited by ground conditions. A parallel TBM and NATM construction method has been developed to overcome these limitations. However, research on the TBM and NATM parallel construction method is lacking, and it is crucial to identify the applicability of the TBM and NATM parallel construction method in advance by applying it to various ground and blasting conditions. In this study, based on the vibration measurement data of the excavation site using the NATM construction method, the vibration measurement values generated when excavating the top surface using the existing NATM construction method and the TBM and NATM parallel construction methods were compared. Lastly, the vibration reduction effect of the two construction methods was analysed according to the tunnel excavation depth and tunnel size through 3D numerical analysis. As the depth of tunnel excavation increases, the vibration at the ground surface is reduced by up to 83%. In addition, as the ratio of the size of the blasting surface with NATM and the excavation surface with TBM is closer to 1.0, the vibration decreases.

Investigation of the Effect of Tunnel Geometry on Deformations in Shallow and Stratified Rock Formation

Tünel içindeki deformasyonlar, üst yapıdan gelen sürşarj yükü, aşırı yükleme, kayaç veya zemin biriminde oluşan içsel gerilmeler ile diğer faktörlerin bir sonucu olarak ortaya çıkar. Tünel içi deformasyon ölçümü, tüneldeki plastik şekil değiştirmenin büyüklüğünü belirleyebilmek için önemlidir ve tünel güvenliğinin izlenmesinde önemli bir safhayı oluşturur. Bu çalışmada, dört tabakalı bir kaya formasyonunda ve yeraltı suyu etkisinde bulunan, at nalı veya yumurta şeklinde tasarlanan, NATM (Yeni Avusturya Tünel Açma Metodu) tekniği ile kademeli olarak açılacak olan tünellerin üç boyutlu ve doğrusal olmayan davranışları sonlu elemanlar yöntemi ile analiz edilmiştir. Kazı adımlarına göre farklı yükleme koşullarına maruz kalan taç ve tünel çevresinde meydana gelen kalıcı deformasyonlar ayrıntılı olarak incelenmiştir. Ayrıca her iki tünel geometrisinde, bütün kazı aşamalarında tünelin kritik kesitleri boyunca oluşacak olan kalıcı şekil değiştirmeler, deformasyon eğrileri sayesinde göreli olarak karşılaştırılmıştır. Sığ ve tabakalı kaya ortamında tasman ve konverjans miktarının azaltılmasında, tünel geometrisinin at nalı tipi yerine yumurta şeklinde seçilmesinin daha avantajlı olduğu tespit edilmiştir.

Study on structural mechanical characteristics and safety warning of NATM tunnel in aquifer

With sustainable developments in transportation facilities, the construction of the undersea tunnel has become inevitable. Controlling the construction and operation of the undersea tunnel structures dynamically and ensuring their safety is of primary concern. Therefore, using the rich water mountain section of the Lujiazhi subsea tunnel constructed by NATM (New Austrian Tunnelling Method) as a case study, an intelligent real-time tunnel health monitoring system integrating tunnel monitoring, wireless transmission and safety assessment was developed. The monitoring results show that the surrounding rock water pressure, earth pressure and stress of the secondary lining structure experienced stages of rapid change, continuous change and stability. The tunnel substructure is relatively weak as a whole, and the left invert is the weakest part of the whole structure. It was suggested to optimize and reinforce the tunnel substructure accordingly. The rationality of the tunnel drainage system and reliability of field test data are verified by numerical simulation. Finally, the real-time fuzzy comprehensive evaluation model of tunnel operation safety conditions based on online monitoring data is established to realise the real-time evaluation and early warning of Lujiazhi tunnel structures’ health conditions. HIGHLIGHTS An intelligent real-time tunnel health monitoring system is developed. The deformation characteristics of submarine tunnel are revealed. The submarine tunnel drainage system rationality of lining structure are proved. The safety evaluation model of submarine tunnel structure is proposed.

The Relation of the Method Used in Tunneling Operations with the Geological Structure Example of the Black Sea Coastal Road

Transportation tunnels are the most preferred method to facilitate transportation in mountainous and rough terrains. The excavation method and the choice of fortification tools in tunnel construction depend on the geological structure of the tunnel route. Correct formation determination and determination will reduce the cost and eliminate many risks. The Black Sea region has a very mountainous and rugged terrain. The most obvious method used to overcome rough terrain is road tunnels. The rock classification of the tunnel route and the support to be formed accordingly are very important in the selection of the method to be applied in the highway tunnel constructions. Within the scope of this study, Trabzon-Akyazi region, which is an important part of the Black Sea coastal road, was studied. The geological formations on the route of the 3-lane and double-tube tunnel with a length of approximately 2476 meters, which is planned to be built within the highway passing through this region, were examined and the method used in the tunnel construction was determined. As a result of the analyzes and calculations, it has been determined that the dominant unit along the tunnel routes is the agglomerate of the Besirli formation and the New Austrian Tunneling (NATM) method is applicable. The rock classes found were determined to be B3 and C2 classes according to NATM. Excavations in the tunnel were carried out by drilling and blasting method in the form of the upper half and the lower half.

A Geotechnical Perspective on a Complex Geological Environment in a High-Speed Railway Tunnel Excavation (A Case Study from Türkiye)

The T26 tunnel was designed within the scope of the Ankara-Istanbul high-speed railway in accordance with the speed of 250 km/h. Some serious problems and excessive deformations were encountered during the excavation works. The deformations in the tunnel caused subsidence on the surface and the Tunnel Boring Machine (TBM) became stuck; therefore, tunnel excavation works were suspended. Design works for re-excavation in the T26 tunnel and extracting of the TBM were carried out and the tunnel was re-designed by the New Austrian Tunneling Method (NATM) system. The main purposes of the present study are to describe the problems encountered during the T26 tunnel and to discuss the sources of the problems. The advantages and disadvantages of TBM and NATM methods for the tunnel having difficult ground conditions were discussed. Critical points needing to be considered for the tunnels excavated with TBM through weak ground conditions and the effect of the TBM selection process were discussed. Considering the complex geological and geotechnical structure of the tunnel route, it is possible to say that the T26 case is an interesting case for tunnel engineering. Along the tunnel route, landslides, high seismic activity, groundwater conditions, and extremely weak rock mass features coexist. Therefore, the tunnel route is a very complex environment. However, due to the geometric limitations of the high-speed railways, relocation of the route is not possible. The experiences gained from tunnel excavations under difficult conditions are capable of bringing new horizons to future tunneling studies.

Application of the NATM Methodology for the Excavation of Rail Tunnel in Difficult Geological Conditions: A Case from Garhwal Himalaya, Uttarakhand

Abstract The documentation of excavation method and support design based on rock mass classification systems i.e. rock mass rating (RMR), Q-system and New Austrian tunneling method (NATM) for adit-7 tunnel being constructed in Garhwal Himalaya, India is discussed in this paper. The New Austrian tunneling method classes of rock units have been developed by using correlations with the RMR and Q systems, according to the ONORM B 2203. NATM principles were used because the geological conditions were continually changing. The study indicated that the RMR-based rock mass estimation was overstated, but the qualitative assessment was right. The NATM technique is more adaptable for Garhwal Himalayan rocks having various uncertainties in rock mass evaluation. The current adit investigations indicate that there are numerous unanswered concerns, concerning rock mass quality evaluation, tunnel behavior during construction and usability. Results of the analysis are considered to be useful for the design of the new tunnels constructed in the similar type of the terrain.

Research on Tunnel Construction Monitoring Method Based on 3D Laser Scanning Technology

A tunnel is a symmetric structure working under uncertain load. In the traditional method of monitoring and measurement of tunnel deformation, only a small number of symmetric measuring point displacements are engaged to represent the overall deformation of the tunnel, and it is difficult to fully reflect the displacement changes of the tunnel during the construction process. In this paper, a deformation monitoring method is proposed for the tunnel construction process based on 3D laser scanning technology. Initially, 3D laser scanning was used to obtain scattered clouds of irregular structures considering the New Austrian Tunneling Method (NATM). Afterward, the modified B-spline interpolation and greedy triangulation were used to fit the surfaces. Moreover, the normal vector matrix was innovatively applied to express the deformation of the tunnel fitting surface, which solved the problem of scattered point clouds in 3D laser scanning. A normal vector was obtained by the intersection of the normal of one fitted surface with the other. Subsequently, the maximum entropy method was introduced to form the probability density function of the normal vector, and the 1% and 5% probability eigenvalues were used to analyze the overall deformation trend of the tunnel. Finally, the eigenvalue of 5% probability, which was less affected by construction uncertainties, was selected for analysis. This way, the analysis and prediction method for overall tunnel deformation was established.