thrust jack

This study presents the numerical modelling of tunnel segments under thrust loads of an EPB shielded TBM that utilised in Tabriz metro, Iran. Finite element analysis was used for 3D numerical investigations. Three different types of thrust jack configuration including French, German, and Japanese were applied to the segments and their results were compared. The numerical results indicate that the segment cracks are mainly concentrated in the circumferential joints in the French and Japanese configurations while the German configuration has the possibility of crushing in the longitudinal joints. By applying the maximum thrust load, the smallest tensile cracking area was observed in the Japanese configuration in comparison to the others. In the French and German configuration under the maximum thrust load, cracks were developed at the furthest point from the loading surface. Under the minimum thrust load, no crack appears in the Japanese configuration, while tensile cracks were initiated in the French and German configuration under the same load. Furthermore, the mechanical behaviour of the reinforced concrete (RC) was compared with plain concrete under various thrust loading configurations. Finally, the results of the numerical modelling are compared with the field observations for verifying of them.

This study presents the numerical modelling of tunnel segments under thrust loads of an EPB shielded TBM that utilised in Tabriz metro, Iran. Finite element analysis was used for 3D numerical investigations. Three different types of thrust jack configuration including French, German, and Japanese were applied to the segments and their results were compared. The numerical results indicate that the segment cracks are mainly concentrated in the circumferential joints in the French and Japanese configurations while the German configuration has the possibility of crushing in the longitudinal joints. By applying the maximum thrust load, the smallest tensile cracking area was observed in the Japanese configuration in comparison to the others. In the French and German configuration under the maximum thrust load, cracks were developed at the furthest point from the loading surface. Under the minimum thrust load, no crack appears in the Japanese configuration, while tensile cracks were initiated in the French and German configuration under the same load. Furthermore, the mechanical behaviour of the reinforced concrete (RC) was compared with plain concrete under various thrust loading configurations. Finally, the results of the numerical modelling are compared with the field observations for verifying of them.

Precast concrete segments used in shield tunnel linings are prone to damage in many situations. These damages can occur at different stages such as fabrication in segment factory, transportation to tunneling site, during tunneling process, and at serviceability stage. The aim of the present article is to study the damages inflicted on concrete segments during production and transportation, and to present a new classification of these damages throughout the two stages. The developed classification is based on field observations and examinations of major subway and water conveyance mechanized shield tunnels of Iran, located in Tehran, Tabriz, Mashhad, Kermanshah (Nosood) and Isfahan (Golab). The quality of tunnel lining suffers from what, as a direct consequence of any damage to concrete segments, during production and transportation, which will be also discussed in this article. For further investigation, more than 250 concrete segments from Tehran subway line 3 and 350 segments of concrete segments from Tehran subway line 7 were selected and studied for a statistical analysis of chipping and crack, consecutively. Absence of preventive measures to limit segment damages in precast segment factories is one of the main reasons for increased number of damaged concrete segments, and as a result, increased costs of tunnel construction at later stages. In this paper, production phase damages and factors contributing to these damages are studied. According to the findings of the study, the human (operator) error was the most important cause for chipping, and, time-dependent behavior of concrete was the essential reason in crack of precast segments. Eventually, final section of the article presents practical solutions for reduction of damages during fabrication and transportation of concrete segments.

This study presents the numerical modelling of tunnel segments under thrust loads of an EPB shielded TBM that utilised in Tabriz metro, Iran. Finite element analysis was used for 3D numerical investigations. Three different types of thrust jack configuration including French, German, and Japanese were applied to the segments and their results were compared. The numerical results indicate that the segment cracks are mainly concentrated in the circumferential joints in the French and Japanese configurations while the German configuration has the possibility of crushing in the longitudinal joints. By applying the maximum thrust load, the smallest tensile cracking area was observed in the Japanese configuration in comparison to the others. In the French and German configuration under the maximum thrust load, cracks were developed at the furthest point from the loading surface. Under the minimum thrust load, no crack appears in the Japanese configuration, while tensile cracks were initiated in the French and German configuration under the same load. Furthermore, the mechanical behaviour of the reinforced concrete (RC) was compared with plain concrete under various thrust loading configurations. Finally, the results of the numerical modelling are compared with the field observations for verifying of them.

Fibre-reinforced concrete (FRC) is a suitable alternative to the traditional reinforced concrete used in the manufacture of precast segments used to line tunnels excavated with a tunnel boring machine (TBM). Moreover, its use as a structural material has been approved by several national codes and by the current fib Model Code (2010). The use of FRC in segmental linings confers several technical and economic advantages, evidenced by the fact that structural fibres have been used to partially or entirely replace reinforcing bars in many TBM tunnels built over the past 20 years or currently under construction. FRC could also have been used in other tunnels, which are currently in the planning stage or under construction. However, despite its technical suitability and approval in current codes, the use of FRC was not possible in some cases. The impediment has sometimes been an incomplete understanding of the structural behaviour of the material, but a more general motive has been that comparisons of materials have taken into account only direct material costs and have not considered indirect costs or social and environmental factors. The aim of the present research is to develop a method for analysing the sustainability of different concrete and reinforcement configurations for segmental linings of TBM tunnels using the MIVES method (a multi-criteria decision making approach for assessing sustainability). This MCDM method allows minimising subjectivity in decision making while integrating economic, environmental and social factors. The model has been used to assess the sustainability of different alternatives proposed for manufacturing the segmental tunnel lining for the extension of the rail line of Ferrocarrils de la Generalitat de Catalunya (FGC) to Terminal 1 of El Prat Airport in Barcelona.

Fibre reinforced concrete is becoming widely utilized in segmental linings due to improved performance and durability of the segments. Further, significant cost savings can be achieved by replacement of traditional rebar cages with fibres. Macro synthetic fibres (MSF) are non-corrosive and thus ideal for critical environments. Recent publications have now given the basis for design and more credibility to this reinforcement type. This paper presents the design methodology for precast tunnel segments and in particular the tasks associated with the use of MSF reinforcement. A case history from the Santoña–Laredo General Interceptor Collector, currently under construction in northern Spain, is provided and will illustrate the specific benefits of MSF reinforcement for segmental linings. Proceedings of the World Tunnel Congress 2017 – Surface challenges – Underground solutions. Bergen, Norway. 2 durability (SLS) to a purely structural ULS design with more freedom in detailing and potent...

This study presents the numerical modelling of tunnel segments under thrust loads of an EPB shielded TBM that utilised in Tabriz metro, Iran. Finite element analysis was used for 3D numerical investigations. Three different types of thrust jack configuration including French, German, and Japanese were applied to the segments and their results were compared. The numerical results indicate that the segment cracks are mainly concentrated in the circumfer-ential joints in the French and Japanese configurations while the German configuration has the possibility of crushing in the longitudinal joints. By applying the maximum thrust load, the smallest tensile cracking area was observed in the Japanese configuration in comparison to the others. In the French and German configuration under the maximum thrust load, cracks were developed at the furthest point from the loading surface. Under the minimum thrust load, no crack appears in the Japanese configuration, while tensile cracks were initiated in the French and German configuration under the same load. Furthermore, the mechanical behaviour of the reinforced concrete (RC) was compared with plain concrete under various thrust loading configurations. Finally, the results of the numerical modelling are compared with the field observations for verifying of them. ARTICLE HISTORY

Precast concrete segments used in shield tunnel linings are prone to damage in many situations. These damages can occur at different stages such as fabrication in segment factory, transportation to tunneling site, during tunneling process, and at serviceability stage. The aim of the present article is to study the damages inflicted on concrete segments during production and transportation, and to present a new classification of these damages throughout the two stages. The developed classification is based on field observations and examinations of major subway and water conveyance mechanized shield tunnels of Iran, located in Tehran, Tabriz, Mashhad, Kermanshah (Nosood) and Isfahan (Golab). The quality of tunnel lining suffers from what, as a direct consequence of any damage to concrete segments, during production and transportation, which will be also discussed in this article. For further investigation, more than 250 concrete segments from Tehran subway line 3 and 350 segments of concrete segments from Tehran subway line 7 were selected and studied for a statistical analysis of chipping and crack, consecutively. Absence of preventive measures to limit segment damages in precast segment factories is one of the main reasons for increased number of damaged concrete segments, and as a result, increased costs of tunnel construction at later stages. In this paper, production phase damages and factors contributing to these damages are studied. According to the findings of the study, the human (operator) error was the most important cause for chipping, and, time-dependent behavior of concrete was the essential reason in crack of precast segments. Eventually, final section of the article presents practical solutions for reduction of damages during fabrication and transportation of concrete segments.