Abstract #

This paper justifies the construction of a 15-meter ventilation tunnel connected to a main tunnel of the High-Speed Train in northern Spain. The study presents a geotechnical and geophysical analysis, focusing on the execution method for the tunnel. The document also explores a solution for excavation protection using a micropile umbrella and discusses the final conditions of use. The analysis is supported by detailed calculations and field data.

Technical Relevance #

This document is highly relevant for geotechnical and civil engineers involved in tunnel design and construction, particularly in complex geological conditions. It provides insights into the application of advanced geotechnical techniques such as micropile umbrellas and seismic refraction for tunnel stability and safety. The paper is particularly valuable for projects requiring the integration of structural design with challenging subsurface conditions.

Target Audience #

The document is intended for geotechnical engineers, civil engineers, and construction professionals who are involved in the design and construction of tunnels, especially those working on projects that involve challenging geological conditions or require sophisticated stabilization techniques. It is also relevant for researchers and students studying advanced tunneling methods.

Software and Methodology #

The methodology integrates geophysical and geotechnical approaches, specifically the use of seismic refraction techniques and FEM analysis to characterize subsurface conditions and design the tunnel structure. The paper details the geotechnical parameters derived from field tests and their application in the design of the tunnel’s support system, including the use of a micropile umbrella and HEB profiles.

Process Description #

The paper begins with a geological overview of the site, located in the Ebro basin, characterized by Tertiary deposits. The process description covers the geophysical investigation using seismic refraction to identify the soil layers and their mechanical properties. The design phase includes the selection of construction techniques, such as the use of micropiles and HEB profiles, to ensure the stability of the excavation and tunnel structure. The document also discusses the monitoring of deformations during construction, using convergence sections to track movements and ensure safety.

Main Findings #

The study demonstrates the effectiveness of the proposed design and construction techniques, particularly the use of a micropile umbrella, in stabilizing the tunnel and minimizing deformations. The seismic refraction data provided accurate input for the design, allowing for a well-calibrated structural solution. The findings emphasize the importance of integrating geotechnical and structural considerations to achieve a stable and safe tunnel under complex subsurface conditions.

Practical Applications #

The findings from this study are directly applicable to the design and construction of ventilation and access tunnels in railway and highway projects, particularly in areas with complex geological formations. Engineers can apply the insights gained from this project to similar tunneling projects, using the methodologies and techniques discussed to enhance safety and performance.

Limitations and Considerations #

The document acknowledges that while the seismic refraction method provided valuable data for the design, its accuracy depends on the quality of the field data and the interpretation of results. Additionally, the success of the micropile umbrella technique relies on precise execution and continuous monitoring during construction. Engineers should be aware of these factors and ensure thorough site investigations and careful implementation of design solutions.

Conclusions #

The paper concludes that the integration of geophysical and geotechnical analysis, combined with advanced construction techniques like the micropile umbrella, is essential for the successful design and execution of tunnels in challenging geological conditions. The case study of the ventilation tunnel for the High-Speed Train in northern Spain demonstrates the effectiveness of these methods in ensuring structural stability and safety. The study highlights the importance of a multidisciplinary approach to tunnel design and construction.

Related Resources #

Further reading includes case studies on the use of micropile umbrellas in other tunneling projects, as well as research on the application of seismic refraction techniques in geotechnical investigations. Additional resources on the design and construction of tunnels in complex geological conditions can provide deeper insights into optimizing tunneling strategies.

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