Construction of Tunnels for Urban Transportation

Haack, Alfred

doi:10.2749/222137900796356035

Cited by 1 publication

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“…Due to the great responsibility that such infrastructure bears, improved monitoring and surveying strategies should be put in place to enhance the asset management of ageing structures, as well as to properly deploy efficient maintenance operations (Forero‐Ortiz et al., 2020; Garmabaki et al., 2020; Wang, 2018). For this purposes, it is essential to photograph the current characteristics and assess the actual conditions of the tunnel, especially for earlier structures for which there might not be guarantee on their consistency with the original project design (Costello et al., 2007; Gunn et al., 2018; Haack, 2004; Huston et al., 2017). Though representing the most detailed way for gathering information on the stratigraphy of a concrete structure, direct methods such as extracting core samples have certain well‐known disadvantages, including: (1) leaving weak points within the sampled element, thus requiring additional effort to properly cement the excavation hole; (2) being limited in number, thus providing a reduced spatial coverage of the segment; and (3) suffering from subjectivity in the selection of the core location.…”

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confidence: 99%

Testing of a GPR equipment to assess the integrity condition of a subway tunnel located under groundwater level

Lombardi

Lualdi

2023

Near Surface Geophysics

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Determining the condition of underground concrete tunnels is fundamental for ensuring continuity and safety of operations, as well as for deploying efficient maintenance plans. The increased traffic volumes in early infrastructures, which are characterized by outdated construction techniques and potential approximated realization, as well as rising groundwater levels due to variations in urban industrialization patterns, are among the main causes of current concerns regarding their performance. Such uncertainties and constraints push towards the use of non‐destructive techniques, rather than direct methods, to gather the required knowledge on the actual status of structures. This study presents the results of a ground penetrating radar (GPR) investigation carried out in a subway tunnel segment to characterize the thickness of its underlying concrete elements, namely the tunnel invert and the concrete filling, deemed necessary after relevant flooding events prompted the evaluation of its overall integrity condition. A preliminary step was performed to define the optimal frequency and polarimetric antenna configuration, given the resolution and penetration requirements and considering the high electromagnetic interference characterizing the site. The selected configuration was then assembled in a dedicated survey platform, and an entire 650 m long segment surveyed, producing a high resolution delineation of the concrete elements thickness. The accuracy of the estimation has been validated through nine core samples, demonstrating the reliability and consistency of the conceptualized GPR platform.

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