High-speed railway tunnel monitoring using point, long gauge and distributed strain and temperature fiber optic sensors

La monitorización de estructuras es una rama de la ingeniería estructural que está captando mucha atención actualmente. Las deformaciones y temperaturas son, habitualmente, los parámetros monitorizados porque son los que mejor representan el comportamiento estructural. De todos los tipos de sensores existentes, los basados en fibra óptica resultan especialmente interesantes debido a sus ventajas comparativas sobre los sensores convencionales. En este artículo se presentan los trabajos de monitorización de la estructura de un túnel artificial de Alta Velocidad construido en Mogente (España) mediante tres tipos de sensores ópticos desarrollados por los autores. Los resultados de los sensores se comparan con los proporcionados por un modelo teórico de elementos finitos. Esta comparación confirma que los sensores reproducen notablemente bien la pauta general de comportamiento de la estructura, incluso con pequeños niveles de deformación (5µε). Por último, el artículo discute el comportamiento de los sensores, sus mediciones y sus campos de aplicación.Structural Health Monitoring (SHM) is presently having a great development. Strains and temperatures are usually the key parameters to be monitored due to their relevance when explaining structural behavior. Several types of sensors are used in SHM, but fiber optic sensors are especially interesting due to their advantages with respect to conventional sensors. In this paper, the monitoring of a high-speed train tunnel recently built in Spain using three types of fiber optic sensors developed by the authors is shown. Results given by the sensors are compared to those provided by a theoretical model built using FEM. Comparison of measurements and theoretical results confirms that the sensors reproduced remarkably well the general patterns of the tunnel structural behavior, even when strains are relatively small (around 5 µε). Finally, the paper discusses the behavior of the sensors, their measurements and their field of application which is useful for researchers and practitioners.Los autores quieren agradecer a la Universitat Politècnica de València, al Ministerio de Educación por la financiación recibida a través del proyecto BIA2011-27104 y al Ministerio de Fomento por el apoyo recibido a través del Proyecto SOPROMAC (P41/08)

Marine Aerosol Weathering of Mediterranean Calcarenite Stone: Durability of Ethyl Silicate, Nano Ca(OH)2, Nano SiO2, and Nanostructured Consolidating Products

Calcarenite stone samples from a historic building (Bizerte, Tunisia) were collected and treated under different environmental conditions with several consolidating products: alkoxysilane (ethyl silicate), a surfactant-templated novel sol–gel, Ca(OH)2, and SiO2 nanoparticles. These were subjected to marine aerosol accelerated aging cycles and studied by several non-destructive tests and techniques to assess the stability of the products. Results show that weathering caused by salt crystallization is not inhibited but it is slowed down due to the enhancement of superficial mechanical properties (surface cohesion and micro-hardness) achieved after one month of treatments application. A high or low relative humidity of the consolidation environment significantly affects the final mechanical and aesthetical physical properties and therefore conditions the durability of the treated substrates, even producing higher damage than observed in the blank specimens, depending on the product

Salt weathering in desalinated and non-desalinated ceramic amphorae from underwater marine environments

This article reports on a study of Iberian, Italic and Tarraconensian amphora sherds found in different underwater marine environments. Non-desalinated fragments were compared to fragments desalinated using the procedure normally applied to underwater archaeological objects to study the efficacy of the method and determine both the state of conservation of the materials and the decay caused by salt weathering. To that end, destructive (X-ray diffraction, ion chromatography, scanning electron microscopy coupled to energy dispersive X-ray spectroscopy, mercury intrusion porosimetry) and non-destructive (computerized X-ray tomography) tests were conducted on the samples. The conclusion drawn was that the long-term salt content is closely related to firing temperature and that non-desalinated samples or samples in which desalination was not wholly effective exhibit a variety of signs of degradation that can be detected with computed tomography. CT proved to be a powerful technique for visualising and locating salts in the interior of porous materials. Keywords: Underwater ceramics, amphorae, desalination, salt weathering, durabilit