The combination of methane - air can cause potentially explosive mixtures, which in contact with an energy source can ignite, resulting not only in the destruction of infrastructure but also in the death of people. The aim of this paper is to study the ignition of methane - air mixtures with different concentration of methane, as a function of the ignition sources used and the volume and geometry of the explosion chamber. For this purpose, the 'Dynamic Behaviour of the Rock mass (DinRock)' research group of the University of Oviedo has designed and manufactured 3 explosion chambers of different sizes and shapes, instrumented with dynamic pressure sensors and accelerometers. In addition, the ignition process has been recorded with a high-speed camera. With the results obtained after a laboratory-scale experimental campaign, the maximum pressure reached, the pressure gradients and the acceleration of the pressure waves were analysed. Thus, it has been determined that the maximum pressure reached is independent of the ignition source used and the chamber volume, but not of the chamber geometry. Methane (CH4) concentrations between 8.0 and 9.0% generated the highest pressures between 1.5 and 2.5 MPa. A correlation between peak acceleration and peak pressure has also been established allowing to identify whether a deflagration or a detonation has occurred.
There is no doubt that additive manufacturing (AM) with mortars presents an opportunity within the framework of a circular economy that should not be overlooked. The concepts of reduce, reuse, and recycle are fully aligned with this technology. One of the less explored possibilities is the utilisation of mining tailings as aggregates in printing mortars. This idea not only incorporates the concept of recycling but also contributes to a reduction in the production of potentially hazardous waste that would otherwise require storage in dams, thereby decreasing long-term environmental risks and improving the management of mineral resources. We employed a mortar composed of 12.5% material derived from mining tailings to highlight aspects of AM that are typically not subject to analysis, such as the necessity of considering contact interfaces between layers in structural design, the stackability of layers during the construction process, and the behaviour under fire and seismic events, which must be taken into account during the operational phase. Without aiming for exhaustiveness, we conducted a series of tests and computational modelling to show the significance of these factors, with the intention of drawing the attention of different stakeholders—including construction companies, regulatory authorities, standardisation agencies, insurers, and end-users.
International Society for Rock Mechanics and Rock Engineering, ISRM International Symposium 2020.- EUROCK (2020. Virtual conference)
El conocimiento de los parametros resistentes y deformacionales de un terreno constituye la base fundamental para estudiar cualquier tipo de actuacion que quiera proyectarse. Sin embargo esta caracterizacion en terrenos heterogeneos como escombreras, diques de tierra, rellenos antropicos o incluso algunos suelos de origen aluvial, constituye un problema que, a dia de hoy, aun no esta completamente resuelto. Esto es debido a que los ensayos convencionales, tanto “in situ” como en el laboratorio, presentan un problema de escala que impide caracterizar el terreno en su conjunto. Por otra parte, cuando es posible la realizacion de los ensayos su coste es demasiado elevado. Por estas circunstancias el numero de muestras representativas esta muy limitado para que pueda ser extrapolable con exito a todo el conjunto.En este trabajo se describe un equipo y procedimiento de ensayo de carga “in situ” denominado Hydraulic Cylinder Test (HCT) desarrollado por el Grupo de Investigacion de Ingenieria del Terreno de la Universidad de Oviedo. Este nuevo ensayo aporta sensibles mejoras en el estudio de terrenos heterogeneos. Ademas, entre sus ventajas destacan la sencillez de su puesta en practica, la rapidez de su ejecucion y su reducido coste.A lo largo de este trabajo se describe con detalle el equipo y sus componentes, asi como el procedimiento de ensayo propuesto. A continuacion se detalla su puesta en practica mediante la caracterizacion de un dique de contencion de una balsa de lodos, situado en el sur de Espana. Con el fin de determinar la fiabilidad de los resultados obtenidos en los ensayos realizados con este nuevo procedimiento, se comparan los resultados obtenidos con los datos procedentes de una campana de investigacion geotecnica llevada a cabo previamente. Por ultimo, se extraen las conclusiones obtenidas de la aplicacion del HCT.
Purpose This paper aims to present a computational approach which – setting off from measures obtained by using an overdrilling method – determines, automatically and accurately, stress changes undergone in terrain as a consequence of human activity. Design/methodology/approach The method presented uses the data from three boreholes and the elasticity theory to represent a numerical system whose resolution allows determining the stress state in a particular point. Since the system obtained is over‐dimensioned, the Levenberg‐Marquardt minimization method has been used in order to minimize errors. This paper details the analysis carried out in order to develop the computational method. Findings This paper provides the algorithm for determining inner stresses in a particular point of a rock mass. Besides, a method to verify obtained results is presented, including its computational encoding in C#. Furthermore, the developed methods have been integrated in a computer tool which presents the results in a graphic environment. Research limitations/implications The algorithms presented are applicable when using an overdrilling method to measure stresses. Practical implications A reliable determination of global stress state demands the use of any method that is numerically difficult to use. Thus, in practice, it is of great importance to dispose of some reliable automatic tool to calculate stress state. Originality/value Accuracy in the results obtained with the tool, together with the simplicity of its interface, involves a certain advantage regarding the use of a general‐scope commercial tool, since it allows – without being necessary to be an expert user – quickly obtaining results within the analysed working area.
