【正文】 or prior to the mencement of an advance in the 8th Coalbed, installing measurement tubes in the face. The values and the trend of the measured gas pressures, together with the values obtained from gas concentration tests, would enable control of the conditions of the coalbed and the establishing of what moment would be appropriate to renew the advance. The gas measurement tubes would hence be a reliable, economic control and evaluation measure of the risk of gas outbursts. Furthermore, this equipment would enable the openingof other lines of research, both for calibrating the time and range of influence of mining work in each advance, as well as for calculating the permeability of the coal. By means of the designed test (gas flow between two gasmeasurementtube sets), permeability could be estimated by numerical models calibrated with site data, both in areas of the mine that have still to be affected by mining work and in those already subject to mining works. These calibrations would also allow the variation in permeability with the depth of the coalbed itself to be analyzed.References[1] Alexeev, ., Revva, ., Alyshev, ., Zhitlyonok, ., 2004.[2] True triaxial loading apparatus and its application to coal outburst prediction. Int. J. Coal Geol. 58, 245–250.[3] Alpern, B., 1970. Tectonics and gas deposit in coalfields: a bibliographical study and examples of application. Int. J. Rock Mech. Min. Sci. 7, 67–76.[4] Beamish, ., Crosdale, ., 1998. Instantaneous outbursts in underground coal mines: an overview and association with coal type. Int. J. Coal Geol. 35, 27–55.[5] Bra252。lisis, Control y Evaluaci243。n, PhD Thesis, University of Oviedo (Spain) Publishing Service, .: 8483174340, 301 pp. (in Spanish, with English Abstract).[9] Durucan, S., Edwards, ., 1986. The effects of stress and fracturing on permeability of coal Min. Sci. Technol. 3, 205–216.[10] Flores, ., 1998. Coalbed methane: from hazard to resource. Int. J.Coal Geol. 35, 3–26 。menos Gaseodin225。 Coal R207 DTI/Pub URN 01/584, 24 pp.[8] D237。ner, 1994), which establishes a potential hazard when the fines exceed a limiting value. Although there are tabulated values for the coalbeds of the Ruhr Basin, it is not the case for the coals of the Riosa–Olloniego unit. Therefore, in this paper an improvement to the gas pressure measurement technique is proposed by developing a method and a device capable of directly measuring in situ pressures. The 8th Coalbed is a friable bituminous coal, high in vitrinite content, locally transformed into foliated fabrics which, when subjected to abutment pressure, block methane migration into working faces (Alpern, 1970). With lowvolatile content, it was formed during the later stages of coalification and, as stated by Flores (1998) this corresponds to a large amount of methane generated. Moreover, the coal is subject to sudden variations in thickness (that result in unpredictable mining conditions) and to bedparallel shearing within the coalbed, that has been considered an influence on gas outbursts (Li, 2001). Its permeability had never been quantified before in this mining area. Thus, during research in the 8th Coalbed it was decided to perform in situ tests to measure pressure transients, to obtain site values that will allow future calculations of site permeability, in order to verify if it is less than 5 mD, limit value which, after Lama and Bodziony (1998), makes a coalbed liable to outbursts. Therefore, in this study we attempted to characterize gas pressure and pressure transients, for their importance in the occurrence of gas outbursts or events in which a violent coal outburst occurs due to the sudden release of energy, acpanied by the release of significant amount of gas (Gonz225。35 s) at 2m depth, at 3 m and up to cm3 / (10 g35 s) at the only paths for methane flow are open fractures. Coal gas content is one of the main parameters that had been previously analyzed. The methane concentration in the Central Asturian Basin varies between 4 and 14 m3/t of coal (Su225。az Aguado, C. Gonz225。az Aguado, 2004) had been previously studied by the mining pany, in their internal reports. D237。 whereas the Canales series, the most important one, I 800 m thick, with 8–12 coalbeds that sum up to 12–15 m thick. This series, which contains the 8th Coalbed, the coalbed of interest in this study, has a total thickness of SanNicol225。s area and to Riosa, down to the ?800m level (IGME, 2002). The minable coalbeds of this unit are concentrated in Westphalian continental sediments (Su225。s and Montsacro”, 2004, between the University of Oviedo and the Regional Industry, Commerce and Tourism Ministry of Asturias) for achieving a better knowledge of this coalbed and its behavior in order to improve safety conditions and thus to minimize future risks. As Flores (1998) suggested, there is a relationship between gas outbursts (mine safety) and production in underground mines (efficiency of mine operations and mine economics). Since the 8th Coalbed is economical, the management has not considered the option of ending mining operations in it. The 8th Coalbed is mined via two mines: the aforementioned San Nicol225。s mine on 31 August 1995, the worst mining accide