Summary
The underground power station at Dinorwic includes nine caverns which are excavated largely in slate. Before construction started a number of near surface and shallow depth site investigations were carried out and were supplemented, as tunnelling commenced, with more detailed investigations underground. These investigations culminated in a trial enlargement of a full span cavern roof.
One of the principal conclusions drawn from these early operations was that it was essential to develop and carry out continuous geological and geotechnical work during the major cavern excavations including recording the discontinuities within the rock mass. This led to a comprehensive programme of geological mapping by the Engineer of all exposed surfaces whether permanent or temporary.
The short period of time between excavation and installation of support made it important that all relevant geotechnical data were collected and processed rapidly. The in-line mapping procedures set up to achieve this are outlined and the geotechnical assessment considered in the broader context of rock support design.
Résumé
La centrale souterraine de Dinorwic comprend neuf cavernes qui sont creusées en grande partie dans de l'ardoise. Avant le début de la construction, un certain nombre d'investigations de site proches de la surface ou peu profondes furent faites et complétées, lorsque l'excavation de tunnels commença, par des investigations souterraines plus poussées. Ces investigations se terminèrent par un agrandissement-test d'un toit de grotte à grand écartement.
Une des principales conclusions tirées de ces premières opérations fut qu'il était essentiel de développer et de poursuivre des travaux continus de géologie et de géotechnique au cours des importantes excavations de cavernes, y compris l'enregistrement des discontinuités à l'intérieur de la masse rocheuse. Ceci conduisit à un programme compréhensif de cartographie géologique effectué par l'ingénieur, sur toutes les surfaces exposées, qu'elles soient permanentes ou temporaires.
Du fait de la brièveté du temps entre l'excavation et l'installation d'un support, il est important que toutes les données géotechniques adéquates soient rapidement relevées et traitées par ordinateur. Les méthodes de topographie linéraire établies pour réaliser ceci sont esquissées et les évaluations géotechniques sont considérées dans le contexte plus vaste du soutènement des roches.
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McCrae, R.W., Powell, D.B. & Yu, H.T. Engineering geological mapping of large caverns at dinorwic pumped storage scheme, North Wales. Bulletin of the International Association of Engineering Geology 19, 182–190 (1979). https://doi.org/10.1007/BF02600473
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DOI: https://doi.org/10.1007/BF02600473