Oppsprekning, topografi og vannføring i massive dypbergarter. Meddelelser fra Vannboringsarkivet nr. 4.

Abstract

Relations between jointing, topography and ground water in massive igneous rocks. In a printed lecture on the hydro-geology of Norwegian rocks (see Nor- wegian text), the author mentions the larvikite and nordmarkite area (Permian) of the Oslo region and the granite area (Pre-Cambrian) east of the southern part of the Oslo fjord. Individual yields of drilled wells vary extremely from place to place. Further the Drammen granite (Permian) is to be classified among these rocks. Like most Norwegian ones, the rocks themselves are im- permeable, and any quantity of water to be drawn from them depends on open fractures. There are three kinds of fracturing which may be taken into consideration when a place is selected for drilling. Each kind exhibit its characteristic pattern, and they occur singly or in combination with others. The three kinds of fracturing which the author considers most important respecting ground water problems are: 1. Irregular fissures. 2. The horizont- al jointing known as sheeting. 3. Tectonical jointing. The irregular fissures are supposed to originate from temperature variations on the surface. They intersect the rocks to shallow dephts only.