Tímarit Verkfræðingafélags Íslands


Tímarit Verkfræðingafélags Íslands - 01.12.1966, Page 51

Tímarit Verkfræðingafélags Íslands - 01.12.1966, Page 51
TlMARIT VFl 1966 75 total length of almost 6000 m. Figure 10 shows the result of an analysis of the írequency of the different permeability in the layers which make up a lava field. It shows clearly that the lower contact of lava flow is by far the most permeable but the interbed has the lowest permeability. This was tested in the postglacial lava fields but there is every indication that this is a common rule independent of the over all permeability of the lava field which decreases rapidly with increasing age. In the uppermost line of figure 10 the permeability test is shown in rock which is mostly between one and two million years old. Figure 11 shows results from blow count with the Borro sound which is really nothing but a small percussion drill designed for overburden drilling only. The friction angle and indications of bearing capacity can be obtained from these diagrams. The exploration tunnel made 1962 was 258 m long and was in moraine, massive andesite and andesitic flow breccia. The diagrams on figure 12 show the progress and time studies connected with this tunnel. The damsite is situated on postglacial lava flows highly permeable and with ground water level more than 10 m below river level. The tightening effect of the silt in the river water will take care of most of the water loss but where leakage path is shortest a slurry trench is made for the safety of structures and to de- crease the loss of water. The tunnel will be in basalt lava flows usually densly jointed. It stands though very well be- cause the columns are so tight together that movement cannot occur without breaking the massive rock. The flow breccia at the contacts is much softer a rock than the basalt but it is sparsely jointed and stands well in tunnels. It is though difficult in blasting and needs much more explosives than the hard basalt. The power house is founded on tuff and tuff- rich breccia. Also a set of basaltic dikes is cross- ing the power house area. The joint pattern has strong tendency to be parallel to the dikes and faultzones and the jointfaces are often a little altered to clayish material which makes it more problematic than the joints of the basalt even if it is much closer spaced. Heimildir. Skýrslur til raforkumálastjóra flestar fjölritaðar og fjalla að einhverju leyti um jarðfræði Búrfells. Guðmundur Kjartansson 1959: Reports to the State Electricity Authority on the Geology at some sites for Potential Hydro-Power Developments in the Thjórsá and the Hvítá River systems Southern Iceland. Þorleifur Einarsson 1960: Jarðfræði Búrfellsvirkjunar. Þorleifur Einarsson and Haukur Tómasson 1962: Búrfell, General Geology. Jón Jónsson and Haukur Tómasson 1962: Búrfell, The Stratigraphy of Sámsstaðamúli. Harza Engineering Company International 1963 Búrfell Project, volume II. appendix B, Geology. Haukur Tómasson 1963: Temperature Measurements in Drillholes at Búrfell. Haukur Tómasson 1963: The Layer SMa. Haukur Tómasson and Elsa G. Vilmundardóttir 1964: Búrfell Project, The modefied Saetersmoen Scheme; Appendix: The Geology ......... Aðrar heimildir: Allan Cox, Richard R. Doell, G. Brent Dalrymple 1965: Quaternary Paleomagnetic Stratigraphy, úr The Quaternary of America. Ian Mc Dougall and F. H. Chamalaun 1967: Geomagnetic Polarity Scale of Time; Nature, v. 212. No. 5069. Trausti Einarsson 1962: Upper Tertiary and Pleistocene Rocks in Iceland, Reykjavík. Karl Terzaghai 1964: Introduction to Tunnel Geology. Rock Tunneling with Steel supports, Youngs- town, Ohio. G. Sætersmoen 1918: Vandkraften i Thjórsá Elv, Island. Jakob Björnsson og Haukur Tómasson 1862: Virkjunar- rannsóknir á vatnasviðum Þjórsár, Hvítár og Jökulsár á Fjöllum. Ársskýrsla Sambands ís- lenzkra rafveitna 1962. Haukur Tómasson 1963: Jarðfræðilegar aðstæður til virkjunar Þjórsár við Búrfell og Jökulsár á Fjöllum við Dettifoss. Ársskýrsla Sambands ís- lenzkra rafveitna 1963. Haukur Tómasson 1964: Aurburður og lekahætta úr uppistöðulónum. Tímarit V.F.l.

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Tímarit Verkfræðingafélags Íslands

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