To leirfall frembragt ved bombeangrep.

Abstract

The clay-slides by Brøther near Lillestrøm and by Fjellvik near Sandefjord are interesting by the circumstance that they are due to bomb explosions. By Brøther near the aerodrome of Kjeller a heavy allied bomb raid took place ultimo april 1944. It caused the falling-in of a clayey hillslide. The displacement did not come all at once, but movements in the ground took place during the summer 1944. Analogueous is the case of Fjellvik. Allied bombers made an attack on ships in the harbour of Sandefjord night to april 22, 1945. 7 bombs (500 Lbs) fell on shore and caused some damage on the water supply of Framnes engine factory and some loose clay leached out. On May 5th, however, a clay-slide of about 500 sq. metres took place in the slope above two of the bomb craters. In both these cases the clay-slides are supposed to be due to pre-exisitng metastable conditions. By the bomb explosions some glacial clay have been stirred and lost part of its solidity, this being enough to cause a greater slide. No borings were carried out in the cases of Brøther and Fjellvik.