Investigating the applicibaiity of lidar in the detection of ground heave and settlements in building foundations stressed by reactive black shale

摘要

A large number of buildings within the commercial district of downtown Oslo, Norway have built their foundations on black shale. The shale, when exposed to air and moisture can react in an aggressive manner. The result of the reaction can be in the form of the release of heavy metals/sulphur, the acidification of ground waters, and volumetric increases exerting large stresses on building walls and support columns. The impact will vary from shearing and cracking of walls, to settlements and sagging in ceilings, and zones of high compressions and tension around doorways. The use of lidar combined with image interpretation has enabled NGI to characterize the impact of black shale on building foundations very efficiently. The ability to quickly and accurately assess the deformations imposed from black shales has proven a valuable tool in the preliminary geotechnical investigation, for documentation of the condition of the constructions and for the design of the new foundation solutions.