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

Matthew J. Lato, Erik Endre

In the proceedings of: GEO2011: 64th Canadian Geotechnical Conference, 14th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, 5th Pan-American Conference on Teaching and Learning of Geotechnical Engineering

Session: Shallow Foundations

ABSTRACT: 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.

RÉSUMÉ: A grand nombre de bâtiments commerciaux dans le centre-ville d™Oslo repose sur des schistes argileux. Lorsque les schistes argileux sont au contact de l™air, ils peuvent réagir de façon volatile. Cette réaction peut libérer des métaux lourds et du soufre, acidifier les eaux sous-terraines et générer un gonflement susceptible d™engendrer des ocontraintes importantes sur les murs des bâtiments et sur les pieux. Cela peut engendrer des fissures dans les murs, un affaissement des plafonds, et des zones de compressions ou d™extension au niveau des portes. L™utilisation du LIDAR a permis au NGI de caractériser l™impact des schistes argileux sur les bâtiments de façon très efficace. La possibilité d™évaluer avec rapidité et précision les déformations est un outil précieux pour les études géotechniques, la documentation sur les conditions des constructions et pour l™élaboration de solutions pour les nouvelles fondations.

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