An approach to engineering geological investigations on the Island of Montreal

Abstract

In Montreal, knowledge of extent of saturated sands and marine clays is essential before the construction period begins as many foundations require the excavation of these materials. Details of clay seams in limestones and decomposed igneous sills and dykes are needed, but the discovery of areas where there is an upper zone of 10 to 20 ft (3 to 6 m) of disturbed bedrock is of greater importance. Thus investigations should be concentrated in local problems.The maintenance of an up-to-date central inventory of all geological and geotechnical data together with information on the constructional difficulties and costs involved is desirable, but it appears only practicable to index work as a general rule.The review of a past investigation showed that in an area of simple geology the standard spacing of drillholes was appropriate and successfully defined bedrock morphology and elevations; however, elsewhere on the Island only chance or a greater density of investigation may reveal bad conditions.Investigations can only be optimum if the ‘users’, the structural designers, quantity estimators, construction supervisors as well as contractors are required to acknowledge formally the impact of the geological and geotechnical appraisals upon their planning and operations including the effects of conditions suspected to be present but not actually confirmed.