Foundation problems in Champlain clays during droughts. II. Case histories

Abstract

This paper presents the results of a 3 year monitoring program of the volumetric water content in two clay deposits on Montréal Island. The water content was monitored by means of a neutron depth moisture probe, which was lowered down in a series of 3–6 m deep, permanently installed, aluminium access tubes. These tubes are located at various distances from deep-rooted trees on two experimental sites. On the first site, a two-storey reinforced concrete building, surrounded by four rows of 15–20 m high silver maples, has suffered a differential settlement of over 150 mm. On the second site, a three-storey apartment block, surrounded on two sides by a row of 5–10 m high maples, has suffered a differential settlement of about 50 mm. The paper analyses the volumetric water content variations and compares them with both the rainfall deficits calculated for the period of observation and the elevation profiles of the building foundations. In addition, a comparison is made between the observed damages and a classification proposed by the Building Research Establishment of England. Key words : volumetric water content, trees, settlement, distortions, clay deposits, seasonal variations, damages.