摘要:

As part of the development of a site in northern Quebec for a paper mill and associated townsite, a separate water intake structure and pumping works were required to serve the townsite. A timber crib intake structure was constructed approximately 200 ft. offshore in a lake, founded on very soft to soft clay, of high moisture content and sensitivity.The clay is a late glacial freshwater sediment which has been consolidated by pressures probably not exceeding the existing overburden pressure. Careful sampling and testing of the clay, however, indicated a two-part consolidation curve, with the break occurring at a point about 400 lb./sq. ft. in excess of thein situoverburden pressure. Beyond the break in the oedometer curve the compression index was up to 30 times greater than in the initial portion, being a maximum of 3.0 to 3.5.The crib was founded on a sand and gravel mattress, keyed into the lake bottom, the resulting net stress increase on the clay being slightly within the inferred range of apparent preconsolidation established by laboratory tests. Performance readings on the crib for a period of about a year after construction have substantiated the field existence of an apparent preconsolidation of about the order of magnitude predicted by laboratory tests.

ISSN:0008-3674    

DOI:10.1139/t68-001

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Before construction, standard consolidation tests indicated that the stresses imposed by a high embankment on a deep and relatively homogeneous deposit of Leda clay would exceed the preconsolidation stress and result in settlements of up to 18 in. Later, the results of more refined sampling and testing methods showed that the preconsolidation pressure had been underestimated by 1 ton/sq. ft. and that the imposed stresses would in fact fall within the recompression range. Time-settlement relationships, however, were not elastic; vertical strains continued to increase long after the embankment was completed. Field measurements of settlement are compared with values computed using compression moduli determined both from consolidation and compression tests in the laboratory.

ISSN:0008-3674    

DOI:10.1139/t68-002

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

A 26 ft. high approach fill was constructed in November 1959 for a bridge over the Rideau river near Kars, Ontario. The fill was placed over 50 ft. of Leda clay, the lower 30 ft. of which was extremely sensitive and compressible. Prior testing indicated that the preconsolidation pressure of the clay would be exceeded.Settlement gauges and piezometers under the fill have been observed since the start of construction. After 7½ years, 20 in. of settlement has occurred under the centre of the fill. Settlements are continuing at an appreciable rate although the excess pore water pressure has dissipated to a low level and is nearly constant through the clay layer.The field observations of settlement and pore water pressure are compared with values calculated and a closed form solution to the process of consolidation obtained by a heat balance integral technique and by considering the clay layer to be a rigid plastic.

ISSN:0008-3674    

DOI:10.1139/t68-003

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The Smelter of Quebec Iron and Titanium Corporation at St. Joseph de Sorel, Quebec, is located in an area which is underlain by about 80 feet of compact stratified sand, silt, and clay, followed by at least 150 feet of Leda clay. Five furnaces were constructed during 1950–52, and four more furnaces have been added subsequently. Settlement records spanning some fifteen years are available for the original furnaces.Recently, it was decided to replace No. 1 Furnace with a new unit, the weight of which will be slightly more than twice that of the existing furnace. The present furnace is founded on 32 Franki piles of 75 tons capacity; the piles are 22 feet long and are cut off about 5 feet below ground level. As it was desired to incorporate the existing piles in the foundation for the new furnace it was necessary to know whether new piles could be driven and loaded together with the existing piles without causing overstressing of the latter, which had been preloaded by the weight of the existing furnace.A settlement analysis of the existing furnace foundation was undertaken, in which sensible agreement was obtained with the observed settlements. Predictions of the rebound of the existing furnace foundation during demolition were made and these were in approximate agreement with field observations. Finally, an estimate of the settlement which the new furnace will experience was made.A significant feature of the problem is that a large portion of the total settlement experienced to date is due to consolidation of the underlying Leda clay stratum, despite the fact that the furnace foundation areas are small in size compared to the thickness of the overlying granular deposits, thereby inducing only small increases in pressure in relation to the existing overburden pressure.

ISSN:0008-3674    

DOI:10.1139/t68-004

出版商:NRC Research Press    

年代:1968

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t68-005

出版商:NRC Research Press    

年代:1968

数据来源: NRC