Deep-seated consolidation settlements in the Fraser River delta

This paper describes the settlements of three heavy silo structures at two cement plants located along the south arm of the Fraser River delta. In this area, it has not been possible to obtain sufficiently undisturbed samples for reliable consolidation tests, and it has been necessary therefore to employ in situ tests and site improvement techniques such as preloading and vibrocompaction for the design of foundations. In some cases, piles were used to redistribute heavy loads. Observations during the past 35 years have shown that most of the consolidation settlement has occurred in a deep layer of marine sediments and that it is largely completed within 10 years of the loading. Key words: case record, consolidation, foundation performance, in situ tests, preloading, settlements, site improvement.

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Case histories illustrate the importance of secondary-type consolidation settlements in the Fraser River delta

Canadian Geotechnical Journal ◽

10.1139/t96-117 ◽

1996 ◽

Vol 33 (6) ◽

pp. 866-878 ◽

Cited By ~ 11

Author(s):

Carl B Crawford ◽

K Ian Morrison

Keyword(s):

Waste Water Treatment ◽

Treatment Plant ◽

Water Treatment Plant ◽

River Delta ◽

Waste Water Treatment Plant ◽

Fraser River ◽

True Nature ◽

Fraser River Delta

The technique of preloading the deep, compressible soils in the Fraser River delta has been used for more than 40 years to prevent excessive settlement of major structures. This paper documents 22 years of settlement under preloading and after construction of the facilities for a major waste water treatment plant in the delta. These results are similar to observations for as long as 28 years at five additional sites in the delta. It was found that as much as one half of the measured surface settlement occured during or within a few weeks of the full apllication of the preload and that subsequent settlements have the characteristics of secondary consolidation. This could not have been predicted from laboratory tests, and it raises questions concerning the true nature of consolidation in situ. For practical purposes the observations provide guidance for the prediction of long-term settlements in the region. Key words: case history, consolidation, field observations, preloading, settlement.

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Seismic site response in the greater Vancouver, British Columbia, area: spectral ratios from moderate earthquakes

Canadian Geotechnical Journal ◽

10.1139/t98-096 ◽

1999 ◽

Vol 36 (2) ◽

pp. 195-209 ◽

Cited By ~ 11

Author(s):

John F Cassidy ◽

Garry C Rogers

Keyword(s):

Site Response ◽

Strong Motion ◽

River Delta ◽

Data Sets ◽

Fraser River ◽

Spectral Ratios ◽

Data Set ◽

Seismic Site Response ◽

Fraser River Delta ◽

S Period

Three-component, digital recordings of two recent moderate earthquakes provide valuable new insight into the response to seismic shaking in the greater Vancouver area, particularly on the Fraser River delta. The 1996 M = 5.1 Duvall, Washington, earthquake (180 km southeast of Vancouver) triggered strong-motion seismographs at seven sites and the 1997 M = 4.3 Georgia Strait earthquake (37 km west of Vancouver) triggered instruments at 13 sites in the greater Vancouver area. The latter data set is especially important because it contains the first three-component recordings made on bedrock in greater Vancouver. Both data sets represent weak ground motion, with peak horizontal accelerations of 0.5-1.5% gravity (g) for the Duvall earthquake, and 0.2-2.4% g for the Georgia Strait earthquake. Using the method of spectral ratios, we estimate the site response for each of the strong-motion instrument soil sites. On the Fraser River delta amplification is observed over a relatively narrow frequency range of 1.5-4 Hz (0.25-0.67 s period), with peak amplification of 4-10 (relative to competent bedrock) for the thick soil delta centre sites, and about 7-11 for the delta edge sites. Relative to firm soil, the peak amplification ranges from 2 to 5 for the thick soil delta centre sites, and 2 to 6 for the delta edge sites. At higher frequencies, little or no amplification, and in many cases slight attenuation, is observed.Key words: seismic site response, Fraser delta, earthquakes.

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In situ estimation of the coefficient of consolidation in clays

Canadian Geotechnical Journal ◽

10.1139/t90-006 ◽

1990 ◽

Vol 27 (1) ◽

pp. 58-67 ◽

Cited By ~ 5

Author(s):

Mohammed G. Kabir ◽

Alan J. Lutenegger

Keyword(s):

Key Words ◽

Pore Pressure ◽

Reference Values ◽

Time Factors ◽

In Situ Tests ◽

Coefficient Of Consolidation ◽

Oedometer Test ◽

Undisturbed Samples ◽

Oedometer Tests

An investigation was conducted to demonstrate the applicability of cylindrical piezocone and flat piezoblade tests for providing reliable estimates of the coefficient of consolidation in clays. Coefficients of consolidation were calculated from piezocone dissipation tests for different degrees of consolidation using theoretical time factors to provide a comparison with laboratory oedometer tests. Three techniques were developed to calculate the coefficient of consolidation from piezoblade dissipation tests. Results from in situ pore pressure dissipation tests were compared with laboratory oedometer tests performed on undisturbed samples oriented in both the vertical and horizontal directions, to provide reference values of cv and ch. The results of investigations conducted at several clay sites are presented. Key words: in situ tests, piezocone, piezoblade, coefficient of consolidation, oedometer test, clays.

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