摘要:

This is a case history describing a deep braced excavation in which a fully compensated raft foundation was constructed. The foundation soil is the Victoria marine clay, which is a soft normally consolidated deposit 70–100 ft (21–30 m) thick at this site. Observations were made on the deflections of the bracing and the heave of the excavation and were considered a necessary part of the design. Observations have also been kept on the settlement of the building foundation for overyears. The calculated safety factors used in bracing design and foundation design are compared against the actual performance.

ISSN:0008-3674    

DOI:10.1139/t72-028

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The need to reproduce the same stress path in the laboratory as in the field is emphasized, especially for initial consolidation, which in most cases is underKoconditions. A simplifiedKotriaxial cell is described, which permits initialKoconsolidation without any adjustments. A loading system is described, which permits a variety of stress paths during shear (either passive or active, compression or extension, by strain control or stress control loading, under drained or undrained conditions).The ease of sample preparation and test procedure is pointed out and characteristics of the new apparatus are described. Typical data are presented during both consolidation and loading under all possible stress paths, which demonstrates the consistency of results, the flexibility of the new apparatus, and the variation in soil behavior as a function of stress path.

ISSN:0008-3674    

DOI:10.1139/t72-029

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A comprehensive experimental investigation was performed on block samples of two sensitive clays taken from the sites of recent slides in Quebec. Both isotropically consolidated drained and undrained triaxial tests were carried out on specimens trimmed at various angles from the vertical direction. Direct and indirect drained tension tests were also performed so as to cover the entire stress range from tensile to compressive stresses beyond the preconsolidation pressure.Results of this study showed that the effective stress strength envelopes are pronouncedly nonlinear and strongly anisotropic in the working stress range usually encountered. The ratio of minimum strength to strength of vertical samples varies from 0.54 to 0.70. The drained tensile strength is also anisotropic, the value obtained for fracture across stratification is about three times that along stratification. The time to failure has an important effect on the peak strength.The post-peak behavior was studied and it is shown that the strength at large strains may be deduced from results of CIU and CID tests.The modulus of deformation varies with consolidation pressure in a manner similar to that of the peak strength envelope. It is essentially isotropic, but decreases with strain rate.Finally, application of these results to slope stability problems is discussed.

ISSN:0008-3674    

DOI:10.1139/t72-030

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Results of tests performed using a 1.8-m (6-ft) diameter flexible based tank capable of being filled with 3.6 m (12 ft) of water are presented. Two series of tests were performed on a muskeg with an undrained shear strength of 5–7.5 kN/m2(100–150 lb/sq.ft). The first consisted of filling the tank alone and the second with the tank positioned at the center of a 4.5-m (15-ft) diameter 0.6 m (2 ft) high flexible based reservoir. The results thus simulate the comparison of the effect of berms on the stability of embankments. Consideration is given to the short term effect of berms where they are constructed rapidly at the same time as the central fill and the long term effect where they and the central fill are constructed slowly.The resulting vertical movements were measured using a torpedo settlement gauge. The horizontal movements were measured using an inclinometer as well as a horizontal movement device. The pore pressures were measured using fine stoned piezometers.In addition suitable laboratory tests were conducted to compare predicted and measured results.

ISSN:0008-3674    

DOI:10.1139/t72-031

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Settlement records have been obtained for a two-year period during and following construction of two 43-storey buildings in mid-town Metro Toronto, Ontario. One structure is supported on caissons varying in length from 45 to 70 ft (13.7 to 21.3 m) long, belled to a maximum of 12 ft (3.7 m) diameter and supported on dense silt till. The other is supported upon a raft foundation above the till. Protected rods have been inserted in four heavily loaded caissons to determine total settlement as well as differential settlement along the concrete shaft. Settlement devices have been installed at two levels in the till below the raft foundation and a pattern of differential settlement under the building has been established. It appears that all load has reached the base of the caissons and therefore that no load of consequence is being taken by the massive caisson caps or by the shafts. The settlement under the raft follows the flexible foundation pattern only approximately. In both buildings there appears to be load redistribution due to rigidity.

ISSN:0008-3674    

DOI:10.1139/t72-032

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Engineering geology aspects of the preliminary investigation of nine alternative damsites along the lower reach of the Nelson River between Split Lake and Hudson Bay, Manitoba, Canada are described.Glacial drift, comprising mainly ablation and basal till, almost completely blankets the area, and active slope failures are common. The western part of the area is underlain by Precambrian rocks, which in the eastern part of the area are overlain by Paleozoic dolomitic limestone. Discontinuous permafrost conditions particularly presented some interesting terrain and investigation problems.The engineering geology studies included airphoto interpretation, both reconnaissance and detail geologic mapping, trenching, drilling, seismic-refraction surveys, river soundings, and ground surveys.

ISSN:0008-3674    

DOI:10.1139/t72-033

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A theory originally proposed by Gibson and Anderson (1961) has been extended to enable a direct determination of the whole undrained stress-strain curve of the clay from the pressure-expansion curve obtained in a conventional pressuremeter test.When applied to some pressuremeter tests carried out in Leda clay in the Ottawa area, the method enabled us to determine the undrained stress-strain behavior of the clay up to axial strains of about 20%. It is thought that, when properly performed, the test is able to furnish the data on the undrained stress-strain and strength properties of sensitive clays comparable to the laboratory test results obtained on block samples. Its particular feature is that it also furnishes a true picture of the post-peak strength decrease in terms of shear strain which is usually difficult to obtain by any other type of test.

ISSN:0008-3674    

DOI:10.1139/t72-034

出版商:NRC Research Press    

年代:1972

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t72-035

出版商:NRC Research Press    

年代:1972

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t72-036

出版商:NRC Research Press    

年代:1972

数据来源: NRC