摘要:

Shrinkage is one of the important soil phenomena in which an engineer is interested. The various factors affecting shrinkage phenomena are discussed. The investigation deals with theoretical and experimental studies of the physical mechanism involved in the process of shrinkage of a clay soil. A modified effective stress concept has been made use of for a satisfactory explanation of the phenomena. The relative importance of dielectric constant (in effecting the electrical attractive and repulsive forces) and the surface tension on the shrinkage of a clay has been brought out, using various organic solvents as pore fluids. Kaolinite has been used in the experimental investigation which includes conventional shrinkage limit tests, tests on samples consolidated to 1 ton/ft2(1.093 kg/cm2) with different fabric as well as the same initial fabric, tests on samples consolidated to different pressures, and finally tests on samples with constant external applied pressure. The experimental results reveal that the modified effective stress concept proposed governs the shrinkage phenomena. Though surface tension is believed to be the cause of shrinkage, it has been shown that the void ratio at the shrinkage limit is governed by the contact stress at particle contact and (or) between particles, as defined by the modified effective stress concept. The role of fabric and externally applied load on shrinkage is discussed.

ISSN:0008-3674    

DOI:10.1139/t71-052

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The paper gives results of field studies on uplift forces on small-diameter columns of steel, concrete, and wood caused by adfreezing in frost-susceptible Leda clay. Adfreeze strength values would appear to be highest for steel and concrete, followed closely by wood. The heaving pattern and the heaving force transmitted are shown to be different for long foundation walls than for isolated columns. This compares favorably with the deformation pattern induced in an ice cover around offshore structures, during a change in water level. Attention is also given to the relative movement of the heaving soil with respect to the structure and the influence of the heave pattern on the transmission of forces.

ISSN:0008-3674    

DOI:10.1139/t71-053

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Detailed observation on settlements during construction of the CN Tower in Edmonton has afforded the opportunity of calculating the influence of the settlements on the distribution of foundation loads for an actual three-dimensional frame structure. These calculations have been carried out using the computer program ICES-STRUDL II. It is shown that in performing a soil–structure interaction analysis, the variation in structural rigidity with story height cannot be ignored when settlements occur during the construction period. Moreover, the distortions of a real structural frame due to small differential settlements can generate reactions of appreciable magnitude. As much as 39.4% of the basic load action on a footing beneath the CN Tower has been generated by a local maximum differential settlement which never exceeded 1.4 cm.

ISSN:0008-3674    

DOI:10.1139/t71-054

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The undrained shearing strength of Welland clay is determined over a range of sample orientation of 180° by the use of semiconfined compression tests that limit failure to one direction, but allow failure on any plane in that direction. It is shown that the undrained shearing strength is very nearly symmetrical abouti = 90° and that the Bjerrum-Kenney hypothesis of greatest resistance to shearing stress in the direction of greatest shearing stress during consolidation is nearly so for Welland clay, but the two are slightly out of phase. For the soil tested, semiconfined tests yield undrained shearing strengths about 20% greater than unconfined compression tests.

ISSN:0008-3674    

DOI:10.1139/t71-055

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The comparison of consolidated undrained triaxial results on sensitive Leda clay sampled by six different sampling methods is presented. The results indicate that the failure index, represented by the axial stress difference as a fraction of the axial failure stress difference against strain plots, are widely different at very low consolidation pressures, but are similar and approximate to the results from block samples as the consolidation pressure is increased. The pore pressure coefficientAappears to be independent of the sampling method and remains remarkably consistent throughout any test (up to failure) except where the confining pressure is very low or above the preconsolidation pressure.Routine commercial sampling methods (including laboratory preparation) using 50-mm diameter samples were found to partially destroy the cementation bonds, causing a decrease in strength at low confining pressures and an unsafe increase in strength at medium confining pressures. This trend is decreased by better sampling.

ISSN:0008-3674    

DOI:10.1139/t71-056

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

The physics of consolidation of a thawing soil is formulated in terms of the well-known theories of heat conduction and of linear consolidation of a compressible soil. A moving boundary problem results, and closed form solutions have been obtained for several cases of practical interest. The results are presented in terms of normalized pore pressure distributions. It is shown that the excess pore pressures and the degree of consolidation in thawing soils depend primarily on the thaw consolidation ratio.

ISSN:0008-3674    

DOI:10.1139/t71-057

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Experimental investigations of passive earth pressures in sand show that current theoretical solutions overestimate failure loads and give incorrect stress distributions. Plasticity analysis has been used to examine the effects of changes in boundary friction and rotation preceding failure. Solutions have been developed to determine the magnitude of the scale effect due to the angle of shearing resistance of the sand varying with stress level in the failure zone. By assuming that the lower 30% of the wall does not reach plastic failure stresses, an assumption suggested by a recent experimental investigation, values of passive pressure coefficientKphave been calculated, which agree well with experimental values over a wide range of sand densities.

ISSN:0008-3674    

DOI:10.1139/t71-058

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Comparative drained triaxial tests at high confining pressures were carried out on a strong- and weak-grained granular material with 'rough' and 'lubricated' ends. The results indicated that the stress-strain relationships are significantly influenced by the end conditions. The use of 'lubricated' ends for high pressure tests results in much more uniform distribution of stress, strain, volume change, and crushing of particles throughout the samples.

ISSN:0008-3674    

DOI:10.1139/t71-059

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

A finite element method is employed to analyze the stress distribution along a steel anchor bolt grouted into rock. Penetration of the yielded zone into the grout wall and redistribution of stresses with increasing load are illustrated. The effect of varying modular ratio in a two-material system subjected to tensile loads is also illustrated.

ISSN:0008-3674    

DOI:10.1139/t71-060

出版商:NRC Research Press    

年代:1971

数据来源: NRC

摘要:

Severe land subsidence has been observed in a residential area in Ottawa built some 15 to 20 years ago on marshland. Subsidence varies from 12 to 18 in. (30 to 45 cm), affecting streets, sidewalks, driveways, fences, garages, and other structures supported on the ground surface. Houses were not affected because they were founded on shallow bedrock. Accelerated decomposition of the peat and the underlying marl is believed to have started when the area was drained for development, and this is believed to be responsible for the severe subsidence observed.

ISSN:0008-3674    

DOI:10.1139/t71-061

出版商:NRC Research Press    

年代:1971

数据来源: NRC