摘要:

The significance of a separation into elastic and slip components is considered for the case of particulate material. Tests on sand, including a variety of stress paths in a triaxial and a plane strain apparatus, indicate that for a majority of first-loading paths the total strains are closely given by the slip strains alone. The stress dilatancy theory is seen to provide a simple and accurate flow rule for predicting the slip strains.

ISSN:0008-3674    

DOI:10.1139/t69-026

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The results of a series of tests designed to examine the behavior of saturated clay soil under repeated loading are reported. Triaxial tests, under conditions of axial symmetry, were used and the rates of deformation were chosen so as to permit the accurate measurement of pore water pressure at all stages of the tests.It was found that, for any particular consolidation history, a critical level of repeated stress existed. Below this critical level, a state of nonfailure equilibrium was reached in which the stress-strain curves followed closed hysteresis loops. Above the critical level of repeated stress, effective stress failure occurred; and each cycle of loading produced cumulative increases in deformation.An interesting feature of the test results was that a linear relationship between the magnitude of the applied repeated stress and the increase in pore water pressure was found for stress levels below the critical value.

ISSN:0008-3674    

DOI:10.1139/t69-027

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The results of periodic pavement elevation and crack-width measurements taken over a period of three to four years are presented. Both surface elevation and crack-width changes are shown to follow a similar seasonal cycle. Results show that the sub-grades studied were frozen as closed systems. It is shown that with closed system subgrade freezing the resulting vertical displacement of the pavement may be either positive or negative depending on the moisture content of the subgrade. The negative case, corresponding to vertical freezing shrinkage, occurred with dry clay subgrades. For a given observation section, seasonal surface movements in a vertical direction are shown to vary from the traffic lanes to the shoulders. The difference is explained in terms of corresponding differences in the subgrade moisture conditions.Results are presented which indicate that seasonal changes in the width of transverse pavement cracks cannot be fully explained in terms of simple thermal expansion and contraction in the asphaltic concrete pavement. Indirect evidence is presented which suggests that horizontal freezing shrinkage in a subgrade contributes to the seasonal cycle of crack-width changes.

ISSN:0008-3674    

DOI:10.1139/t69-028

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Under field loading conditions, the consolidation of a clay layer is likely to take place under effective principal stress ratios (σ1′/σ3′), which vary from point to point throughout the soil mass. From a consideration of idealized stress paths, an estimate is made of the effect of stress ratio on rates of volumetric strain and excess pore water pressure dissipation. These predictions are partly supported by data obtained from anisotropic consolidation tests on Leda clay, the major disagreements being due to the significant influence of structural cementation on the rate process.The experimentally observed rates of shear strain have been analyzed in terms of stress-dilatancy concepts. The plastic strain-increment ratio was shown to be a unique function of effective stress ratio, thus confirming the validity of previous work on remoulded clays. A theoretical prediction of this relationship postulated by Burland (1965) did not approximate to the experimental data, due probably to the influence of secondary deformations. The data did, however, show a relationship similar in form to that derived by Walker (1969) for the secondary deformation of remoulded kaolin.

ISSN:0008-3674    

DOI:10.1139/t69-029

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The detrimental effects of driving sand drains in sensitive soils are discussed. Several case records of the behavior of embankments on such soils are analyzed. It is concluded that if a careful foundation investigation indicates the desirability of increasing the rate of primary consolidation, non-displacement sand drains should be used. It is also shown that sand drains of any type are of little or no value in soils that exhibit substantial secondary settlements.

ISSN:0008-3674    

DOI:10.1139/t69-030

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The heaving force transmitted to(7.6-cm) diameter steel pipes by adfreezing in Leda clay was measured in the field for two consecutive winters. The maximum uplift force was approximately 6000 lb (2700 kg), which corresponds to an apparent adfreeze strength of about 12.5 p.s.i. (≈ 0.9 kg/cm2). It developed gradually during prolonged periods of cold weather, but dropped off rapidly during warming trends, although the whole soil profile remained below 0 °C. Adfreezing did not retard frost heave in the soil in the vicinity of the steel pipes.Agreement between experimental values for maximum uplift forces by adfreezing and values predicted by Dalmotov's equation suggests that such predictions can be used as a guide for design purposes if no other information is availabl

ISSN:0008-3674    

DOI:10.1139/t69-031

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Three full-scale bored cast-in-place concrete piles constructed to give no tip resistance were loaded to failure using the equilibrium method of loading. Each pile was 24 inches (61 cm) in diameter, but of different length, stopping in turn in strata of partly saturated highly plastic clay, saturated silty clay, and till. Ultimate skin friction values were calculated and compared to direct shear tests, and laboratory and field vane tests giving values of undrained shear strength.There were large variations in shear strength results even at the same depth in adjacent holes. Comparison of vane tests on soil samples and on the surface of the bored hole showed disturbance caused by drilling to be negligible for these soils.Results from an interfacial friction de-vice lowered into the hole indicated that the skin friction increased with lateral stress and that the lateral pressure on the concreted piles at the time of testing was less than 10 psi (.7 kg/cm2).

ISSN:0008-3674    

DOI:10.1139/t69-032

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

As research is expanding into more detailed study of stress–strain behavior of soils in the triaxial test, it is necessary to develop new techniques for measuring more accurately loads and deformations. However, the necessary measuring equipment is not always available commercially. The writers have developed a transducerized apparatus to measure the diameter of triaxial samples, and information on the design and characteristics are presented in this research note.

ISSN:0008-3674    

DOI:10.1139/t69-033

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The paper reports a new pile-force gauge based upon the principle of the vibrating wire. The gauge is intended to be driven down with a precast concrete pile and can be placed at an arbitrarily chosen depth in the pile. The impacts from the pile driving will not impair the gauge. The gauge registers the static loads and bending moments in a pile with an error not exceeding 2% of the linear measuring range. This maximum error includes the drifting of zero point and change of sensitivity with time.The design of the gauge and laboratory and full-scale tests are reported, and suitable use of the gauge is suggested.

ISSN:0008-3674    

DOI:10.1139/t69-034

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The paper describes an apparatus for determining vertical settlements by measuring the hydrostatic pressures in a flexible fluid-filled hose positioned horizontally beneath an engineering structure. The pressures are measured with a torpedo containing a pressure transducer which is pulled through the hose, enabling settlements to be measured continuously along its length. As it is withdrawn after each survey, it can be used for any number of installations.

ISSN:0008-3674    

DOI:10.1139/t69-035

出版商:NRC Research Press    

年代:1969

数据来源: NRC