摘要:

The screw plate test was developed for the determination of theinsitudeformability characteristics of both granular and cohesive soils. This paper examines several theoretical models that may be used to evaluate theinsituundrained deformability and shearing strength characteristics of a cohesive soil medium from results of screw plate tests. It is shown that the undrained modulus and the undrained shearing strength can be evaluated directly from the load–displacement response obtained from the screw plate test.

ISSN:0008-3674    

DOI:10.1139/t80-055

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

This study reveals that a freezing soil can be characterized by two parameters, the segregation-freezing temperatureTsand the overall permeability of the frozen fringe. During unsteady heat flow, the variation of these parameters with temperature produces rhythmic ice banding in fine-grained soils. At the onset of steady-state conditions, freezing tests conducted at a fixed warm end temperature showed thatTswas independent of the cold side step temperature. In addition, a model is presented that indicates how the overall permeability of the frozen fringe can be calculated without detailed measurements at the scale of the frozen fringe. It is also constant in the tests reported here.

ISSN:0008-3674    

DOI:10.1139/t80-056

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

In arctic regions mass movements in thawing permafrost are common. Although different types of landslides have been identified, one type referred to as a "bimodal flow" has caused a significant amount of interest on account of the unusually high rate of mass wasting associated with this type of flow slide. The flow is characterized by a steep headscarp and a low angle mud flow or tongue at the base of the slide.Although more than one activity contributes to the retreat of the headscarp, the most important process is that of ablation. An obvious anomaly exists between the amount of heat required to sustain the high rates of observed ablation and the amount of heat available from net radiation.The components of the energy balance were identified and a field study was undertaken to quantify these terms. Instrumentation included radiometers, wet and dry thermocouples, anemometers, and a lysimeter to measure the latent heat of condensation of evaporation.The results of this study indicate that all the major terms in the energy balance equation combined to form the source of heat responsible for the high rates of observed ablation. Moreover, they provide a rational basis for controlling bimodal flow slides using different insulation materials.

ISSN:0008-3674    

DOI:10.1139/t80-057

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The importance of disturbance and remoulding to the alteration of mechanical properties of sensitive soils has been well documented in the geotechnical literature both in terms of laboratory and field behaviours. Man-made transient dynamic input such as dynamite blasting, heavy vehicles, and train movement have been suspected of being capable of causing a reduction in theinsitustrength parameters of sensitive clays. A laboratory test program was undertaken to determine whether dynamic loading at peak stress levels below normal failure strength caused similar changes in the mechanical properties, and specifically to quantify the phenomena.In order to simulate highly overconsolidated conditions most of the tests were carried out under conditions of no confining pressure, although supplemental data were obtained from consolidated undrained tests. Some of the variables examined in this program were confining pressure, mean deviatoric stress, cyclic deviatoric stress, cyclic strain, number of applications, frequency, and reference strength. In order to compare the effect of dynamic input with the long-term creep phenomena, a simultaneous constant load program was undertaken.In general terms, the study indicates that under the prestated laboratory test conditions no major reduction in peak strength was found under dynamic loading, and that failure would occur at comparative stress levels under dead-load conditions, but required a greater time. In addition, examination of the sample after failure revealed that any remoulding of the sample appeared to be restricted to the area adjacent to the shear zone.

ISSN:0008-3674    

DOI:10.1139/t80-058

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Using data contained in theMackenzie Valley Geotechnical Data Banktogether with data derived from morphometric analyses of topographic maps and air photographs, the volume of ground ice present in the upper 10 m of Richards Island is calculated to be 10.27 km3. Pore and segregated ice constitute over 80% of the total ice volume. Wedge ice constitutes between 12 and 16% of total ice volume in the upper 4.5 m, and approximately 36% of all excess ice. In the upper 1–2 m, wedge ice may exceed 50% of earth materials. Pingo ice is insignificant in terms of its contribution to total ice volumes. Excess ice constitutes 14% of the upper 10 m of permafrost; it follows that thawing of this layer of permafrost may lead to an average subsidence of 1.4 m.The results of this study are probably typical of other areas of the Pleistocene Mackenzie delta. There is also general agreement with data obtained from arctic Alaska.

ISSN:0008-3674    

DOI:10.1139/t80-059

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The filtration performance of nonwoven thick synthetic fabrics used in soil stabilization, erosion control, and earth reinforcement is predicted from a proposed analytical method. The morphological analysis of many fabrics has been utilized to identify internal structure parameters responsible for their hydraulic properties and to predict percentage retention of soil particles in the analysed fabrics. Experimental data indicated a relationship between the water permeability and the fiber density of a fabric. Furthermore, data are given to enable one to predict the percentage retention of particles from fiber density.

ISSN:0008-3674    

DOI:10.1139/t80-060

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The new approach to the stability analysis of embankments on sensitive clays, which is presented in this paper, is based on an interpretation of Bjerrum's data made by Mesri, which led to the observation that the available strength at failure under an embankment is nearly independent of the plasticity index and is a function of the preconsolidation pressure of the clay deposit. The new method is found to give good results in sensitive clays, but does not seem to be applicable to soft layered organic, cohesive soils.

ISSN:0008-3674    

DOI:10.1139/t80-061

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Single point resistance and spontaneous potential geophysical borehole logging is shown to be a valuable supplement to conventional coring methods in geotechnical site exploration. A continuous graphical record of the sediments is obtained without gaps caused by sample recovery problems. The log provides an effective capability for stratigraphic correlation. The technique is also shown to be of value as a format for a borehole data base and for use in instrumentation design such as piezometers and observation wells. The technique has limitations such as drift and maintenance difficulties but these can be overcome by adequate field supervision. Over 7000 testholes have been logged successfully and are in data storage in Saskatchewan.

ISSN:0008-3674    

DOI:10.1139/t80-062

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Recent tests have examined the properties of block samples and tube samples from depths to 12 m in Winnipeg clay. Careful trimming and a wide variety of testing procedures have permitted new insights into the behaviour of the clay that is markedly anisotropic and non-homogeneous. The effective strength envelope for "blue clay" from 6 to 12 m depth can be simplified into three straight-line sections. At low stresses, a section of the envelope has been identified having a low cohesion intercept and a high "friction" angle. This is thought to be caused by close Assuring in the clay, and controls the field behaviour in many small embankment, riverbank, and excavation problems. Atinsitustress levels, the clay dilates markedly as failure is approached. Porewater pressures depend strongly on stress levels during laboratory reconsolidation. Residual strengths are low, and are influenced by the methods used during testing. Yielding has been clearly identified for shear failure of the grain structure, but is more poorly defined for increasing normal octahedral stresses. The work has emphasized the importance of selecting appropriate testing procedures and stresses for field applications.

ISSN:0008-3674    

DOI:10.1139/t80-063

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The method of control of water in open excavations by pumping from sumps, from deep wells, or from well points is such an accepted practice that sometimes little attention is given to its complex and difficult hydraulic nature.This paper describes the causes leading to a hydraulic failure of a 15 m deep temporary sheeted cofferdam required to found a concrete slab for a pump house. The construction of the new pump house was for the extension of facilities of a sewage treatment plant. The piping failure caused a considerable construction delay and it also served as a field case to reassess the construction procedure of the excavation and the inadequacy of the well point installation.

ISSN:0008-3674    

DOI:10.1139/t80-064

出版商:NRC Research Press    

年代:1980

数据来源: NRC