摘要:

Field evidence in Saskatchewan indicates that glaciotectonic processes result in a significant change in the shear strength properties of the sediments and the boundary conditions for the groundwater regime. Glacier ice-thrusting resulting in the deformation and shearing of bedrock and glacial sediments appears to be widespread throughout southern Saskatchewan and probably elsewhere where continental glaciers overran clay shale or weakly cemented bedrock. Theoretical considerations indicate that wherever a glacier is forced into compressive flow by physical features that tend to decrease flow downstream, shearing thrust planes develop in the ice causing brecciation, slickensides, overthrust faulting, and drag folding of sediments that have been carried up into the ice. The conditions required to produce this phenomenon include upslope movement of the glacier over a concave surface and net ablation in the glacier regime. Three examples of the engineering implications of this process are included where massive landslides were found and it was established that ice-thrusting had occurred. Criteria were then established that would enable geotechnical engineers to identify the presence of this phenomenon during site investigations.

ISSN:0008-3674    

DOI:10.1139/t78-051

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

This paper reports on observations of frost penetration into glacial till in a region of high freezing indices. The frost penetration measurements were carried out in borrow areas and in exposed dyke crests. The locations are far enough apart to be representative of regional frost penetrations. The frost susceptibility of the till is evaluated, and the effect of frost penetration on the design of freeboard and crest detail requirements for the dams and dykes is discussed. The geotechnical properties of the till are given along with the results of a series of surcharged cyclic freeze–thaw and thermal conductivity tests.The use of standard frost susceptibility criteria indicates that the till is classified as being highly frost susceptible; however, if surcharge pressure is considered and recognized as being a factor in reducing frost heave, then the till under field conditions may behave like a material of low frost susceptibility.

ISSN:0008-3674    

DOI:10.1139/t78-052

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Laboratory measurements of adfreeze strength of Ottawa fine sand to three different types of model piles under constant rates of loading are reported in this paper. Adfreeze strength,f, at peak load increased with increasing loading rate (i.e., rate of displacement of cross-head of the testing machine),İ, and followed a power lawThe maximum adfreeze bond strength developed with uncoated wood piles (B.C. fir and spruce). Concrete piles developed adfreeze bond strengths lower than wood but higher than steel and coated piles. Coatings (creosote, paint, etc.) reduced adfreeze bond strength considerably. In decreasing order of adfreeze bond strength, the piles rated as follows: uncoated B.C. fir, uncoated spruce, concrete, unpainted steel cylindrical and H-sections, creosoted B.C. fir, and, finally, painted steel pipe

ISSN:0008-3674    

DOI:10.1139/t78-053

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

This paper summarizes the results obtained with triaxial tests made on an unsaturated loam. The originality of the tests proceeds from the use of a Peltier effect psychometric probe for the measurements of interstitial pressure. This had made it possible to study the variations of the breaking stress in terms of water content and suction of soil. The coefficient χ of Bishop at rupture was also studied in terms of those variables and of the degree of saturation. An experimental relation between χ and |s| is proposed.

ISSN:0008-3674    

DOI:10.1139/t78-054

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

In September 1974 a large landslide occurred about 48 km northeast of Wainwright, Alberta. This failure presented features of interest but preslide conditions could not be reliably determined. Immediately south of this landslide a scarp some 150 m long and 0.6 m high had formed, probably contemporaneously with the failure. Field inspection suggested that this incipient failure was a sufficiently independent feature to merit detailed investigation. The major failure was termed the North Slide and the incipient failure was termed the South Slide. Collectively these slides make up the Edgerton Landslide.The failure occurred largely in flat lying, poorly indurated interbedded sandstones, siltstones, and clay shales of late Upper Cretaceous age which are overlain in the upland areas by a thin veneer of till of Wisconsin age. In the vicinity of the landslides there are many old slump areas much subdued by erosion. Field evidence indicated that the lower part of the recent failure surface had reactivated an old failure surface, whereas the scarp area represents a first time slide.The South Slide was investigated by boreholes and test pits. Samples were obtained for laboratory testing and piezometers and tiltmeters were installed in selected boreholes.The scarp increased in height and by May 1976 it was 2.3 m high. There was no sign of a toe cropping out down the slope; however, the tiltmeters became closed off successively in a downhill direction. There is strong evidence to suggest that failure is progressing from scarp to toe.Analyses of the failure indicate residual angles of shearing resistance were being mobilized along the outer pre-sheared part of the failure surface due to old landslides. The recent slip surface comprises an inward extension of this old surface and an upward portion rising at an angle of about 55° to meet with the known scarp. Along this latter portion of the recent failure surface the soil parameters yielding the most reasonable factor of safety are a peak angle of shearing resistance and a cohesion very much less than that determined from laboratory testing.It is postulated that the failure occurred due to a gradual loss of soil strength, manifested by a virtual disappearance of cohesion, with the final triggering mechanism being a springtime rise in the pore pressure within the slide mass. Factors involved in the strength loss are suggested as including deep weathering during the Tertiary, valley rebound, and old landslide activity.

ISSN:0008-3674    

DOI:10.1139/t78-055

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

This paper presents a method, based on inclinometric and moment measurements, to determine automatically the bending moments and the differential pressures in cast-in-place or sheet pile walls. A mathematical model using the polynomial least-squares approximation is proposed with a computer program developed for that purpose.The results and conclusions are illustrated by two examples. It is clearly shown that we can get the distribution curve of moments even for very inaccurate data. In most cases, the curves of dfferential pressures are significant. However, in the case of uncertain data, measures of bending moments are essential even in limited number. [Journal translation]

ISSN:0008-3674    

DOI:10.1139/t78-056

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Two methods of laboratory measurements of time-dependent deformations of rocks due to the relief ofinsitustresses are described. Experiments were performed on specimens taken from seven rock formations in southern Ontario. It was found that some rock types exhibit considerable time-dependent deformation, generally consistent with observed field behaviour. In addition, the swelling behaviour of the shaly rocks is anisotropic and constituent layers of the same rock formation may possess very different swelling characteristics. Mineralogical tests performed showed that the observed swelling behaviours are related to the composition and clay fabric of the rock.For detailed analysis of the test results, a rheological model was employed to represent the time-dependent deformation. Model parameters for three rock types have been obtained.Because the tests are simple and inexpensive to perform, it becomes practical to carry out a large number of tests for the evaluation of potential problems due to time-dependent deformation.

ISSN:0008-3674    

DOI:10.1139/t78-057

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The objective of this report is to present simulation analyses of heat and water flow during soil freezing. The analyses utilize a modified form of a model presented by Harlan. The model is tested by using experimental data reported by Dirksen and Miller and Jame and Norum. The basic elements of the model are the heat and water flow equations. An implicit finite-difference scheme is used to solve these two equations for the boundary conditions used in the experiments. The agreement between simulated and experimental results is illustrated for temperature, water, and ice contents.

ISSN:0008-3674    

DOI:10.1139/t78-058

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The Saint Jean Vianney landslide has redirected attention to soil studies conducted in 1941, as part of the site investigation program for the adjacent wartime Shipshaw power project. These included early studies of Leda clay, the sensitivity of which was recognized but not fully appreciated nor understood. Buried organic matter was encountered at one dam site. The possibility of landslide action accounting for the unusual position of this material was discounted in 1941. Recent studies by LaSalle have demonstrated the existence of a massive ancient landslide adjacent to the Shipshaw site. Earth movement resulting from this old landslide could explain the organic stratum. Carbon-14 dating suggests a date for this massive landslide that agrees with historical records of the great Quebec earthquake of August 1663. This caused earth movements of a magnitude not seen in Canada since that time, confirming the possibility of these being the explanation of the unusual position of the organic deposits. References to two papers on the Shipshaw studies, published in 1945, are given. Important corrections to conclusions contained in these papers are suggested.

ISSN:0008-3674    

DOI:10.1139/t78-059

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The ultimate bearing capacity of footings resting on subsoils consisting of two layers has been investigated for the cases of a dense or stiff layer overlying a weak deposit, and a loose or soft layer overlying a firm deposit. The analyses of different modes of soil failure are compared with the results of model tests on circular and strip footings on layered sand and clay soils.

ISSN:0008-3674    

DOI:10.1139/t78-060

出版商:NRC Research Press    

年代:1978

数据来源: NRC