摘要:

Acoustic signals scattered from the sea floor at nearly vertical incidence contain information about the physical properties of the sea floor. Signals may be decomposed into spatially coherent and spatially incoherent components the relative magnitudes of which are primarily a function of small scale bottom roughness. Experimental interping coherence functions derived on the basis of a linear system scattering model are shown to characterize contrasting sediment lithologies. The use of interping coherence as a sediment remote classification criterion and hence as a tracer of gross geotechnical properties is explored.

ISSN:0008-3674    

DOI:10.1139/t81-058

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

In previous work it has been shown that when a soil sample freezes in a one-dimensional manner under different cold-side step temperatures but the same warm-side temperature, at the formation of the final ice lens the water intake flux is proportional to the temperature gradient across the frozen fringe. The constant of proportionality has been called the segregation potential and this linear relation constitutes the coupling between heat and mass flow in a general theory of frost heave. This paper shows experimentally that the segregation potential is also a function of the average suction in the frozen fringe which is readily expressed in terms of the suction at the frost front. As a result it is also shown that measured water intake flux during freezing is dependent on the freezing path used to initiate the final ice lens. A thermodynamic explanation of the dependence of segregation potential on suction in the frozen fringe is also offered.

ISSN:0008-3674    

DOI:10.1139/t81-059

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A multi-device high density survey of the seafloor was conducted in the outer Placentia Bay area of Newfoundland using the Bedford Institute of Oceanography research ship CSSHudson. The acoustic records obtained from various systems, the seafloor soil samples collected by a piston corer and a grab sampler, and thein-situdata from a free-fall penetrometer were all subsequently analyzed. The correlation between the results of these different analyses is examined in this paper.

ISSN:0008-3674    

DOI:10.1139/t81-060

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The fundamental parameters of rock strength, rock mass stiffness, and interface roughness that control the development of side shear in a rock socketed pile are discussed on the basis of results from laboratory model socket tests, constant stiffness direct shear tests, and instrumented prototype piles. Based on the understanding of these fundamental parameters and on a survey of socket field test results, an empirical design method is proposed for side shear only sockets. This design method considers both the maximum load capacity and settlement criteria for single sockets.

ISSN:0008-3674    

DOI:10.1139/t81-061

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The ultimate bearing capacity of rigid vertical and batter piles and pile groups in layered sand has been determined under various inclinations of the load varying from the vertical to horizontal directions. The results of load tests on single model piles of different inclinations and on free-standing groups are compared with theoretical estimates. The influence of load inclination on the bearing capacity can be represented by simple interaction relationships between the axial and normal components of the ultimate load. The effect of eccentricity of the load on the ultimate bearing capacity of pile groups is discussed on the basis of previous theory and model test results.

ISSN:0008-3674    

DOI:10.1139/t81-062

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The problem of determining the holding capacity of flat plates and marine anchors in cohesionless soils is briefly reviewed and the reasons for the difference in the performance of marine anchors and that of simple flat plates are identified. The role which each anchor component plays during the embedment process is discussed.An analytical procedure to estimate the holding capacity of anchors with planar flukes, such as the Danforth anchor, as a function of soil properties and the depth of penetration into the soil is presented and checked against data from laboratory and published field tests.Factors such as anchor stability and characteristics of the pulling cable which can affect both anchor orientation and the maximum depth to which a particular anchor can penetrate the soil have not been included in the analysis. Consequently, it is not yet possible to predict the ultimate holding capacity that a particular anchor may achieve if pulled through an adequate distance.

ISSN:0008-3674    

DOI:10.1139/t81-063

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The approach embankment to the eastern extremity of a bridge across the East River near Trenton, Nova Scotia involved construction of a 6.4 m high embankment on tidal flats. Very soft to soft slightly organic marine silts were found to underlie the tidal flats to a depth of 6–9 m where bedrock was encountered. Construction of an embankment of this height on the tidal flats would require very flat sideslopes to ensure stability. Alternatively, all or part of the silt could be removed or the embankment could be built slowly using the stage loading technique and allow the silt to consolidate and gain strength during construction of the embankment. Stage loading had a considerable economic advantage over the other alternatives and since sufficient time was available, this method was adopted.The case history of this project is presented including results of the settlement performance of the embankment and porewater pressure response in the silt. These results are compared with predicted values and conclusions are drawn regarding the stage loading technique for this particular type of application.

ISSN:0008-3674    

DOI:10.1139/t81-064

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The excavation of mine pits in western North Dakota causes groundwater to flow laterally through the moderately to highly permeable fractured coal beds into the pits. Because of the low fracture-controlled storativity of the coal, the lateral flow results in rapid spread of a dewatered zone in the coal. The coal is generally overlain by saturated silty or clayey aquitards or fine sand that provide downward leakage to the coal. Existing analytical solutions for analysis of the problem of water-level decline and seepage flux are based on such extensive simplifying assumptions that they are a poor approximation of the field conditions. Numerical models for layered systems with transient saturated and unsaturated zones require efforts in analysis that are generally unwarranted relative to the nature of the field information. As an alternative to these approaches we applied a method based on existing analytical solutions with empirical adjustments to account for the effect of leakage. Results obtained using a programable pocket calculator indicating that, for areas for which mining is proposed, steady-state water levels in the coal will be rapidly attained as downward leakage through the overlying beds supplies all of the water maintaining the lateral flow regime in the coal.Predictions from analyses using representative values of hydraulic parameters for two mine sites indicate that significant declines in water levels adjacent to the mines will likely be restricted to within about 3 km of the highwall.

ISSN:0008-3674    

DOI:10.1139/t81-065

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The construction of an underpass in the City of Edmonton required the temporary relocation of the CNR main-line prior to the construction of a permanent bridge. The line was placed close to the underpass excavation which was supported by a tie-back sheet pile wall. Because of the stringent requirements associated with the presence of the railway line, the supports were designed on a conservative basis and observations of tie-back loads were taken over a period of 7 months.This note presents the observations of tie-back loads from January to July, 1977. Following installation in accordance with the design requirements, substantial fluctuations in tie-back load were observed for about 3 months. Then the loads fell off gradually to about 50% of the originally applied values. The variation of the load with time bears a strong correlation with average air temperature and is accounted for by the alternate freezing and thawing of the ground adjacent to the sheet pile wall. The ultimate decline in load is attributed to relaxation of the soil behind the wall during spring thaw. The case history draws attention to special requirements associated with interpretation of earth pressure measurements during winter con struction.

ISSN:0008-3674    

DOI:10.1139/t81-066

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Results of seepage analyses for two dams on semipervious foundations obtained with finite element techniques are presented in order to assess the relative effectiveness of seepage control elements in reducing the downstream exit gradient. After presenting results to illustrate the effect of permeability anisotropy, the effectivenesses of a downstream relief trench, an upstream impervious blanket, a partial cut-off, and a more pervious drain material are compared in terms of the factor of safety against piping at the downstream toe.

ISSN:0008-3674    

DOI:10.1139/t81-067

出版商:NRC Research Press    

年代:1981

数据来源: NRC