摘要:

Coal mining in Lethbridge began in 1872 and continued until 1965. Workings were by underground room and pillar techniques on a single near-horizontal seam. Parts of the city, and particularly the recently developed or soon to be developed areas, to the north and west of the city, are underlain by mine workings. This has necessitated comprehensive geotechnical investigations to evaluate potential subsidence hazards and to enable guidelines for construction precautions to be developed. Because of the relatively uniform conditions throughout the area, the borehole data accumulated during these investigations illustrate well some aspects of the process of mining subsidence above abandoned workings. Another interesting aspect of the Lethbridge case history is the phenomenon of soil cracking that occurs around the edge of worked seams. Even though calculated potential tensile strains are small, it appears that they can be concentrated to form thin cracks in the very stiff, unsaturated overburden soils. These cracks can subsequently be exploited by surface erosion processes and result in voids or soft zones, which are a potential hazard to construction.Key words: mining subsidence, void migration, soil cracking, development guidelines.

ISSN:0008-3674    

DOI:10.1139/t88-086

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The role of analysis in the evaluation and design of barriers is discussed. Factors considered include (i) the mechanisms controlling contaminant migration through barriers; (ii) the determination of diffusion and distribution coefficients; (iii) leachate mounding and the effect of clogging of leachate collection systems upon contaminant migration through barriers; (iv) the importance of considering the finite mass of contaminant available for transport into the soil and a method of modelling the effect of finite mass of contaminant; and (v) examples of how analysis may improve the geotechnical engineer's feel for the effectiveness of potential contaminant attenuation mechanisms in both glacial till deposits and fractured rock.Key words: contaminant migration, analysis, diffusion, advection, clays, groundwater, fractured rock, design, barriers.

ISSN:0008-3674    

DOI:10.1139/t88-087

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The rheological behavior of some sensitive clays has shown that there are positive relationships between plastic viscosity, yield stress, remolded shear strength, and liquidity index. Based on the various correlations, remolded strength values can be predicted for soils with a liquidity index as high as 6. For a liquidity index varying from 2 to 5, the remolded undrained shear strength and plastic viscosity vary from about 90 to 5 Pa and from 200 to 7 mPa∙s respectively. It has been observed that most sensitive clays behave either as a Bingham or a Casson fluid, the latter behavior being related to less sensitive clays of higher pore-water salinities. Increasing the salt content from 0.5 to 30 g/L modified the rheological behavior of a single test soil from that of a Bingham to that of a Casson type of fluid. Such modification in the pore-water salinity illustrates how soils can have similar plastic viscosity and similar remolded strength but different yield stresses. The range of viscosity measured for sensitive clays is very different from that of values obtained from back analysis of subaerial or submarine slides where viscous flow can be expected.Key words: sensitivity, clays, viscosity, yield stress, shear strength, salinity, liquidity index, submarine slide, landslid

ISSN:0008-3674    

DOI:10.1139/t88-088

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

The effect of temperature on the volumetric strains of the clay skeleton and clay – water system has been examined experimentally. Heating tests at (various) constant effective stress and isotropic loading tests at (various) constant temperatures were performed on low-porosity clays under drained conditions. The results indicate that the thermal expansion of adsorbed water in these clays is significantly lower than that of free water. Depending on the effective pressure, the clay skeleton may undergo either compression or expansion.Key words: nuclear waste isolation, clay, low porosity, thermal strain, adsorbed water.

ISSN:0008-3674    

DOI:10.1139/t88-089

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

This work presents the construction procedures and pile load test results of large-diameter bored and grouted cast-in-place concrete piles in coral formations and carbonate sediments in the Red Sea. Construction details and difficulties involved in the process of site preparation, borings, reinforcement, concrete casting, and grouting are described and discussed. Geotechnical engineering considerations that led to the selection of this type of foundation and the conditions of the site are included.Key words: pile foundations, bored and grouted, marine sediments, construction methodology, load testing.

ISSN:0008-3674    

DOI:10.1139/t88-090

出版商:NRC Research Press    

年代:1988

数据来源: NRC

摘要:

Soft, intertill, glaciolacustrine clays are of concern for stability of slopes and foundations. An intertill clay deposit between 32 and 54 m below the surface was continuously cored. Index properties were determined for 46 samples and 10 samples were tested on the oedometer. Stratigraphic evidence indicates that the glaciolacustrine clay (Blaine Lake Member), lying between the till of the Sutherland and Saskatoon groups, was glaciated three times. However, preconsolidation pressures of this intertill clay show the degree of consolidation is less than 20% based on a total stress from an estimated ice thickness extrapolated from the Cypress Hills. This low preconsolidation pressure suggests there was insufficient time for dissipation of excess pore-water pressure created by thickening of the advancing glacier.Key words: preconsolidation pressure, excess pore-water pressure, glaciers, intertill clay.

ISSN:0008-3674    

DOI:10.1139/t88-091

出版商:NRC Research Press    

年代:1988

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t88-092

出版商:NRC Research Press    

年代:1988

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t88-093

出版商:NRC Research Press    

年代:1988

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t88-094

出版商:NRC Research Press    

年代:1988

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t88-095

出版商:NRC Research Press    

年代:1988

数据来源: NRC