摘要:

This paper presents results from a field investigation in which groundwater pressures were measured in a natural slope of soft clay over a 10 year period. Measurements of piezometric levels are reported together with calculated annual changes of safety factor of the slope.Using consolidation theory, predictions were made of changes of piezometric levels for the condition of zero infiltration based on the postulate that these changes were the direct result of changes of hydraulic conditions at the ground surface. The predictions were in agreement with the field measurements.A method is suggested for estimating the most severe groundwater pressures that a clay slope can be expected to experience. Using this method, estimates were made of the minimum expected value of safety factor of the slope at the test site.Keywords: natural slope, clay, pore pressures, field measurements, stability, long-term.

ISSN:0008-3674    

DOI:10.1139/t84-011

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The C.W. Intake Tunnel of the Darlington Nuclear Station is D-shaped in section with a span of 8 m and a length of 925 m beneath Lake Ontario. The tunnel is located in a horizontally bedded limestone with variable shaly interbeds.The geotechnical investigation includingin-siturock stress measurements, and laboratory determination of strength and deformation properties as well as time-dependent behaviour are reported. Design of the tunnel, in particular provisions for "rock squeeze," is described in detail.To verify the design approach adopted and the provisions made, field instrumentation was performed during excavation of the tunnel. The results of field measurements of stresses and displacements were compared with premonitoring analysis. Postmonitoring analyses were also performed using the as-constructed condition. It is shown that the performance of the tunnel is in general agreement with the predicted behaviour in both short and long term conditions.Keywords: stress, displacement, time-dependent deformation, stressmeter, tunnel, rock mechanics, rock squeeze.

ISSN:0008-3674    

DOI:10.1139/t84-012

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The calculation of the lateral earth force using the limit equilibrium method of slices is an indeterminate problem. An assumption regarding the direction or the magnitude of certain forces, or the position of the line of thrust can be used to render the problem determinate.A general formulation for the lateral earth force is derived in accordance with the assumptions involved in the general limit equilibrium (GLE) method. An assumption concerning a direction of the interslice forces is utilized to solve the problem of indeterminancy. Horizontal force equilibrium conditions within a sliding mass are used to compute the magnitude of the active and passive forces. The point of application of the lateral earth force is obtained by considering moment equilibrium for each slice.The coefficient of lateral earth force obtained from the GLE method agrees closely with the results obtained from most other theories. Comparisons are made to the Coulomb theory (i.e., using a planar slip surface) and other theories using a curved or a composite slip surface.Data are presented for the case of a horizontal cohesionless backfill against a vertical wall. The lateral earth force can be contoured on the grid of centers of rotation. These contours have a bell-shaped characteristic and can be used to locate the critical center of rotation.The main advantage of this method lies in its capability to analyze arbitrarily stratified soil deposits with complex geometries. Different conditions of pore-water pressure, shear strength, and external loading can be accommodated in the analysis. Factors of safety greater than 1.0 can be applied to the shear strength of the soil for design purposes.Keywords: lateral earth force, active force, passive force, general limit equilibrium, interslice forces, and coefficient of lateral earth force.

ISSN:0008-3674    

DOI:10.1139/t84-013

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A commercial acoustic emission monitoring system (Model MS-1 Geo-monitor) was used to record acoustic emissions in undisturbed block samples of Champlain Sea clays that were deformed to a passive failure state in the laboratory. Laboratory cast samples of Ottawa sand, washed concrete sand, remoulded kaolin clay, and remoulded Champlain Sea clay were also used in order to correlate the acoustic response of various soils. The Geo-monitor system was capable of detecting and quantifying acoustic emissions in all soils tested. Acoustic emissions associated with failure in the coarse-grained soils ranged from 50 to 200 emissions per minute at an amplification of 1000 times. In the fine-grained soils, an amplification of 105times was required and acoustic emissions of up to 25 emissions per minute were recorded under passive failure conditions.Keywords: acoustic monitoring, slopes, sensitive clay, laboratory study.

ISSN:0008-3674    

DOI:10.1139/t84-014

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Samples from four surface and one subsurface horizons of clay-rich soils from Quebec were air-dried and critical point dried. In the latter samples, the total pore volume was 19–84% larger than in the former samples. The total pore volume, determined by mercury intrusion porosimetry and density measurements, was subdivided into large (> 8.8 μm), medium, and small (< 0.19 μm) pores. The effect of drying on these pores was estimated. Medium-sized pores were affected most by the drying technique, followed next by the large pores, and finally by the small pores. The modifications due to drying could not be explained adequately by shrinkage and it was assumed, from the pore-size distribution curves, that organic matter content had a buffer effect on particle reorganization.Keywords: critical point drying, clay soils, pore volume, pore-size distribution, organic matter.

ISSN:0008-3674    

DOI:10.1139/t84-015

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The addition of cement to a bentonite slurry gives a complex material called self-hardening grout which slowly sets to become a clay-like solid. The properties of these mixes are highly dependent on the bentonite and the cement used. Most information available up to now comes from European countries where the technique has been developed. As very little information was available about such mixes in North America, an experimental program was initiated to study their applicability for cutoff walls of certain dams of the James Bay hydroelectric project. The present paper describes the characteristics of different mixes tested in their fluid and solid states.Keywords: bentonite, cement, slurry, cutoff wall.

ISSN:0008-3674    

DOI:10.1139/t84-016

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A one-dimensional analytical model has been proposed for the average quasi-static snow creep pressure parallel to a slope at the centre of a long rigid structure. The model includes forces due to interruption of creep (internal deformation) and glide (slip of the snow cover over the ground). In reality, the problem is two-dimensional. By a series of two-dimensional finite element calculations, an empirical analytical correction has been found to improve the model. This yields a simple analytical model that provides results within 6% or less of the more complex two-dimensional problem.Keywords: snow mechanics, creep, glide, snow pressure, snow-pack, finite element.

ISSN:0008-3674    

DOI:10.1139/t84-017

出版商:NRC Research Press    

年代:1984

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t84-018

出版商:NRC Research Press    

年代:1984

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t84-019

出版商:NRC Research Press    

年代:1984

数据来源: NRC

ISSN:0008-3674    

DOI:10.1139/t84-020

出版商:NRC Research Press    

年代:1984

数据来源: NRC