摘要:

The Denholm landslide, whose surface is composed of scarps, ridges, and elongated depressions, is 160 m high, 2000 m wide, and up to 100 m thick. The shear zone is in silty, montomorillonitic clay of the upper part of the Lea Park Formation and Upper Colorado Group unit. The Upper Cretaceous Judith River Formation and the Quaternary Empress, Sutherland, and Saskatoon groups were affected by the landslide. Although these sediments were fractured and gravity faulted by tension when the landslide moved, they can be readily traced through the landslide, particularly the upper part. The scarps (gravity faults), ridges (horsts), and elongated depressions (grabens) are the surface expression of tension resulting from the stretching of beds during the landslide.The movement of the landslide is thought to have started when the North Saskatchewan spillway eroded to the level of the present shear zone about 11 000 years ago (established by radiocarbon dating) and is believed to have stopped in recent time. During this time, it moved about 390 m across the North Saskatchewan River alluvium at an average rate of 35 mm per year. As the landslide moved across the valley, it encountered deposition of alluvium at an average rate of about 2.4 mm per year which resulted in the curved shear zone on the alluvium.Keywords: retrogressive landslide, shale-alluvium, displacement, rate, age.

ISSN:0008-3674    

DOI:10.1139/t83-024

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

A procedure incorporating geological evidence with analytical methods was developed for the back analysis of a multiple retrogressive landslide in Cretaceous clay shale. The slide mass, apparently inactive, extends 2 km back from the toe at the river and is seated on a shear zone 100 m deep at the main scarp. Historical evidence of the slope movement was established from radiocarbon dating of the river alluvium over which the landslide moved. The geometry of the landslide when the factor of safety was near unity was determined from historic and stratigraphic evidence and sensitivity analyses.The stratigraphy of the slide mass showed that the beds are stretched with very little vertical displacement, indicating a mainly translational mechanism along a nearly horizontal shear zone. Apparently movement has taken place at a slow but steady rate over 11 000 years, resulting in a horizontal displacement of 390–430 m at the toe. The landslide, therefore, was analyzed as a series of sliding blocks with a common failure surface retrogressing from the toe up to the scarp. Each successive block was combined and considered to be moving as a single unit. Unknown factors, such as pore-water pressure at failure and the influence of cohesion, were evaluated by sensitivity analyses. The effective angle of shearing resistance required for limiting equilibrium was relatively constant, ranging from 7.6 to 8.7°, assuming the water table to be near the ground surface. For a lower water table, the values ranged from 6.5 to 8.0°. The equivalent values of cohesion required for equilibrium withranged from 42 to 82 kPa depending on the size of the block, suggesting thatc′ must be zero for the retrogressive mechanism analyzed by combining successive blocks.Keywords: slope stability, multiple-block, back analysis, residual strength, sensitivity analysis.

ISSN:0008-3674    

DOI:10.1139/t83-025

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

Determination of the true orientations of fractures in diamond drill cores obtained from deep boreholes in plutonic bodies is an essential requirement of the geoscience component of the Canadian Nuclear Fuel Waste Management Program. A reference line can be painted on the entire length of the rock core, indicating the orientation of the core, and the apparent orientation of the fracture can be measured from this reference line. This paper describes three methods that have been developed to convert the apparent orientation to true orientation, namely, stereographic projection, spherical trigonometry, and analytical geometry. The results obtained from these techniques were compared to assess their relative accuracy. Whereas the graphical method is more readily adaptable for use in the field, the mathematical methods can be computer-programmed and the programs GEOCORE and ORIENTC are available from the Geological Survey of Canada to facilitate the calculation of large volumes of data.Keywords: true orientation, fracture, rock core, stereographic projection, spherical trigonometry, analytical geometry.

ISSN:0008-3674    

DOI:10.1139/t83-026

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

Lateral earth pressures produced by saturated clays with negative pore-water pressures and unsaturated expansive clays with positive matric suctions are considered from a theoretical standpoint. Simple earth pressure equations are formulated in terms of total stresses using the Mohr–Coulomb failure criteria and the assumptions consistent with the Rankine earth pressure theory.Conventional practice is to separate the pressure that the soil exerts on the wall into the pressure produced by the soil structure (effective stress) and that produced by the water (neutral stress). Since two stress state variables are required to describe the behavior of unsaturated soils, the expressions can no longer be separated into two distinct components.The change in lateral pressures resulting from decreases in pore-water pressure or increases in matric suction are quantified by considering a 6 m high wall for the active and passive cases. Tension cracks are shown to have little effect on the conditions shown.The magnitude of the lateral pressure generated due to changes in matric suction under conditions where walls are restrained from moving depends upon the ratio (KT) of horizontal to vertical stress and the matric suction of the backfill at the time that it is placed behind the wall. When structural members are cast directly against undisturbed clays, similar criteria govern the magnitude of the lateral pressures that may be generated due to changes in matric suction. The maximum pressure that can be developed in some cases will be equal to the passive pressure of the soil when it is saturated.An expression for the critical height of a vertical bank for the saturated and unsaturated cases is developed. The role of tension cracks is shown by computing the critical height of a vertical slope for a typical soil both in the absence and in the presence of tension cracks.In many instances it is apparent that methods devised to sustain the matric suction at or near its original value may result in a substantial savings in design or that they will ensure adequate performance standards for existing facilities.Keywords: Lateral earth pressure, active pressure, passive pressure, unsaturated soils, expansive soils, tension cracks, retaining walls, unsupported excavations.

ISSN:0008-3674    

DOI:10.1139/t83-027

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

This article describes different forms of surface displacement observed in association with faulting in the earthquake zones of Tangshan (Hebei Province of north China) and the southern part of Liao Ning Province. Shallow surface fractures appear to have only a limited effect on nearby surface and subsurface structures, but fractures that overlie deep faulting cause breakage of most surface structures. Shallow surface fractures tend to parallel the alignment of main shock and aftershock epicentres but may be displaced by some considerable distance from the alignment of such movements. The mechanisms linking seismic shock and displacements by shallow surface fractures require further investigation.Keywords: faulting, surface displacements, China.

ISSN:0008-3674    

DOI:10.1139/t83-028

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

As a chilled pipeline crosses a transition from frozen to unfrozen ground or shallow permafrost, a differential frost heave problem may develop causing strains in the pipe. Soil–structure interaction models that are currently available to handle this problem concentrate on the pipe as the dominant structural member and represent the soil mass as a series of unconnected springs. This paper considers the soil to be an elastic or nonlinear viscous continuum and imposes a nonlinear boundary condition to represent the frost heaving soil and the dependence of frost heave on applied pressure. The pipe is assumed to be a completely passive structural member and the soil strains at the pipe elevations are studied. The dependence of the maximum pipe strains on the length of the heaving section and on the thickness of frozen ground beneath the pipe have been established for a typical set of soil and frost heaving conditions. It is found that, for the conditions studied, when the thickness of shallow permafrost or frozen soil is greater than about 7–8 m, the strains that a flexible pipe experiences are less than the strain criteria currently in use on many pipeline projects.Keywords: frost heave, pipeline, interaction, stress analysis, finite elements, continuum mechanics, thermo-elasticity.

ISSN:0008-3674    

DOI:10.1139/t83-029

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

Amoco International Oil Company and the government of Trinidad and Tobago have formed a consortium (FERTRIN) to construct and operate two ammonia plants. The site is located on the west coast of Trinidad some 32 km south of Port of Spain and is part of a major industrial development being planned by the government.Trinidad is located in one of the most seismically active regions of the Caribbean. Local building codes are still in the process of development, but local practice requires design specifications similar to the highest risk earthquake zones in California. As a result, piling under critical and heavy structures is often governed by the lateral rather than the vertical load requirements.This paper describes the choice, design, and performance of the piles tested for the FERTRIN ammonia plants. The design methods are evaluated and predictions of both lateral and vertical pile performance are compared with the load test results.Keywords: piles, lateral loads, axial loads, load tests, foundations, load transfer.

ISSN:0008-3674    

DOI:10.1139/t83-030

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

Rock wedges in the roofs of underground excavations may be wholly or partly self-supporting due to the mobilization of shear resistance on discontinuities bounding such wedges. The extent of the mobilization, which occurs as the wedge deforms, is markedly influenced by the magnitude of the stress field tangential to the opening and the relative stiffness of the intact rock and the shear and normal stiffnesses of the discontinuities. Analytical and numerical models are described for determining the upper and lower bounds of the failure loads for two-dimensional asymmetric and symmetric rock wedges. Experiments conducted on physical models indicate that the stability of rock wedges may be substantially reduced by loosening and that the analytical solutions may overestimate the load necessary to cause failure.Keywords: rock wedge stability,in situstresses, joint stiffness.

ISSN:0008-3674    

DOI:10.1139/t83-031

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

The geologic and geotechnical characteristics of thick soft Champlain Sea clay deposits at Hawkesbury, Ontario are presented in this paper. A second paper will deal with the mineralogy and geochemistry of the same deposits.A westerly clay plain at ~50 m and an easterly plain at ~75 m elevation occur in the area. Preconsolidation pressure versus depth curves obtained for clays from both deposits show marked preconsolidation near the top and bottom drainage boundaries and nearly normally consolidated conditions at the centre. This suggests that both sites were loaded by sandy fluvial (deltaic) sediments that were eroded ~70 years after deposition, an ancestral meander of the Ottawa River being responsible for the erosion on the lower clay plain. Two stratigraphic schemes compatible with the σP′ versus depth profiles are presented. For the lower elevation clay plain these schemes suggest erosion of 21 m of deltaic sands, a value generally confirmed by field studies of deltaic sand terraces to the west.The sensitivity of the lower level clays decreases from ~25 at surface to ~5 at depth. The upper level clays are very different, having a maximum sensitivity of ~20 at mid-depth and decreasing towards the top and bottom. These trends reflect differences in the liquidity index for both clays and in salinity for the lower level clays. The low values of sensitivity relate to the relatively high clay mineral content of 51% and salt content of 1–20 g/L measured on these partially "leached" clays.Keywords: Champlain clays, preconsolidation, diffusion, erosion, vane strength, salinity.

ISSN:0008-3674    

DOI:10.1139/t83-032

出版商:NRC Research Press    

年代:1983

数据来源: NRC

摘要:

A theoretically based procedure for predicting and designing for settlement above tunnels constructed in soft ground is outlined. The application of this theoretical technique is discussed and its range of applicability is examined by consideration of four case histories that encompass a wide range of soil conditions and construction techniques. This technique is then used as the basis of a design approach that is described in the paper. It is suggested that this procedure will provide a convenient means of estimating settlement induced by tunnelling in many different soil deposits provided that reasonable construction procedures are adopted.Keywords: tunnels, tunnelling, soft ground, settlement, analysis, design, deformations.

ISSN:0008-3674    

DOI:10.1139/t83-033

出版商:NRC Research Press    

年代:1983

数据来源: NRC