摘要:

Twenty topples are described from Rock Glacier Site, 2 km north of the summit of the Highwood Pass in the Front Ranges of the Rocky Mountains in Alberta. In situ field testing and laboratory tests indicated that the external force driving the toppling process is frost action within a weathered shale zone. A stability analysis of the slope included examining rock falls, rupture surface formation, and slides. Rock falls were the dominant mode of landsliding. Surfaces of rupture develop when the amount of angular rotation of the toppling rock mass is over 16°. Slides along continuous surfaces of rupture are possible in rock masses with no cohesion and reduced friction angles. Topples cause rock falls, which lead to shallow slides in the rock-fall colluvium.Key words:topple, rupture surface, rock fall, rock slide, Rocky Mountains, slope stability.

ISSN:0008-3674    

DOI:10.1139/t96-095-316

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

When on-site soil is not granular, substantial cost savings can be achieved if a stable, steeply sloped, reinforced retaining system, backfilled with on-site fill can be sustituted for a vertical retaining wall with granular fill. Centrifuge modeling was used in this work to investigate the failure and prefailure behaviour of 14 reduced-scale geotextile-reinforced steep model slopes of 45, 63.4, 71.6°, backfilled with cohesive soil and constructed on either firm or rigid foundations. The overall performance of model slopes on firm foundations was found to be better than that of similar models on rigid foundations. A stability analysis, using the Bishop simplified method incorporating reinforcement, was found to be a good predictor of the behaviour of models.Key words:reinforced soil, centrifuge modeling, geotextile, retaining structure, slope stability.

ISSN:0008-3674    

DOI:10.1139/t96-096-317

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

A laboratory research program was conducted to evaluate the long-term hydraulic performance of sand–bentonite liners augmented with organophilic clay and permeated with diesel fuel. This program was also designed to establish guidelines for the incorporation of organophilic clay in sand–bentonite liners. The study involved three areas of testing. The first was to characterize the materials. The second was to evaluate various combinations of materials and preparation techniques through hydraulic conductivity tests. The third area involved unconfined infiltration tests. The primary hydraulic conductivity testing was broken into three phases. These investigated the hydraulic conductivity of organophilic sand–bentonite liners using various percentages of organophilic clay and evaluated the hydraulic performance of these specimens when permeated with distilled water and diesel fuel. Hydraulic conductivity was measured in specially designed low gradient, low effective stress stainless-steel triaxial permeameters. The results of this test program indicated that small percentages (3%) of organophilic clay in a sand–bentonite liner material could effectively be used to avoid desiccation cracking in a liner permeated with petroleum products. High percentages (7.5%) of organophilic clay in a sand–bentonite mixture resulted in a liner permeable to water, but reduced permeability to diesel fuel.Key words:organophilic clay, diesel fuel, bentonite, liners, hydraulic conductivity, triaxial permeability tes

ISSN:0008-3674    

DOI:10.1139/t96-097-318

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Recognition and detailed mapping of glacigenic fractures and reactivated joints, along with such glacigenic features as striae and till fabrics, prove critical in predicting ground control hazards such as pit wall failure. Following a period of heavy rain in the autumn of 1991, a failure occured on part of the wall of an open-pit mining operation on the Heath Steel Mines property. The failure surfaces bounding the complex landslips of the pit wall were all either original glacigenic fractures or other joints reactivated during Late Wisconsinan glacier overriding. Apart from differential movement, such features include joints filled with coarse sand or clay. Comparaison of the geometry of glacigenic fractures in failed areas with the same features in areas just as densely fractured, but which did not fail, reveal a combination of circumstances where failure was predictable. In this case failure of an unstable rock mass resulted from unfavourable kinematic relationships involving the following: the low strength of clay- and sand-filled joints, the presence of highly permeable and weathered joint conduits, the unfavourable geometry between wall and joint orientation, and an occurrence of increased fluid pressure along the joints from high rainfall that triggered movement.Key words:glacitectonics, geotechnical, wall failure, excavations, rock-quality data, instability.

ISSN:0008-3674    

DOI:10.1139/t96-098-319

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The construction of the cut-and-cover tunnels and depressed roadways of the Central Expressway (CTE) Phase II, Singapore, involved deep excavations. An extensive instrumentation program was carried out to monitor the behaviour of the excavations. The performance of three instrumented excavations from the construction of the CTE Phase II have been documented and analyzed using the finite element method (EXCAV) or finite difference method (FLAC). The results of the analyses show that the computed wall movements agree well with field measurements of wall movement and the computed wall bending moments generally agree quite well with those obtained from back-calculation.Key words:deep excavation, stiff clay, numerical analysis, displacements.

ISSN:0008-3674    

DOI:10.1139/t96-099-320

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Results of centrifuge modelling of socketed caissons in a weak model rock made of cement, sand, bentonite, and water are presented. The model socketed caissons were made from aluminium tubing with a structural stiffness closely identical to a solid concrete pile. In the first series of tests, model sockets were tested in axial compression to determine the effect of socket roughness on side resistance. In the second series, model sockets were subjected to lateral loading. The experimental results are compared with existing design methods used to predict ultimate capacity and load deformation response. Data obtained from other model studies and full-scale tests are also presented and compared with the centrifuge modelling data.Key words:socketed caissons, centrifuge modelling, weak rock, lateral deformation, axial deformation.

ISSN:0008-3674    

DOI:10.1139/t96-100-321

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The full-scale hydraulic performance of a soil–bentonite liner depends on the homogeneity of bentonite content in the mix; any prediction must consider the distribution function of the local bentonite content, mainly that of below average values. The degree of homogeneity in the field depends on the mixing method and the sand characteristics. Several techniques, such as double hydrometer tests, or methylene blue tests, can evaluate the bentonite content in a sample. They are not reliable when the sand varies in gradation and mineralogy. This led to the investigation of whether X-ray diffraction could determine the bentonite content in a soil–bentonite sample and a method was developed. First, the mix must be thermally treated to eliminate the variation in diffraction intensities resulting from the variable hydration of the montmorillonite. Then, an internal standard must be used to control the X-ray absorption. This paper presents the preliminary calibration work, the different steps to follow for quantitative determination of the bentonite content, its accuracy, and its application to a special project where the usual methods were not reliable due to a large variability in sand properties. The parameters needed to calculate the bentonite content in a mix depend on the type of bentonite but not on the type of sand. The accuracy depends on the variability in mineralogical quality of the bentonite powder. For one project, it is shown that the in situ mixing technique produced highly variable local bentonite contents, and that the average content was higher in the lower half of the lift than in its upper half.Key words:liner, bentonite, control, permeabilit

ISSN:0008-3674    

DOI:10.1139/t96-101-322

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Wave propagation is a constant-fabric macrophenomenon, suitable to microinterpretation. Both velocity and attenuation characterize state, including inherent and stress-induced anisotropy. The purpose of this research is to study the effect of isotropic and deviatoric stresses on wave propagation in particulate materials at low strains and to interpret results at the microlevel. A resonant-column device was midified to allow for the application of axial extension and axial compression deviatoric loading. The fixed-free boundary condition of the sample was maintained. Data for round, hard-grained sand show that shear wave velocity and attenuation are primarily dependent on the mean stress on the polarization plane, with minimal effect of the deviatoric component, in agreement with prior observations at stress ratios less than 2–3. Attenuation is strongly correlated with the mean stress in the polarization plane and the level of shear strain. Damping does not vanish at low strains, contrary to predictions based on hysteretic behaviour; hence, other loss mechanisms must take place at low strains. Low-strain wave parameters are adequately corrected for mid-strain using modified hyperbolic models. Measured velocity and damping trends during isotropic and anisotropic loading qualitatively agree with predictions based on regular arrays.Key words:mechanical waves, resonant column, damping, shear modulus, stress anisotropy, random vibration

ISSN:0008-3674    

DOI:10.1139/t96-102-323

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

A major concern in the design of landfill covers and liners that use compacted clays as the hydraulic barrier is freezing and thawing. Paper mill sludges have been used in landfill covers to subtitute for clays as the hydraulic barrier. In this study, laboratory-compacted paper sludges have been subjected to one-dimensional and three-dimensional laboratory freezing and thawing cycles. Freezing and thawing increased the hydraulic conductivity of the paper sludges about one to two orders of magnitude. To determine why freezing and thawing cause an increase in hydraulic conductivity, an evaluation of the effects of freezing and thawing on the macrostucture of paper sludges was conducted. Frozen thin sections of paper sludges were prepared after freeze–thaw cycling and were compared to frozen thin sections of a compacted clay. Macrostructure analysis of the paper sludge and clay thin sections was conducted by using back lighting to reveal the details of ice structure. Analysis of the clay thin sections revealed ice lenses and shrinkage cracks. Ice lenses and shrinkage cracks in sludge thin sections were difficult to determine when the same procedure for compacted clays was used.Key words:freeze, paper sludge, landfill, permeability, macrostructure, thin sections

ISSN:0008-3674    

DOI:10.1139/t96-103

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The Bureau de normalisation du Québec and the Canadian Standards Association developed standards for the determination of the liquid limit using the fall cone method and the percussion method. This technical note compares the liquid limit values obtained with these two methods and also compares them with those obtained using methods and standards developed in other countries.Key words:clays, liquid limits, fall cone, standards

ISSN:0008-3674    

DOI:10.1139/t96-104-324

出版商:NRC Research Press    

年代:1996

数据来源: NRC