摘要:

The slake durability test has been proposed as a means of predicting the engineering performance of shales. Testing of sections in the two major shale units of Ontario show that the test is capable of making distinctions between apparently similar shale samples. Queenston Shale has generally lower durability than the Georgian Bay Formation samples. Inspection of the shale fabric shows that this is due partly to inefficient cementing by calcite in Queenston Shale, but is primarily because the microcracks in Queenston Shale are more curved than those in Georgian Bay Formation. Variation in shale durability within the shales is controlled by mineralogy. In Queenston Shale, it is controlled almost entirely by calcite cementation. In Georgian Bay, where hard bands (shaly limestone) are present, these dominate the test, giving a high durability. However, pure shale durability is controlled by clay content.Comments on the performance of the test are made that aim to make the testing process and interpretation of the results more reliable. The method appears suitable for shale index testing and should be used as widely as possible in order to establish reliable correlations.

ISSN:0008-3674    

DOI:10.1139/t82-001

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Physical model tests on cemented classified tailings and sand backfills have been carried out to determine the strength requirements for stability when vertical fill faces are exposed. The results of this laboratory scale model testing support a three-dimensional analytical solution developed in the paper, whereby the cement strength requirement can be reduced when rock walls are sufficiently close together to help support the backfill by shearing stresses at the wall–backfill contact.Comparisons with conventional backfill strength design approaches show that substantial reductions in cement usage can be realized by using the three-dimensional design approach, particularly when blast hole stoping can be carried out to heights several times greater than the lateral stoping dimensions.Physical modelling of cemented backfills is discussed in detail in the paper and it is concluded that field scale model testing could be useful in the design stages of the development of mining methods at individual mines.

ISSN:0008-3674    

DOI:10.1139/t82-002

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Weathering or the variation in frequency and tightness of joints may result in an increase in mass modulus with depth for some rocks. This increase in modulus will continue until a depth is reached at which the rock behaves as a sound intact unit and the modulus will be relatively constant with depth below this point. In this paper, elastic solutions are presented for the deformation of such a rock mass due to a uniform or approximately rigid circular loading.Two procedures are described for determining the rock mass modulus profile from plate load test results. The first procedure uses the results from three plate tests to infer the variation in modulus with depth. The second procedure uses the measured variation in displacement with depth below a single plate to infer the mass modulus variation. The application of the two procedures is illustrated by a worked example and by consideration of a field case where the inferred modulus is shown to be in good agreement with alternative modulus variation data.

ISSN:0008-3674    

DOI:10.1139/t82-003

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The proposed method makes use of a conventional total stress analysis, corrected to take into consideration the preconsolidation pressure and the undrained shear strength profiles. Good results are obtained for seven well documented cases of embankment failures, the data of which allow a direct application of the proposed method. Many other failure cases, for which the published data are insufficient to allow such a direct application, are analysed on a statistical basis using a relationship betweencuσp′ andIp. Bjerrum's correction appears as a particular case, only statistically applicable, of the proposed method.

ISSN:0008-3674    

DOI:10.1139/t82-004

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

An investigation of the movement of contaminated groundwater from inactive uranium tailings through a sand aquifer is being conducted at the Nordic Main tailings impoundment near Elliot Lake, Ontario. During 1979 and 1980, multilevel bundle-type piezometers were installed at several locations around the edge of the tailings impoundment. Chemical analysis of water samples from the bundle piezometers indicate that a major contaminant plume extends outward through a sand aquifer from the southeastern part of the Nordic Main impoundment dam.In the vicinity of the contaminant plume, the sand aquifer varies in thickness from about 9 to 15 m. The plume has two distinct segments, referred to as the inner core and the outer zone. The inner core, which has a pH of 4.3–5.0 and extends about 15 m from the foot of the tailings dam, contains several grams per litre of iron and sulfate, and tens of pCi/L of226Ra and210Pb. Water levels in piezometers within the inner core show that groundwater is moving horizontally, away from the tailings impoundment, with a velocity of up to several hundred metres per year. The outer zone, which extends a few hundred metres downgradient from the dam, is characterized by hundreds to thousands of milligrams per litre of iron and sulfate, less than 15 pCi/L of226Ra, and a pH greater than 5.7. Comparison of 1979 and 1980 data shows that the front of the inner core is advancing a few metres per year, which is less than a few percent of the groundwater velocity. This retardation of movement of the inner core is caused by neutralization of the acidic water as a result of dissolution of calcium carbonate in the sand. With the rise in pH, precipitation of iron carbonate and possibly some iron hydroxide occurs and the contaminants of main concern such as226Ra,210Pb, and uranium are removed from solution by adsorption or coprecipitation.

ISSN:0008-3674    

DOI:10.1139/t82-005

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The foundation soil beneath the earthfill section of the proposed Revelstoke dam comprises, in part, a deep silt-clay layer that contains pockets of loose to compact saturated sands. Removal of this material beneath the core of the dam was required for seepage and erosion control. Analyses were performed to determine if considerations of earthquake stability would also require removal of this material beneath the shells.A factor of safety against the occurrence of a liquefaction failure beneath the shells was determined by comparing the dynamic resistance obtained from cyclic triaxial tests on undisturbed samples with the time history of dynamic stresses caused by the design earthquakes. Preliminary analyses clearly indicated that the silt-clay beneath the upstream shell should be removed. Beneath the downstream shell, the computations indicated factors of safety at the lower range of acceptable values and a portion of the silt-clay beneath the downstream shell was removed so that only minor damage would occur even in the unlikely event of liquefaction of the material left in place.

ISSN:0008-3674    

DOI:10.1139/t82-006

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The widely distributed loessic soils of China are described, concentrating on the collapsible soils of the upper strata of the loessic series. A general trend of gradual, steady reduction in the tendency to collapse on wetting is found going in the direction from northwest to southeast. Cases of damage and flooding tests of pits are cited for illustration. Results of electron microscope studies of structural features of loess specimens from different locations are compared with the engineering behavior, especially the susceptibility to self-subsidence and degree of collapsibility.In view of this trend and the differences between loessic soils of different regions, a preliminary zoning of the loessic soils was made, resulting in seven zones as shown on a schematic map.

ISSN:0008-3674    

DOI:10.1139/t82-007

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The validity of using a distribution coefficient (Kd) in the mathematical prediction of strontium and cesium transport through uniform saturated sand was investigated by comparing measured breakthrough curves with curves of simulations using the advection-dispersion and the advection equations. Values forKdwere determined by batch equilibration tests and, indirectly, by fitting the mathematical model to breakthrough data from column experiments. Although the advection-dispersion equation accurately represented the breakthrough curves for two nonreactive solutes (chloride and tritium), neither it nor the advection equation provided close representations of the strontium and cesium curves. The simulated breakthrough curves for strontium and cesium were nearly symmetrical, whereas the data curves were very asymmetrical, with long tails. Column experiments with different pore-water velocities indicated that the shape of the normalized breakthrough curves was not sensitive to velocity. This suggests that the asymmetry of the measured curves was the result of nonlinear partitioning of the cations between the solid and liquid phases, rather than nonequilibrium effects. The results indicate that the distribution coefficient, when used in advection-dispersion models for prediction of the migration of strontium and cesium in field situations, can result in significant error.

ISSN:0008-3674    

DOI:10.1139/t82-008

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Frozen saturated quartz sand containing 20% moisture by weight, when deformed at −30 °C at various strain rates, showed various modes of behaviour such as visco-plastic, almost ideal plastic, and brittle with little plasticity with increasing order of strain rate. The values of peak strength observed for strain rates between 5 × 10−7and 6 × 10−3 s−1were in the range 15–42 MPa, stress being related to strain rate by a power-law equation.

ISSN:0008-3674    

DOI:10.1139/t82-009

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Heaving of floors founded on black shale in the Ottawa region is due to the oxidation of pyrite in it and the subsequent formation of jarosite and gypsum which crystallize between the layers of the thinly laminated fissile shale causing it to expand. Air must gain access to the shale for the oxidation reaction to occur. Work done in Ottawa indicates that air may be prevented from entering the shale by coating the freshly excavated surface with a layer of concrete before construction commences. This has been successful in preventing heave for at least seven years. Additional precautions which are needed to prevent entry of air to the shale after construction of the building are also discussed.

ISSN:0008-3674    

DOI:10.1139/t82-010

出版商:NRC Research Press    

年代:1982

数据来源: NRC