摘要:

Mining with backfill has been the subject of several international meetings in recent years and a considerable research effort is being applied to improve both mining economics and ore recovery by using backfill for ground support. Classified mill tailings sands are the most commonly used backfill material but these fine sands must be stabilized before full ore pillar recovery can be achieved. Normal portland cement is generally used for stabilization but the high cost of cement prohibits high cement usage. This paper considers the use of reinforcements in cemented fill to reduce the cement usage. It is concluded that strong cemented layers at typical spacings of about 3 m in a low cement content bulk fill can reinforce the fill and reduce the overall cement usage. Fibre reinforcements introduced into strong layers or into bulk fills are also known to be effective in reducing cement usage. Some development work is needed to produce the ideal type of anchored fibre in order to realize economic gains from fibre-reinforced fills.Key words: mining, backfilling, ground support, soil–cement, fibre reinforcement.

ISSN:0008-3674    

DOI:10.1139/t87-024

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The behaviour of a single vertical pile embedded in saturated sand and subjected to cyclic static and dynamic loading is studied using an extensive centrifuge model testing program. A reliable data reduction method allows computation of the dynamic and static cyclic lateral pile resistance–deflectionp–ycurves. The results are compared with full-scale dynamic test results and oil industry design guidelines.From these comparisons, the centrifuge technique appears to model the dynamic soil–pile system properly. For loadings causing significant nonlinearity, the static stiffness appears to be greater than the dynamic stiffness, while material hysteresis appears about the same in each case. Current American Petroleum Institute guidelines for static cyclic loading appear to overestimate the dynamic lateral resistance for medium dense sands.Key words: centrifuge model, cyclic loads, dynamic response, lateral loads, liquefaction, model tests, pile lateral loads.

ISSN:0008-3674    

DOI:10.1139/t87-025

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Slow, recurring downslope movements in northern climates are frequently referred to as "creep movements," and are usually related to outwards freezing followed by vertical thawing movements. An alternative mechanism is examined in the reported test data.Undisturbed block samples of proglacial clay from a slope near yellowknife, N.W.T., have been tested by cyclically varying the pore-water pressure in triaxial specimens by an amount Δu, and measuring the resulting strains per cycle. The specimens were initially anisotropically consolidated with normal and shear stresses corresponding to those in the moving mantle. Drainage was permitted throughout the testing. This procedure represents changes that can occur in a natural slope from (a) seasonal groundwater level changes and (b) elevated pore-water pressures that accompany thawing. After 60–100 cycles, the pore-water pressure was systematically increased to the value Δufat which the samples failed. This occurred on a steep, low-stress envelope, approximatelyc′ = 4 KPa,. The envelope is probably controlled by the nuggety macrostructure of the clay and appears to be slightly to the left of thelocus.The strains per cycle were approximately linear in the range 30–100 cycles. As a first approximation they have been modelled as varying linearly with the ratio Δu/Δufalmost up to failure at Δu/Δuf = 1.0.Key words: downslope creep, solifluction, slope stability, clay, pore-water pressure, cyclic loading, low-stress failure.

ISSN:0008-3674    

DOI:10.1139/t87-026

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

A review of several available stability chart solutions for simple earth slopes was undertaken to assess their suitability for use with partial safety factors. Thecharts and Casagrande resistance envelopes were found to be particularly suited to the use of such factors and for comparing this approach with the traditional practice of using total safety factors. Casagrande resistance envelopes and factor of safety charts are presented for a range in slope inclinations.Key words: earth slopes, stability charts, total safety factors, partial safety factors, Casagrande resistance envelopes.

ISSN:0008-3674    

DOI:10.1139/t87-027

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The construction of the Domed Stadium in Toronto necessitated the relocation of the John Street Pumping Station and associated water supply tunnels for the downtown Toronto area. The proposed structures include tunnels, shafts, and a new pumping station built in or founded on rock. The shale rock of the Georgian Bay formation is known to possess high horizontal stresses and time-dependent deformation and at this site contains numerous horizontal fractures filled with clay seams. This paper presents the results of the site investigation, field and laboratory testing, analysis, and design for the buried structures. Special provisions for "rock squeeze" for different structures are also described.Key words: tunnels, shafts, shale, squeezing rock, horizontal stress, rock–structure–time interaction.

ISSN:0008-3674    

DOI:10.1139/t87-028

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

This paper presents a series of experimental measurements of the bearing capacity of spread foundations resting on a layer of sand of finite thickness; they are carried out using circular or rectangular laboratory models. After an analysis of the graphical expression of results illustrating the foundation–soil behaviour under the applied load, we study the relationships between the bearing capacity coefficient and the different parameters of the problem: relative thickness of the compressible layer, interfacial foundation–soil and soil–substratum conditions of friction, shape factor of the models.In every case, the results have been compared with available results of other authors and related with existing theoretical or semiempirical methods; these comparisons lead to the proposal of a rational testing procedure for determining the ultimate load for shallow foundations.Key words: foundations, bearing capacity, interfaces, scale effect, shape factor, bilayer.

ISSN:0008-3674    

DOI:10.1139/t87-029

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

In 1982, the Government of Alberta began a program to rehabilitate and expand existing irrigation headworks systems within southern Alberta. Particular emphasis was placed on effectively minimizing future seepage from these canal systems. To fulfill this requirement, Alberta Environment undertook an extensive study of methods of seepage control that would be most appropriate for use in this program. The study concluded that the installation of a complete canal buried membrane lining was one of the most effective methods for controlling seepage. The geomembrane material selected for use as the buried liner for this installation was 0.5 mm (20 mil) thick polyvinyl chloride (PVC). This paper presents the basis on which the complete canal buried membrane lining system was selected, the reasons for selecting the 0.5 mm (20 mil) thick PVC as the lining material, the quality control program for monitoring the purchasing of the PVC material, and the installation procedures used for placing the membrane within the canal cross section. The design criteria and construction procedures relevant to the earth cover material being placed on the membrane liner are also presented.Key words: irrigation, canals, seepage, lining, geomembrane, performance.

ISSN:0008-3674    

DOI:10.1139/t87-030

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Thermally induced water migration beneath chilled structures in frozen ground near its melting point has been considered by some as a possible source of heave and structural distress. This paper analyses the two-dimensional problem of thermally induced water flow in frozen soils beneath a chilled buried pipe, both for steady state and early transient conditions. The analysis has identified the primary variables of interest in the problem of thermally induced heave in frozen ground, and by omitting some second-order effects has obtained a relatively straightforward relationship for the steady state heave rate due to this process. Using published relationships for hydraulic conductivity of frozen soils, it is concluded that heave induced by this mechanism will be relatively minor, and should not result in significant pipe bending or structural distress in the long term. Initial transient and seasonal effects were studied using the same govering equation for fluid flow, coupled with the author's two-dimensional thermal simulator. Additional heave due to these effects does not appear to increase the overall predicted heave greatly.Key words: heave, water flow in frozen soil, pipeline, frozen soil, permeability.

ISSN:0008-3674    

DOI:10.1139/t87-031

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

This paper considers shoring of excavations associated with construction of buildings with particular reference to the selection of the earth pressure coefficient. The empirical criteria, given by R. B. Peck and other participants at the International Conference on Soil Mechanics and Foundation Engineering in Mexico City in 1969, are examined. Several case histories of deep excavations are given where acceptable deformations were experienced using active earth pressure coefficients in shoring design. Where failure occurred, it was attributed to causes unrelated to the selection of earth pressure coefficient.Key words: shoring, earth pressure coefficient, deformations.

ISSN:0008-3674    

DOI:10.1139/t87-032

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Triaxial testing has examined the influence of storage time and reconsolidation procedures on normally consolidated and overconsolidated samples of reconstituted clay prepared with high pore-water pressures to simulate underwater deposits. "Samples" of illite were consolidated one dimensionally, off-loaded without drainage, stored undrained, reconsolidated, and sheared undrained. The storage times were 15 min, 1 day, and 7 days. Reconsolidation pressures were (1) isotropic to, (2) isotropic to, and (3) anisotropic to,. The results were compared with "specimens" that had not been off-loaded.Different undrained storage times had no effect on the strengths after reconsolidation, but the strengths were affected by the reconsolidation pressures. Anisotropic reconsolidation produced the best agreement between the control specimens and samples in terms of their strengths andAf-values. The duration of storage time did affect stress–strain parameters such as the undrained compression modulusE50and the pore-water pressure parameterAf.Key words: underwater, offshore, clay, illite, sampling disturbance, triaxial, storage, reconsolidation, undrained, strength, stiffness.

ISSN:0008-3674    

DOI:10.1139/t87-033

出版商:NRC Research Press    

年代:1987

数据来源: NRC