摘要:

In connection with the design of offshore structures and bridge foundations, the ultimate bearing capacity of rigid piles and pile groups in clay has been determined under various combinations of eccentricity and inclination of the load varying from the vertical to horizontal directions. The results of load tests on single rigid model piles and freestanding groups are compared with theoretical estimates. The influence of eccentricity and inclination of the load on the ultimate bearing capacity can be represented by simple interaction relationships between the ultimate loads and moments and between the axial and normal components of the ultimate load. The effect of a pile cap resting on the soil in piled foundations and the influence of pile flexibility on the ultimate load are examined briefly.Key words: bearing capacity, clay, eccentric load, inclined load, pile groups, pile–soil interaction, rigid piles, ultimate load, ultimate moment.

ISSN:0008-3674    

DOI:10.1139/t84-043

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The failure envelopes of many soils are significantly nonlinear and the effect of this curvature on slope stability is examined. Charts, based on circular arc stability analyses, have been prepared and make possible the rapid assessment of the stability of slopes of simple geometry in uniform soils with curved failure envelopes. The effect on the factor of safety against stability failure of (i) the degree of curvature of the failure envelope of the soil, (ii) the magnitude of the pore pressure ratio within the slope, and (iii) the depth to a hard stratum has been investigated.Key words: depth factor, pore pressure, safety factor, shear strength, slope, stability.

ISSN:0008-3674    

DOI:10.1139/t84-044

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A study was carried out on the structural response of a reinforced earth retaining wall model subjected to the action of a surcharge strip load aligned parallel to the wall head. Effects of both vertical and horizontal load components were investigated. Horizontal loads were applied in two directions, namely, towards the wall face and away from the wall face. The stress distribution pattern in the reinforcing elements and the change in stress distribution occurring in the reinforced earth medium were also studied. Results were generated for various loading conditions, including variations in the load distance from the wall face. Contour diagrams showing the ratio of reinforcing element stress to applied horizontal load intensity, as well as contour diagrams showing the ratio of horizontal soil stress to applied horizontal load intensity, were constructed. Experimental results were compared with the theoretical stress distribution that exists in a semi-infinite elastic medium, and also with design procedure currently in use for reinforced earth retaining walls under horizontal surcharge strip loading. Significant differences were found between the results based on the design method now in use and those obtained from the model study.Key words: reinforced earth, vertical and horizontal strip load, reinforcing elements, stress distribution, stress-sensitive regions, contours, deflections.

ISSN:0008-3674    

DOI:10.1139/t84-045

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A model is proposed describing continuous flow between saturated and unsaturated soil. The flow is assumed to be two dimensional and under steady state conditions. In the unsaturated zone, the coefficient of permeability is treated as a function of pore-water pressure head. The nonlinear differential equation governing the flow is solved using an iterative finite element scheme. The flow equation for an element is derived using the Galerkin weighed residuals method. Several example problems are solved and compared with flow net solutions. The proposed flow model is superior to traditional models, which consider flow only in the saturated zone. The results show that the zero pressure isobar is not an upper flow boundary. The finite element solution is shown to be relatively insensitive to the function used to express the relationship between the coefficient of permeability and the pore-water pressure head.Key words: saturated–unsaturated, pore-water pressure, head, phreatic line.

ISSN:0008-3674    

DOI:10.1139/t84-046

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

A theory for the design of laterally loaded piles in permafrost is presented. The approach is valid for icy soils or ice, where secondary creep displacements will be responsible for the majority of the soil strain under sustained load. Initially, the paper studies in some detail the response of a short, rigid pile embedded in a nonlinear viscous medium. The concept of a flexible elastic pile in a viscous continuum is then introduced, and a relatively straightforward numerical procedure must be introduced to obtain a solution. Once the limiting or design ground surface displacement rate is established by the designer, the paper shows how a typical chart relating lateral pile load to average ground temperature can be prepared.The available (but limited) data base is reviewed for field pile load tests carried out in the early 1970's in Inuvik, N.W.T. and some laboratory model pile tests carried out in connection with this study. Using available long-term secondary creep data for ice and icy silts, predictions for the lateral creep response of piles can be carried out. Agreement between prediction and observation is certainly encouraging and points the way to further research and field testing in this area. Finally, the paper briefly discusses the resistance of rigid fixed-headed piles to lateral loads, and the resistance of a pile in permafrost to the application of a pure moment.Key words: lateral piles, permafrost, creep, model, field tests.

ISSN:0008-3674    

DOI:10.1139/t84-047

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Gassy soils are defined as those soils which contain a relatively large amount of gas dissolved in the pore fluid. Examples include the Alberta Oil Sands, marine sediments from deep ocean locations, geopressure reservoirs along the Gulf Coast, and other naturally occurring, gas-charged reservoirs.The equilibrium behaviour during unloading with undrained boundary conditions is examined. Contrary to conventional experience with soils containing only a small amount of gas, gassy soils exhibit an equilibrium pore pressure response close to zero. Effective stress, and hence strength, decrease commensurately with total stress at the soil boundary.Laboratory observations of gassy soil behaviour are presented, which confirm the predictive accuracy of the theoretical model. Parameters important to the determination of gassy soil behaviour include thein situstate of stress (σ0andu0), the liquid/gas saturation pressure (ul/g), the gas solubility (H), saturation (S), and the soil and liquid compressibilities (βTand βL).Key words: undrained, pore pressure, compressibility, gas, shear strength, unloading, laboratory, ex-solution.

ISSN:0008-3674    

DOI:10.1139/t84-048

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Impact resistance, the deceleration-time response of a moving body upon impact with a surface, can be used to measure the hardness of a soil surface. A simple method for measuring impact resistance is presented. Impact resistance of three soils (Preston sand, Haldimand clay, and Guelph loam) was measured over a range of moisture and subzero temperature conditions. Impact resistance of frozen soil was found to increase with increasing moisture content, decreasing temperature, and increasing particle diameter. Temperature effects on impact resistance were minimal below −4 °C. Under field conditions, increased impact resistance due to increased particle diameter may be compensated for by reduced moisture content.Key words: density, dynamic loading, grain size, soil strength, sports fields.

ISSN:0008-3674    

DOI:10.1139/t84-049

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

Permanent way support systems (roads, airfields, railways) subject to moving load, soil deposits subject to earthquakes, and soil beneath offshore structures subject to wave loading are classical examples of field situations where the soils will experience varying degrees of principal stress rotation. To assess the effects of this principal stress rotation, comparisons were made between the responses of a dry sand when subjected to stress-controlled repetitive triaxial and repetitive simple shear testing. Based on findings from this test program, an attempt was made to analyse the deformation response of a model footing simulating the railway field situation.Principal stress rotation was shown to be a major factor influencing the behaviour of dry granular material when subjected to repetitive load, the effect of which was to induce permanent deformation while the elastic response remained unchanged. The applicability of repetitive triaxial and repetitive simple shear testing in these circumstances is shown to be complex, and rational design methods for field situations involving repetitive loads have been reevaluated.Key words: principal stress rotation, repetitive load, repeated load, cyclic load, granular, triaxial test, simple shear test.

ISSN:0008-3674    

DOI:10.1139/t84-050

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The geochemical mass transfer model WATEGM-SE is used to illustrate by example potential chemical reactions that can occur at a hypothetical low-temperature thermal energy aquifer storage facility. Important processes that control the chemistry include heating and cooling of the water, equilibration of the pumped water with the atmospheric partial pressure of CO2and O2, and the mixing of the injection water with the native groundwater during the injection, storage, and recovery cycles. For the given example, 0.3 mmol/L of calcite would be precipitated under closed system pumping and heating from 10 to 50 °C while a total of 1.9 mmol/L would be precipitated under the open condition. If this calcite were to form scale within the facility's piping then considerable lengths can be affected depending on the pumping rate. Alternatively, if the precipitate is kept in suspension it will be transported to the injection well and will be filtered out by the aquifer itself. This filtration can result in significant decreases in porosity and hence permeability in the immediate vicinity of the injection well. Mixing of the injection water with the native groundwater changes the water chemistry and can result in mineral supersaturation or undersaturation depending on the composition of these waters and the proportions in which they are mixed. The effect of mixing on the given example is undersaturation with respect to calcite and supersaturation with respect to amorphous Fe(OH)3. The pe values in the simulations of mixtures of an oxidizing injection water and a reducing native groundwater yielded some results with significantly higher pe values than the oxidizing injection water. The use of equilibrium geochemical mass transfer models tempered by an understanding of their limitations may prove to be an effective tool for evaluation of potential chemical reactions associated with low-temperature aquifer thermal energy storage facilities.Key words: thermal energy storage, geochemical equilibria, groundwater, simulation, scale formation, mixing.

ISSN:0008-3674    

DOI:10.1139/t84-051

出版商:NRC Research Press    

年代:1984

数据来源: NRC

摘要:

The results of laboratory andin situtesting and test blasting, the observations made on a test embankment, and a description of actual construction practice associated with engineering studies for the management of uranium mill tailings at Elliot Lake, Ontario are presented. Relative density values inferred from standard penetration tests and cone penetrometer tests are shown to be inconsistent with relative density values determined from maximum and minimum void ratios. Some of the data contradicts existing correlations.The compressibility ofin situsaturated tailings is presented in graphical form in terms of void ratio, vertical effective stress, and mean grain size. Hydraulic conductivity is shown to range over many orders of magnitude, depending on the void ratio. The observations on an instrumented test embankment are used to explain the appropriate selection of geotechnical parameters that gave good agreement between back-calculated and observed settlements. One-dimensional consolidation theory was found to be valid for the embankment case. It is necessary to account for changes in soil properties that occur during the consolidation process in order to obtain a good fit between back-calculated and observed settlements. The successful use of tailings sand for embankment construction is described. On the basis of normalized standard penetration resistance values, it is concluded that localized zones of saturated tailings may be prone to liquefaction under predicted earthquake loadings.Key words: uranium tailings, geotechnical parameters, relative density, test embankment, liquefaction.

ISSN:0008-3674    

DOI:10.1139/t84-052

出版商:NRC Research Press    

年代:1984

数据来源: NRC