摘要:

The discrepancy between calculated consolidation settlements and measured settlements under a 3.8 m high section of an earth embankment is investigated in this paper. A conventional one-dimensional analysis underestimated the observed settlement by 40%. A two-dimensional finite-element analysis was carried out to assess the effects of lateral spreading on vertical movements, and the results were in close agreement with the measured values.Key words: case history, consolidation, finite element analysis, settlement.

ISSN:0008-3674    

DOI:10.1139/t94-020

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Traditional methods of evaluating evaporation provide an estimate of the maximum or potential rate of evaporation determined on the basis of climatic conditions. Methods such as these are appropriate for open water or fully saturated soil surfaces. Actual rates of evaporation from unsaturated soil surfaces are generally greatly reduced relative to the potential rate of evaporation. A theoretical model for predicting the rate of evaporation from soil surfaces is presented in this paper. The model is based on a system of equations for coupled heat and mass transfer in soil. Darcy's Law and Fick's Law are used to describe the flow of liquid water and water vapour, respectively. Heat flow is evaluated on the basis of conductive and latent heat fluxes. Dalton's Law is used to calculate the rate of soil evaporation to the atmosphere based on the suction at the soil surface. The soil–atmosphere model was used to predict soil evaporation rates, water-content profiles, and temperature profiles for a controlled column evaporation test over a 42 day period. The values computed by the soil–atmosphere model agreed well with the values measured for two columns of Beaver Creek sand in the evaporation test.Key words: modelling, evaporation, unsaturated, soil surfaces.

ISSN:0008-3674    

DOI:10.1139/t94-021

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The deformation characteristics of rockfill materials at very small strains were investigated by comparing the results of monotonic and cyclic loading laboratory tests with geophysical P- and S-wave logging data from the field. Using a precision linear variable differential transformer for displacement, the elastic moduli of rockfill materials at very small strains were measured in monotonic and cyclic loading triaxial tests. The laboratory test results agreed well with the field results. The shear moduli of rockfill materials from both a monotonic loading torsional simple shear test and a cyclic loading torsional simple shear test also showed good correspondence. Furthermore, the shear modulus predicted from the in situ shear wave tests in rockfill dams corresponded reasonably well with the modulus in the large-scale triaxial tests in the laboratory.Key words: deformation characteristics, embankment dams, rockfill materials, laboratory test, in situ test.

ISSN:0008-3674    

DOI:10.1139/t94-022

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A deep-corrugated metal box culvert structure was instrumented with strain gages and tape extensometer reference points in the field. Performance was monitored during backfilling and, paving and under static loads shortly after completion of installation. Beyond the initial study, deflection readings were taken periodically for 3 years. Also, the static load test was conducted during the second and third years to examine changes in structural responses over time. The results of the study showed that the culvert deflection stabilized within the 3 year period. The overall deflection recorded during the construction phases was about 2 cm, and the additional deflection of about 0.8 cm took place during the long-term study period. The deflection, moment, and thrust responses of the culvert under static loads improved over time. This was considered to be because of backfill soil densification under repeated traffic loads.Key words: long-term field performance, culvert, box type, deep corrugation, deflection, live loads.

ISSN:0008-3674    

DOI:10.1139/t94-023

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The paper presents the results of field experiments performed using the Imperial College instrumented displacement pile in a soft, sensitive marine clay at Bothkennar, Scotland. These results are compared with data from similar programmes of experiments performed in other clay types with this pile so that some of the major factors controlling displacement-pile performance may be identified.Key words: displacement pile, instrumentation, sensitive clay, effective stress design.

ISSN:0008-3674    

DOI:10.1139/t94-024

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The theory of dielectrophoresis in clay–water–electrolyte systems is developed in this paper. Dielectrophoresis is the motion of particles generated by a nonuniform electric field. The dielectrophoretic forces on clay particles are determined by the effective polarizability and configuration of the nonuniform electric field. In most clay–water–electrolyte systems, including natural clays, the dielectrophoretic forces are directed towards the lower field intensity, determined by the negative polarizability. In the experimental program, an ac voltage of 60 Hz and 15 kV was applied through insulated electrodes on block samples of Leda clay for 28 days. The relationship between the soil undrained shear strength after treatment and the distribution of electric field provides direct experimental support for the theory developed. Under three electrical-field configurations, the overall shear strengths increased up to 44.0%, concurrent with significant reduction of sensitivity. The improvement of soil properties was also reflected as increases of preconsolidation pressure and shearing resistance in terms of effective stresses. The electrochemical reactions associated with electric current were minimized by insulation to the electrodes.Key words: dielectrophoresis, electrokinetics, soil improvement, sensitive clay, shear strength.

ISSN:0008-3674    

DOI:10.1139/t94-025

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

This paper presents an application of finite-element analysis to deep excavation in layered sandy and clayey soil deposits using a combination of the hyperbolic and the Modified Cam-clay models. In the analysis, the drained behavior of cohesionless soil and the undrained behavior of cohesive soil were simulated using the hyperbolic and Modified Cam-clay models, respectively. A rational procedure for determining soil parameters for each of the models was established. A simulation of the dewatering process during excavation was proposed. The analytical procedure was confirmed through an analysis of three actual excavation cases. Finally, analyses considering pore-water pressure dissipation during the actual elapsed time for each construction phase were carried out. The results indicate that the calculated displacement of a retaining wall during excavation is smaller than that given by undrained analysis. It was thought that some degree of pore-water pressure dissipation actually occurs during the intermediate excavation stages. This results in a decrease in the final deformation of the wall and ground.-surface settlement than would be predicted by undrained analysis.Key words: finite-element analysis, deep excavation, hyperbolic model, Cam-clay model.

ISSN:0008-3674    

DOI:10.1139/t94-026

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The stiffness of soils depends on the state of stress. Therefore, the velocity of wave propagation can be used to assess the state of stress and its changes. Indeed, given sufficient data, measurements can be inverted to produce a tomographic image of the stress field. A preliminary study of this approach was conducted with simulated data and is summarized briefly. Results of an experimental study are then presented. Three common geotechnical systems were tested: a footing, a moving surface load, and a retaining wall. Calculated velocity changes are compared with predicted velocity changes, with stress changes being estimated by classical analytical solutions. Good agreement is found in the three cases. The need for accuracy in travel-time measurements, difficulties in tomographic imaging, and the propagation of uncertainty from inverted velocities to stresses are discussed.Key words: geophysical methods, tomography, wave propagation, stress, retaining wall, footings.

ISSN:0008-3674    

DOI:10.1139/t94-027

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Frost heave in soils is analysed from a fundamental point of view to predict the development of periodic ice lens formation that is observed in frozen soils. A model of simultaneous heat and mass transfer associated with three new concepts is described and was found to exhibit many of the frost heave features observed in laboratory tests. An efficient frost heave parameter termed the segregation potential, SP, is also described and found to be an adequate input to a general formulation of heat and mass transfer for the prediction of frost heave in soils for both laboratory and field conditions. Representative values of SP depend on the stress and thermal histories of the soil deposit. The SP-based approach can be used for solving two-dimensional frost heave problems and yields stress, temperature, and ice-content distributions with time.Key words: frost heave, soils, segregation potential, simulation, thermodynamics.

ISSN:0008-3674    

DOI:10.1139/t94-028

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

High-strain dynamic pile tests using the pile driving analyzer (PDA) and the Case method have been available in Canada for over 15 years. During that period of time, the hardware has evolved considerably but the way the data is interpreted has basically remained the same. The evaluation of the bearing capacity of the tested pile still uses the Case method, with the Case J factor being calculated either from the results of a static load test or, more often, from the results of one or moreCAPWAP(Case pile wave analysis program) analyses. A computer program has been developed to estimate the bearing capacity of piles using the dynamic test results produced by the PDA. This program uses direct correlations between PDA data andCAPWAPresults. It also includes an artificial intelligence module trained to predictCAPWAPpile capacity. It is not designed to replace theCAPWAPprogram, but rather to indicate when an additionalCAPWAPanalysis might be required.Key words: dynamic load test, computer program, artificial intelligence,CAPWAP, Case method.

ISSN:0008-3674    

DOI:10.1139/t94-029

出版商:NRC Research Press    

年代:1994

数据来源: NRC