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原文传递 Stability of Embankments on Soft Clay Part 3 of 3:Centrifuge Tests and Numerical Analysis

题名：	Stability of Embankments on Soft Clay Part 3 of 3:Centrifuge Tests and Numerical Analysis
作者：	M.S.S. Almeida and R.H.G. Parry
关键词：	Centrifuge, CRISP, displacements, dissipation, effective stress, embankment, granular columns, normal consolidation, numerical modelling, overccmsolidation, permeability pore pressiare, settlement, shear modulus; soft clay, stability, stage construction, stress history, total stress, undrained shear strength.
摘要：	Centrifuge tests have been conducted to study the behaviour of embankments on soft clay and to provide quantitative data against which to test the predictive power of the Cambridge CRISP program. Soft clay foundations were prepared with an overconsolidated crust over normally consolidated kaolin clay. Methods of conducting site investigation tests on this clay have been described in Parts 1 and 2. Tests were performed both with embankments constructed during flight in stages and in a single lift to failure, with measurements of pore pressures at selected locations, and displacements using a marker grid. Some tests were performed with the clay foundation strengthened using granular columns. An embankment built ina single life, on unstrengthened clay, failed at a height of 11.6m before inducing failure. Heights of 13m were achieved with stage constructed embankments on strengthened foundations, but without any failure occurring. Unexpected large lateral displacements were measured in unstrengthened clay during consolidation periods. Large displacement increases are a good indicator of factor of safety below about 1.3. At corresponding loading the use of strengthened foundations decreased lateral and vertical movements by about 50%. In numerical computation using OUESP, particular attaition was given to the influences of assumed shear modulus and permeability. Prediction of ground level settlements, pore pressure generation and pore pressure dissipatation were good, but horizontal movements and vertical movements of depth tended to be overpredicted. Total stress and effective stress stability analyses were made for embankments on both unstrengthened and strengthened clay foundations. In the latter case allowance was made for the strength of the columns. It was found for the wide spacing of columns, used, the increased pore pressure dissipation due to the presence of the columns had a much greater strengthening effect than any intrinsic strength of the columns themselves. Calculated effective stress factors of safety of failed embankments were found to be 0.9 for unstrengthened and 0.87 for strengthened foundations, the difference between these figures and unity is probably due to a side friction on the box. Total stress analyses significant pore pressure dissipation was occurring during construction.
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