oa Civil Engineering = Siviele Ingenieurswese - Estimating settlements of footings on sands



In this paper the CBR test is considered as a model plate loading test simulating a prototype footing of which the settlement is desired. CBR values can be determined rapidly by a calibrated portable dynamic CBR-penetrometer (DCP). Scale factors are determined by analysing, with the aid of the elastic theory, a number of case histories in which both settlements and Standard Penetration (SPT) blows were recorded and published by others. Predicted settlements are compared with observed settlements from the cases referred to. The method is shown to be direct and to predict satisfactorily settlements, in the linear range, on sands whether clean, gravelly or slightly clayey, above or below the water table. More realistic extrapolations from other model tests like screwplates and standard plate loadings are made possible. It also appears possible to estimate the dry density from simultaneous penetration and screwplate tests. Furthermore, the modulus of compressibility, though not required to be computed in this direct approach to the prediction of settlements, can be determined from the penetration values and is shown to agree well with field measurements. Finally, design curves are proposed for estimating the allowable bearing pressure on shallow footings.


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