The behaviour of shallow foundations on structured soils



This paper reports on a numerical investigation into the behaviour of a shallow foundation resting on a uniform deposit of a natural calcarenite. Analyses were performed using the Imperial College Finite Element Program in which the soil was reproduced by means of a modified version of the constitutive model proposed by Lagioia and Nova [1995] for structured soils. The shape of the load-displacement curve, as derived from the numerical results, is similar to that observed from loading tests performed on hoth full scale foundations and from plate loading tests on similar cemented soils. The numerical results show that the sharp kink in the load-displacement curve, which produces the typical bi-linear shape observed in practice, is not associated with the onset ofplastic deformations in the soil. Rather, this kink marks the stage at which there is degradation ofintenparticle bonds in the soil underneath the foundation. Bond degradation first occurs under the edge of the foundation and initially progresses downward forming a vertical bandl Subsequently it spreads laterally underneath the foundation. The relation between load and vertical displacement is linear until the degradation extends under the foundation. A typical punching type mechanism develops with compression ofthe soil mass underneath the foundation, the soil adjacent to the foundation remaining undisturbed and cemented. An ultimate collapse load is not attained as the load carried by the foundation keeps increasing with settlement.

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AUTORI: Lagioia R., Potts D.M.
Numero di pagine: 52

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