A FINITE-ELEMENT STUDY OF THE PRESSUREMETER TEST IN SAND USING A NONLINEAR ELASTIC-PLASTIC MODEL

The stress-strain behaviour of sands is highly nonlinear, even at stre sses well below the peak strength of the sand. The hyperbolic model is a reasonable conceptual model for representing the stress-strain beha viour of sand, but some empirical curve fitting is required to obtain a more realistic model for calculation purposes. This can readily be p erformed for reconstituted samples of sand using laboratory tests. Rec ent evidence shows that the stiffness of natural sands is often much g reater than that of the same sand when reconstituted at the same densi ty and stress state in the laboratory, and it is therefore necessary t o use in situ testing methods to determine the stress-strain behaviour of such sands. In this paper, the finite element method is used to si mulate pressuremeter tests in a soil modelled using a hyperbolic-type model. It concentrates on the behaviour in unload-reload loops, which are often included in pressuremeter tests to measure shear modulus. Th e effect on the whole unload-reload loop of varying some of the model parameters is examined. The results are compared with a high-quality p ressuremeter test in sand. It is concluded that, though the results to date are encouraging, some further experimental work is required to v erify some of the features of the model.