6585844980

Israel

188

ANALYSIS OP TEST RESULTS

The Standard Penetration Test results serve to determine the relative densities of sand deposits and thus the two para-meterB:    the friction angle (0) and the

8tress-strain characteristics of these layers. These parameters are found in-directly by statistical correlations be-tween the SPT test and relative density. For prediction of settlements, use has been madę of local experience from field and laboratory tests, such as vertical and horizontal loading tests, shear tests and actual structure behaviour. The cru-deness of results from SPT values is ta-ken into account in the interpretation of results, as well as the inhomogeneity of sand deposits in naturę, when selec-ting design parameters for application to actual foundation Solutions.

Many years ago, the number of blows (H) was roughly correlated with the density of the sand and thus with the behaviour to be expected from shallow foundations (Terzaghi and Peck, k948, p. 296 and p. 423). This approach was based on a number of piąte loading tests. Since then Holtz and Gibbs (1957) madę tests showing that numerical values could be assigned to the relations between rela-tive density versus Ń - values and showed the effect of overburden pressure as in-fluencing these results. The overburden pressure is a measure of the confining pressure existing at the depth of testing. Coffman (1960) presented these results in graphic form, which has sińce been exten-sively used by engineers. Study of these empirical correlations by Alpan (1970) has resulted in a plot (Fig. No. 5) showing the relation between a guasi-elastic

modulus, E , for sands at different re-s

lative densities and overburden pressures as predicted on the basis of the SPT va-lues.

Special mention should be madę of an ex-tensive study of SPT data for fine sands in Israel, which has been reported by Zolkov (1972). An exaraple of a correla-tion between relative density and friction angle for Israeli dune sands is presented in Fig. 6 (Wiseman, 1962)•

The effect of stress history on the en-gineering properties of dune and beach sands was published by Zolkov and Wiseman (1965). They confirm the influence of stress history on both the standard penetration tests and settlements as indicated by tests run on a site before and after a deep excavation was carried out. The explanation for the higher than

. Fig

. 5 E Yersus SPT for Various Relative Densities and Overburden Pressures s