The paper reviews the in situ freezing method to retrieve undisturbed sandy and gravelly soil samples and available laboratory equipments to test coarse grained soils. As for the triaxial equipments, the importance of local strain measurements and other key issues are discussed. It is also shown a case of undisturbed sampling of gravelly soils by in situ freezing in Tuscany (Italy). Comparison of stiffness and material damping ratio of undisturbed and reconstituted specimens is also shown. The main conclusion is that the normalized stiffness and material damping ratio of undisturbed and reconstituted specimens is very similar. It was not possible to compare the liquefaction strength of undisturbed specimens to that of reconstituted ones. In-fact, after completion of tests on undisturbed specimens, the cell pressure of the triaxial equipment failed and there was not enough budgets to repair it. Therefore the data have been compared to those available in the literature. From this comparison, it emerges that the liquefaction strength of undisturbed specimens is much larger than that typically observed for the reconstituted ones. The experimental results of this research also suggest that liquefaction of gravelly soils is possible only in the presence of a given percentage of fine sands and silts. Anyway, this point deserves further researches.
Stress-strain-strength behaviour of undisturbed and reconstituted gravelly soil samples
LO PRESTI, DIEGO CARLO;
2006-01-01
Abstract
The paper reviews the in situ freezing method to retrieve undisturbed sandy and gravelly soil samples and available laboratory equipments to test coarse grained soils. As for the triaxial equipments, the importance of local strain measurements and other key issues are discussed. It is also shown a case of undisturbed sampling of gravelly soils by in situ freezing in Tuscany (Italy). Comparison of stiffness and material damping ratio of undisturbed and reconstituted specimens is also shown. The main conclusion is that the normalized stiffness and material damping ratio of undisturbed and reconstituted specimens is very similar. It was not possible to compare the liquefaction strength of undisturbed specimens to that of reconstituted ones. In-fact, after completion of tests on undisturbed specimens, the cell pressure of the triaxial equipment failed and there was not enough budgets to repair it. Therefore the data have been compared to those available in the literature. From this comparison, it emerges that the liquefaction strength of undisturbed specimens is much larger than that typically observed for the reconstituted ones. The experimental results of this research also suggest that liquefaction of gravelly soils is possible only in the presence of a given percentage of fine sands and silts. Anyway, this point deserves further researches.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
