EXPERIMENTAL EVIDENCE INTO THE IMPACT OF SAMPLE RECONSTITUTION ON THE PORE WATER PRESSURE GENERATION OF OVERCONSOLIDATED SILTY SAND SOILS

Abstract

The objective of this laboratory investigation is to study the effect of the sample reconstitution on the excess pore water pressure (∆u) of medium dense (D_r = 52%) normally consolidated and overconsolidated sand-silt mixtures under monotonic loading conditions. For this purpose, a series of undrained monotonic triaxial tests were carried out on reconstituted saturated silty sand samples with fines content ranging from 0% to 40%. The confining pressure was kept constant to 100 kPa. The samples were prepared using two depositional methods named: dry pluviation and wet deposition for different overconsolidation ratios (OCR = 1, 2, 4, and 8). The test results show that normally consolidated and overconsolidated wet deposition samples exhibit higher excess pore water pressure in comparison to normally consolidated and overconsolidated dry funnel pluviation samples. The obtained soil trend can be attributed to the effect of water during the preparation of the wet deposited samples cane which is at the origin of initiating higher void ratios and consequently, making the structure of the soil more compressible during the shear process. In the other hand, the normally consolidated and overconsolidated dry pluviation samples showed an excess pore water pressure increase with the increase of fines content and the inverse trend was observed in the case of normally consolidated and overconsolidated wet deposited samples. This is due to the nature of the low plastic fines in making the soil structure more or less compressible and consequently increase or decrease the excess pore water pressure of dry funnel pluviated and wet deposited samples respectively. The obtained data confirm the existence of a reliable relationship between the excess pore water pressure of overconsolidated and normally consolidated sand-silt mixtures for both sample preparation techniques under consideration (dry funnel pluviation ＂DFP＂ and wet deposition ＂WD＂).