Effect of Initial Fabric on Cyclic and Monotonic Undrained Shear Strength of Gioia Tauro Sand

An experimental study is presented aimed at a direct comparison of the undrained behaviour of a natural coarse sand using speciments reconstituted by different techniques. Undrained monotonic and cyclic triaxial compression tests were carried out on reconstituted specimens of Gioia Tauro sand, as well as on truly undisturbed specimens retrieved by in-situ ground freezing. It is worth noting that Gioia Tauro Plain, on the Calabrian side of the Messina Strait, manifested various types of geotechnical hazards related to soil liquefaction during several catastrophic earthquakes. Two different preparation methods were employed, namely air pluviation and water sedimentation. Soil fabrics resulting from the above methods appear to exhibit different undrained response during monotonic straining. The behaviour of truly undisturbed specimens (and hence with their natural fabric) appears to be similar to that exhibited by water sedimentation reconstituted specimens in both undrained monotonic and cyclic triaxial tests. Finally, in view of assessing equivalent simple shear or in-situ response of the natural deposit, undrained cyclic shear strength characteristics of the tested sand from triaxial tests were compared with those gathered from the simple shear device.