טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentSchwartz Keren
SubjectThe Behaviour of Undisturbed, Saturated Sand during
Undrained Shear
DepartmentDepartment of Civil and Environmental Engineering
Supervisors Professor Mark Lloyd Talesnick
Professor Emeritus Sam Frydman


Abstract

The research focused upon the question of soil fabric and its influence on its mechanical response. It included undrained triaxial tests and has focused on the examination of strength and stiffness of disturbed and undisturbed samples. Disturbed specimens were prepared by one of two different methods: Moist Tamping and Water Pluviation. The validity of two dilation equations was also examined.


The response of the sand to undrained loading was identical in all the tests. The specimens displayed dilative behavior, failed at the same stress ratio and displayed similar stiffness values. Changes in stiffness as shear progressed indicate the even at relatively small axial strain, the soil stiffness decreased drastically to 10% of its initial value. The soil stiffness is strongly affected by changes in the confining pressure as shearing ensues. In particular, the minimal stiffness value was reached at the Phase Transformation point. Both dilation equations that were examined (Rowe, 1962 and Ueng & Chung-Jung, 1990) have been found to be valid, in principle, up to the point of Phase Transformation.


No dependence on loading direction was observed. It has been concluded that the examined sand lacks a unique internal structure. It is suggested that the conditions existing in the site, such as shallow depth and exposure to tides did not allow the development of a unique fabric.


It is suggested to conduct additional investigation into the conditions, which inhibit the development of soil fabric, as well as into the physical nature of Phase Transformation.