بررسي تغييرات تنش اصلي مياني در حالت كرنش صفحه اي براي مصالح دانه اي

Investigation of Intermediate Principal Stress Variations in Granular Materials

The present research describes the variations of the intermediate principal stress, O2 , in plane strain condition which occurs in many earth structures, such as embankment dams, retaining walls and strip footings. For this purpose a series of drained monotonic plane strain tests on Leighton Buzzard sand under different initial magnitudes of a2 were performed. The sand samples were initially packed to dense and loose samples. The Biaxial Tester, which is able to simulate the plane strain condition and also to measure the variation of O2 during the test, was employed in the research. It is shown that the stress-strain response of sand and its shear strength at failure do not vary significantly and almost independent of the initial magnitudes of o2, but are dependent on its initial void ratio. This implies that if different initial values of o create various directional anisotropic structures, they play no part in the plane strain tests. Also a numerical model, which is capable of including o•, is proposed to predict particularly stress strain response of sand and magnitude of a2 at failure. The variations of stress ratio Qyʹ(o, +-6r) were monitored during shearing to clarify the significance of intermediate principal stress.