Convention Bandung 2004 (CB2004) The 33^rd Annual Convention & Exhibition 2004

Indonesian Association of Geologist Horizon Hotel, 29-30 Nov, 1 Oct 2004, Bandung

EXPERIMENTAL STUDY ON
LOCALIZATION OF DEFORMATION
(SHEAR ZONE) ON SATURATED
SANDY SOILS IN RING SHEAR TEST

Muhammad Wafid A N

Directorate of Geology and Mining Area Environmcnt

Abstract

Series of tests on saturated sandy soil under undrained and drained shearing conditions, with various relative densities by means of ring shear apparatus were carried out to investigate the shear zone development process The macroscopic structural observations were conducted through “SOBO method” by capturing the oven-dried samples using a camcorder/digital camera. This observation revealed that for dense sand, the shear zone starts to develop at failure and the thickness increases by progress of shear displacement. While for loose sand no obvious developed shear zone at peak shear strength. In the beginning of shear zone formation, the shape of the shear zone was refined concavely with distinct undulating structure (secondary) which gradually changed to become parallel when shear displacement proceed. Further shearing the shape of shear zone was refined convexly with unrecognizable shear surface. Another interesting phenomenon obtained by this study is that when sandy soils has been sheared until reaching the steady state, the coarse and the fine-particles (including the result of grain crushing) within the shear zone became separated by segregation process. At this state, the core part mainly consisted of coarse grain with very limited fine particles, while the fine particles were accumulated at the bottom part of shear zone.