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

Convention Bandung 2004 (CB2004)
The 33rd 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.