Journal of Engineering and Applied Sciences.Vol. 3,pp.73-87. 1986 Printed in the USA. All rightsreserved.
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Copyright ©1986 Pergamon Journals Ltd.
EFFECT OF FISSURES ON
SHEAR STRENGTH MEASUREMENT OF SOFT CLAY FROM LABORATORY VANE SHEAR TEST
AYAD A. AL-ZAYDI
Associate Professor Department of Civil Engineering
King Abdulaziz University Jeddah, Saudi Arabia
AHMED M. KHAN
Lecturer
Department of Civil Engineering King Abdulaziz University
Jeddah, Saudi Arabia
Abstract - Natural soil deposits invariably contain fissures, microcracks, slickensides and other discontinuities that influence their shear strength. Little information is available on the effect of fissures on strength measurement from laboratory vane shear test. This investiga- tion is concerned with the effect of such fissures on the shear strength as measured by a laboratory vane shear apparatus. Series of tests were performed on intact and artificially fissured specimens with fissured planes at various orientations. The study revealed that the fissures affect appreciably the shear strength of the soil as measured by the vane apparatus, and it might be suitable to correct the measured strength values before performing bearing capacity or stability analysis.
INTRODUCTION
Vane shear test equipment, in the form of both field and laboratory vanes, has been used extensively as cheap and rapid means of determining the shear strength of cohesive soils [I, 2]. Very little work has been done on the applicability of vane shear test to fissured clays although, quite frequently, natural soils have fissures. These fissures are in the form of slickensides, microcracks and discontinuities. These fis- sures can easily lead to erratic measurements of the true shear strength needed for stability analysis or in the design of foundations as discussed by Alzaydi [3].
In the present investigation, it was intended to explore the effect offissures on the strength measurements from the laboratory vane apparatus. The investigation was carried out to estimate the extent of influence of fissures on the strength measure- ments from the vane test.
Testing was conducted on intact and fissured specimens of an artificially sedi- mented clay. The fissures were prepared artificially according to certain predesigned pattern as presented later.
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