Shear Strength of Gravel and Rockfill Measured in Triaxial and Prismatic Wedge Shear Tests

 

H. Tosun

Assoc. Prof. of Civil Engineering, Osmangazi University, 26480 Eskisehir, Turkey
Email: htosun@ogu.edu.tr

T. Mirata

Professor, Civil Engineering Department,
Middle East Technical University, 06531, Ankara, Turkey
Email: mirata@narwhal.cc.metu.edu.tr

M. Mollamahmutoglu

Assoc. Prof. of Civil Engineering, Gazi University, 06570, Ankara, Turkey
Email: molla@mikasa.mmf.gazi.edu.tr

N.S. Çolakoglu

Project Engineer, 5th Regional Directorate of State Hydraulic Works, Ankara, Turkey

ABSTRACT

The prismatic wedge shear test (priswest) is a relatively new technique for measuring the shear strength of gravels and gravelly clays using a portable frame and a right prismatic box (test mould) consisting of two identical halves separated by 5 mm to 12 mm high spacers which, when removed, leave the plane of shear, measuring 300 mm x 300 mm at the start of shear and inclined at an angle usually between 30o and 45o to the main load P, free for testing. P is applied through two grooved plates with steel balls in between; a relatively small lateral load has a similar effect as the cell pressure in the triaxial test in increasing the average principal stress range in the test. It has previously been demonstrated for 5 mm to10 mm gravel that the priswest gives results consistent with those of drained triaxial tests on 100-mm dia. specimens. A more recent comparison has been made for clayey gravel with particles finer than 38 mm. Presented in this paper are comparisons between the peak strength measured in priswests on several gravels and crushed rock with particles finer than 38 mm and that measured in drained triaxial tests on 191-mm dia. samples. The agreement between the results of the two types of test is remarkable, the minor differences being generally explicable by the fact that the priswest is more nearly a plane strain type of test.

KEYWORDS: gravel, degree of compaction, laboratory equipment, rockfill, shear test, triaxial test, wedge shear test.

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