Applications of the Cylindrical Wedge Shear Test to the Study of Shear Strength of Undisturbed and Compacted Soils T. Mirata Professor, Civil Engineering Department, Middle East Technical University, 06531, Ankara, Turkey Email: mirata@narwhal.cc.metu.edu.tr M. Varan Formerly research student in Civil Engineering, Middle East Technical University, Ankara A. Seçkin Formerly research student in Civil Engineering, Middle East Technical University, Ankara K.F. Gün Formerly research student in Civil Engineering, Middle East Technical University, Ankara
			ABSTRACT

The cylindrical wedge shear test (cylwest) entails the shearing of a cylindrical soil sample enclosed in a thin-walled sampling tube, cut along a plane between 30 and 45 degrees to its axis, and held temporarily together by suitable spacers and screws during sample placement; the upper half is clamped in the cross-beam of a portable frame or available compression machine; the confining screws and spacers are removed, and the soil sheared by increasing the axial load applied through two grooved plates with steel balls in between. The shear strength envelope obtained by cylwests (initial shear plane area, A = 116 cm²) for an unsaturated stiff fissured clay had been shown to fall between those given by in situ wedge shear tests (A = 900 cm²) and shear box tests (A = 32 cm²), the undrained angle of friction remaining almost constant in each case. In this paper, the possible use of the cylwest in obtaining the relationship between A and the undrained cohesion in unsaturated fissured clays is discussed. The cylwest has the advantage of enabling compacted soils to be tested without being removed from the mould in which they have been compacted, along planes fairly relevant to the slope stability of embankments. For compacted clays, it is shown that two cylwests, performable in about the same time as required for a single unconsolidated - undrained triaxial test, are adequate to define both the cohesion and the angle of friction with sufficient accuracy for practical purposes. The results of cylwests on compacted gravelly sands have been published elsewhere. Presented in this paper, are the results of studies conducted for comparing the results of cylwests (A = 170 cm²) on compacted clays with those given by shear box tests along similarly oriented planes, and for illustrating the usefulness of the cylwest in studying the shear strength of compacted clays.

Keywords: clay, degree of compaction, dynamic compaction, laboratory equipment, pore water pressure, sand, shear test, static compaction, shear box test, slope stability, triaxial test, wedge shear test.

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