Journal Published Online: 14 November 2022
Volume 46, Issue 1

Double Plane Direct Shear Apparatus for Determination of Adhesion Factor in Clays

CODEN: GTJODJ

Abstract

A modified direct shear assembly with two parallel shear planes was designed to enable the simultaneous and independent measurement of cohesive and adhesive resistance; it is named the “double-plane direct shear device.” The three-block specimen box of the device has top and middle blocks filled with soil specimen and the bottom block is made of solid steel. The middle box is laterally displaced while restraining the top and bottom box, leading to concurrent shearing along two parallel shear planes. Results from quick undrained testing of kaolinite at five different consistency indexes (Ic) and three different vertical stresses (σv) are presented. The stress–deformation curves show greater mobilization of adhesive stress than cohesive stress at low deformations at all Ic and σv. The deformation required for the complete mobilization of cohesive and adhesive stresses and their variation with Ic and σv is discussed. A parameter crossover deformation (dco) is defined to identify the region where adhesive stress is greater than cohesive stress, which would be useful in applications where soil stickiness is of concern. The results show that the presence of partial drainage increases the dco, which results in an increased deformation range over which adhesive stress is greater than cohesive stress, thereby increasing the stickiness susceptibility. Furthermore, results show that the adhesion factor (α, defined as the ratio of adhesion to undrained cohesion) always stayed below unity under undrained conditions, whereas under partial drainage conditions, values of α greater than unity were obtained. The study concludes that for the application where soil stickiness is of concern, the determination of α and its usage to analyze stickiness susceptibility should be performed under simulation of appropriate drainage boundary conditions.

Author Information

Shetty, Rakshith
Department of Civil and Environmental Engineering, Center for Underground Construction and Tunneling, Colorado School of Mines, Golden, CO, USA
Salas Reyes, Israel
Department of Civil and Environmental Engineering, Center for Underground Construction and Tunneling, Colorado School of Mines, Golden, CO, USA
Cha, Minsu
Department of Civil Engineering, Jeju National University, Jeju-si, Jeju Province, Republic of Korea
Mooney, Michael
Department of Civil and Environmental Engineering, Center for Underground Construction and Tunneling, Colorado School of Mines, Golden, CO, USA
Pages: 24
Price: $25.00
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Stock #: GTJ20220046
ISSN: 0149-6115
DOI: 10.1520/GTJ20220046