Effect of water contents and initial crack lengths on mechanical properties and failure modes of pre-cracked compacted clay under uniaxial compression

Abstract

This study investigated the effect of different water contents (w) and initial crack lengths on the mechanical properties (i.e., the unconfined compressive strength (UCS), deformation modulus, and mode II fracture toughness (KIIC)) and failure modes of pre-cracked compacted clay under uniaxial compression. In this study, 44 intact specimens and 72 pre-cracked specimens with different water contents (18%, 23%, and 28%) and initial crack lengths (0, 15 and 20 mm at 45°, i.e., the angle at which the maximum shear stress acts on the initial crack surface). The results showed that the UCS decreased with a long initial crack or high-water content. In contrast, the deformation modulus depends on water contents, but not on the initial crack length. KIIC was calculated. It was found to depend on the water content. Empirical correlation formulas between KIIC vs. w and KIIC vs. UCS were obtained. Furthermore, the failure modes of the compacted clay were classified into five types. In some specimens, wing cracks propagating from the initial crack disappeared due to contact and gliding of the crack surface by the shear stress, and only secondary cracks were observed at failure.