Investigation on crack evolution behaviors and mechanism on rock-like specimen with two circular-holes under compression

Studying crack evolution behaviors and mechanism of the holed concrete specimens is very significant for civil building and underground engineering. Currently available literatures are mainly focused on the mechanical and failure behaviors of pre-holed rock or rock-like materials, less on the crack evolution behaviors and mechanism. In this paper, uniaxial compressive tests were carried out on the concrete specimen with two circular-holes by rock testing machine combined with digital image correlation (DIC) and acoustic emission (AE) systems. The interacting tangential stress was further solved on two circular-holes under uniaxial stress by a new analyticalnumerical method. Research results show that the presence of the circular-hole usually results in the larger degradation of mechanical parameters of the concrete specimens compared to the intact concrete specimen. Specimen with two vertical circular-holes has larger mechanical parameters than that only with one circularhole. Concrete specimen with the two circular-holes under compression usually presents the crack evolution with primary tensile cracks appearance followed by slabbing cracks, and finally remote tensile or shear cracks away from the circular-holes. When the orientation angle alpha between the connecting line of two circular centers and the horizontal direction is smaller (alpha = 0 degrees, alpha = 30 degrees), crack coalescence never takes place between two circular-hole, while with the increase of alpha (alpha = 60 degrees, alpha = 90 degrees), the two circular-hole coalesces with each other along the loading direction, with different coalescence mechanism. The theoretical results suggest that both the number and arrangement of the circular-holes have a pronounced effect on the tangential stresses, and the mechanism of crack evolution can be well illustrated by the tangential stresses around the two circular-holes.