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ORIGINAL PAPER

Failure characteristics of brittle rock-like specimen with fractured internal structure under uniaxial compression Yusong Zhao 1

&

Yongtao Gao 1 & Shunchuan Wu 1,2 & Congcong Chen 1

Received: 9 July 2019 / Accepted: 20 August 2020 # Saudi Society for Geosciences 2020

Abstract The methods commonly used to prepare fractured structures can be used to form only 2D cracks or holes in rock specimen. In engineering, however, the geological structures considered usually have prominent 3D characteristics. To prepare specimens with 3D internal structures, a method to form real cavity in a hard-brittle rock-like model is proposed in this paper. The uniaxial compression test was then conducted on it using three cylinder samples (solid, internal fracture, and internal cavity), and main conclusions were obtained: (1) By using the volume loss method and super absorbent polymer as material in a small-scale laboratory test, rock-like samples with internal open-type flaws and cavities were prepared such that they were not in contact with the outer surfaces of the samples. (2) The results of the compression test show that the internal fractures reduced the uniaxial compressive strength as their volume increases. However, the size of the internal fracture had little influence on the elastic modulus and peak-time axial strain of the samples over a certain range. (3) Unlike the final failure surface obtained in 2D studies, the splitting surfaces shown in this test always extended diagonally with respect to the internal structures and were vertical to the preset fractures. (4) Because the horizontal section of the internal cavity/flaw was square in shape (the diagonals were perpendicular to each other), the direction of extension of the tensile failure surface was not along the horizontal diagonals of the internal structures but perpendicular to the corresponding diagonals. Keywords Rock-like sample . Internal fracture structure . Uniaxial compression test . Super absorbent polymer

Introduction Fractured rock mass is among the most common geological structures in civil engineering, mining engineering, and

Responsible Editor: Zeynal Abiddin Erguler * Yongtao Gao [email protected] Yusong Zhao [email protected] Shunchuan Wu [email protected] Congcong Chen [email protected] 1

School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China

2

Faculty of Land Resource Engineering, Kunming University of Science and Technology, Kunming 650093, Yunnan, China

underground space engineering, where its structure determines the risk of failure. Many researchers have conducted extensive laboratory tests to study the characteristics and procedures of crack initiation, propagation, and coalescence, and some classical test designs are as follows: Bobet and Einstein (Bobet 2000; Bobet and Einstein 1998) used rock-like specimens to study the processes of fracture coalescence in two parallel 2D prefabricated cracks using uniaxial and biaxial compression tests. By using a