Experimental study of the influence of the filling material on the mechanical properties of marble with holes

As a natural material, stone can suffer from initial damage (such as bedding and microfracture) during the diagenetic stage and rock defects (such as joints and faults) are formed after diagenesis. Under the influence of these defects, the properties of rock strength, deformation, and failure will also change. Studying the mechanical characteristics of defective rock can truly reflect the actual situation in the field. For the original hole fissures, actual rock engineering often contains fillings that decrease the stress concentration of the surrounding area of the hole; according to the type of filling, the filling can withstand the corresponding pressure. Thus, it is necessary to study the influence of the filling on the mechanical properties of porous rock damage. To study the influence of the filling material on the mechanical properties and the deformation and failure characteristics of the hole-bearing rock (with each specimen containing one hole), hole-bearing marble (with each specimen containing one hole), and plaster filling, the appropriate specimens were prefabricated in an indoor environment. The law of crack propagation of the specimens was analyzed based on the results of the uniaxial compression and acoustic emission tests and the results of CT scanning of the specimens before and after failure. The results are given as follows:(1) In comparison with hole-bearing marble, the peak stress of the marble specimen with the filled hole increases by 10.62%. Before the peak stress of the specimens, the pre-peak features are similar, and both specimens exhibit a stress reduction phenomenon; however, the post-peak characteristics are different, and the characteristics of partial deformation are more obvious. (2) After the peak stress phase, the acoustic emission features of the perforating hole in each hole-bearing specimen are more remarkable, and the crack propagation is more rapid than those of the gypsum-filled specimens, indicating the gypsum filling stems the crack expansion of the specimens. (3) A difference is found between the destruction model of the marble specimen with a hole and that of the marble specimen with the hole filled with gypsum. Each crack is relatively single for the specimen of marble with a hole, and main cracks exhibit tensile damage; moreover, wing cracks are more developed in the end, and some of those cracks propagate toward both sides, resulting in a block falling off. However, cracks around the hole are thinner and more dispersed, forming "X" shear damage because of the mutual crossing of the cracks.