Experimental Study on the Effect of Offset Notch on Fracture Properties of Rock under Three‐Point Bending Beam

Abstract

To investigate the effects of offset notch on the fracture properties of rock beam under bending load, granite beam specimens with “one single offset notch” and “central and offset double notches” are made. A series of three-point bending beam tests on the specimens are carried out by controlling the displacement rate of central notch. The whole load-displacement (P-CMOD) curves are obtained. Experimental results show that the larger the distance between the offset notch and beam central is, the larger are the peak load and nominal strength of the specimen. The peak load and nominal strength for the “central and offset double notches” specimens are both larger than those for the “single central notch” specimen. A fracture model considering the effect of offset notch is developed, and the relationship between the offset notch parameter, tensile strength, and fracture toughness is established.

Modelling the Crack Initiation and Propagation of Notched Rock Beam under the Three‐Point Bending Load

“…Figure 11 illustrates the comparison of peak loads from the numerical simulations and experiments [15]. It can be seen that the peak load is close to linearly increase with the increase of the notch offset ratio for both experimental and numerical results.…”

“…e span length is 127 mm. e geometric parameters of the beam keep the same as the granite beam from the experiments [15]. e offset ratio for describing the location of offset notch is expressed as follows:…”

“…Dong et al [6] investigated the fracture properties of rock-concrete interfaces by making a notch at the geometric center of the rock-concrete beam and found the fracture energy of the interface was much smaller than that for concrete or rock. Furthermore, the fracture of rock beam with offset notches attracted more attention for understanding the nominal strength and crack patterns for offset notched rock under the three-point bending load [14][15][16][17]. Zuo et al [14] employed the scanning electron microscope to investigate the effect of the offset notch on the cracking of basalt beam with dimensions of 25 mm × 10 mm × 5 mm.…”

“…Luo and Gong [19] carried out a series of single cyclic loading-unloading flexural fracture tests on marble, red sandstone, and granite and proposed flexural energy storage coefficient and flexural energy dissipation coefficient to represent rock capacities for storing energy and dissipating energy, respectively. Guo et al [15] made granite beams with single center notch and offset notch with dimensions of 145 mm × 50 mm × 18 mm and carried out three-point bending tests. ey found that the larger the offset ratio was, the larger the peak load and nominal strength of the specimen were [15].…”

“…Guo et al [15] made granite beams with single center notch and offset notch with dimensions of 145 mm × 50 mm × 18 mm and carried out three-point bending tests. ey found that the larger the offset ratio was, the larger the peak load and nominal strength of the specimen were [15]. Xu and Cao [17] carried out three-point bending tests by rock-like material beams with single offset notch at different locations and found that the peak load increased linearly with the increase of the offset ratio.…”