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.
Highlights
It is hard to know the postpeak behavior of rock through the Brazilian disc test. e direct tensile test is an ideal method for obtaining the whole stress-displacement curve for rock [4, 5]
Erefore, the three-point bending beam test has been an effective method for obtaining rock fracture properties through the whole load-crack mouth opening displacement (P-CMOD) curve [6,7,8,9]
The load linearly increases with increasing CMOD, which can be regarded as the linear elastic stage. e difference of the linear elastic stage in the figures is mainly caused by the different porosities of the samples
Summary
Rock fracture is one of the most important topics on rock mechanics, which dominates rock projects failure such as dam instability, landslide, and tunnel collapse [1,2,3]. e macrofailure of rock mass is caused by microcracks initiation, coalescence, and propagation. e fracture properties of rock are attracting more attention for understanding the fracture behaviors of different rock types under different external loads. E direct tensile test is an ideal method for obtaining the whole stress-displacement curve for rock [4, 5]. Erefore, the three-point bending beam test has been an effective method for obtaining rock fracture properties through the whole load-crack mouth opening displacement (P-CMOD) curve [6,7,8,9]. [17] developed a numerical method to investigate the effect of particle size on rock fracture under the three-point bending test. Most existing research studies on the three-point bending test were carried out on single notch beam, and the effect of initial cracks on rock fracture was rarely evaluated [11,12,13,14,15,16,17,18,19]. The relationships between the tensile strength and fracture toughness and offset notch parameter are formulated
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