Determination of dynamic rock Mode-I fracture parameters using cracked chevron notched semi-circular bend specimen

Fracture Propagation in Brazilian Discs with Multiple Pre-existing Notches by Using a Phase Field Method

“…The initiation and propagation of multiple cracks significantly affect many rock engineering problems, such as rock cutting, hydraulic fracturing, and explosive fracturing [1]. In the past decades, crack propagation in rocks has received attentions from many researches [2][3][4][5], among which many novel tests were applied to investigate crack patterns under compressive loads, such as the notched semi-circular bending tests (NSCB) [6], the cracked chevron notched semi-circular bending method (CCNSCB) [7], and the Brazil splitting tests [8]. …”

Numerical Investigation of Dynamic Rock Fracture Toughness Determination Using a Semi-Circular Bend Specimen in Split Hopkinson Pressure Bar Testing

“…In these cases, rocks often damage under a rather high loading rate, and, thus, the dynamic characteristics of rocks differ significantly from their static counterparts. To determine the fracture toughness of rocks under high strain rates, the split Hopkinson pressure bar (SHPB) or Kolsky bar system has been widely used in conjunction with several sample configurations commonly extended from static fracture tests, including cracked straight-through Brazilian disk (CSTBD) , cracked chevron notched Brazilian disk (CCNBD) (Dai et al 2010a), short rod (SR) (Zhang et al 2000), single edge notch bending (SENB) , notched semi-circular bend (NSCB) (Chen et al 2009;Dai et al 2010b;Zhang and Zhao 2013), cracked chevron notched semi-circular bend (CCNSCB) (Dai et al 2011), etc. Among these methods, the NSCB specimen in combination with SHPB techniques has been recommended as the suggested method for determining mode I dynamic fracture toughness of rock materials by the International Society for Rock Mechanics (ISRM) in 2012 (Zhou et al 2012), due to its distinct advantages such as easy sample preparation from core-based rock mass, simple loading, as well as easy adaptability to anisotropy studies, etc.…”

Three-dimensional numerical evaluation of the progressive fracture mechanism of cracked chevron notched semi-circular bend rock specimens

“…The ISRM suggested CB method and SR method [29] and CCNBD method [13] fall into this group II. The cracked chevron notched semi-circular bending (CCNSCB) method, originally initiated by Kuruppu [4] and later developed by Dai et al [5], appears to have retained the merits of the ISRM suggested CCNBD method [13] and the ISRM suggested NSCB method [30] and [31] such as larger number of core specimens can be prepared by halving the cores, simple specimen installation and loading fixture, adaptation of high strain rates, easier sample preparation, and availability of pure or mixed mode (Mode-I and Mode-II) fracture studies of rock materials. In addition, this CCNSCB method overcomes major weaknesses of the CCNBD method [13] and the NSCB method [30,31].…”

“…Myriads of methods with varying sample configurations have been adopted in rock fracture toughness measurements including Brazilian disc (BD) method [1], notched semi-circular bend (NSCB) method [2] and [3], cracked chevron notched semi-circular bend (CCNSCB) method [4][5][6], cracked straight through Brazilian disc (CSTBD) method [7][8][9][10][11], cracked chevron notched Brazilian disc (CCNBD) method [12][13][14][15][16], diametric compression (DC) test [17], double edge cracked Brazilian disc (DECBD) method [18], edge crack triangular test [19], flattened Brazilian disc (FBD) method [20], hollow center cracked disc (HCCD) method [21], holed-cracked flattened Brazilian disc (HCFBD) method [22], holed-flattened Brazilian disc (HFBD) method [23], modified ring (MR) test [24], radial cracked ring [25] and [26], straight edge cracked round bar bend (SECRBB) http angle of friction method [27] and straight notched disk bending (SNDB) method [28]. At present, there are no standard methods of measuring Mode-I fracture toughness of rocks; only four suggested methods are proposed by International Society of Rock Mechanics (ISRM), namely chevron bending (CB) method and short rod (SR) method [29], CCNBD method [13] and NSCB method [30] and [31].…”