..., K . K C determination can be achieved by doing Cracked Chevron Notched Brazilian Disc (CCNBD) tests, which is standardized by the International Society of Rock Mechanics (ISRM), and defines values for fracture toughness for pure mode I fracture propagation ( K IC ). On this mode, fracture occurs...

... wellbore design reservoir geomechanics toughness upstream oil & gas variation fracture mechanism hydraulic fracturing reservoir characterization fracture toughness rock mechanic wellbore integrity propagation gunzburger compression propagate limestone instability experiment...

... inclination angles, namely: 70°,80° and 90° with respect to the vertical axis of the specimen. A Digital Image Correlation (DIC) technique is used to monitor crack initiation and propagation on the specimen surface. The paper discusses experimental observations about the influence of different interface...

... at the tips of horizontal joints, followed by the secondary shear cracks propagating towards the opposite joint. Savilahti (1990) did some further study on the specimens of jointed rock under direct shear tests where the joint separation varies in both horizontal and vertical directions and joint arrangement...

..., and so on r-. ". ., ' In general case. an echelon system of tension cracks forms at first (fig. I). They arise from defects of material structure and propagate along the planes of principal tension stresses. Narrow crushing zones (surfaces) begin to arise at a subsequent increase of shear load T or shear...

... the stresses at the tip of the most critical crack within the body exceed the theoretical strength, causing the crack to propagate. Rather, it has been found that cracking begins in rock at stresses which are considerably lower than the fracture strength, and that fracture itself is a complicated process...