LAUSR

Abstract This work presents experimental data to determine the apparent fracture toughness, K Q , from hydraulic fracturing in a penny-shaped crack for frozen sand. An initial crack, represented by a circular plastic, is embedded in the specimen during the preparation with a pipe positioned perpendicular to the center of the circular crack in order to inject liquid into the penny-shaped crack. In determining the K Q , the first approach directly utilizes the penny-shaped crack stress-intensity factor (SIF), which requires the hydraulic pressure and crack radius dimension. The second approach combines the volume in the penny crack with the SIF, in which K Q is determined without using the crack radius dimension. The third approach (brittleness) explores the stress in the uncracked ligament to estimate the tensile strength ( σ t ) and characteristic length ( l c h ), which is related to the apparent fracture toughness. The K Q from these hydraulic fracturing approaches are validated via three-point bend (TPB) on notched and unnotched beams for frozen sand, using the same dimensions and preparation method. The hydraulic fracturing experimental results indicated that the values of K Q , σ t , and l c h for frozen sand are 0.22–0.66 MPa√m, 7.5–9.5 MPa, and 0.8–7.6 mm, respectively, which are comparable to the TPB results. An important outcome of this work allows for the determination or estimation of K Q , σ t and l c h for a material like methane hydrate in sand that is difficult to obtain using the standard test setup under the atmospheric conditions.