New method for determining the Mode-I fracture toughness of shotcrete: edge notched partial disc test

Abstract

Fracture toughness (first mode) of shotcrete samples was obtained employing Edge Notched Partial Disc (ENPD) type specimens. Notched Brazilian Discs (NBD) were also used in order to validate the results of the conducted ENPD experiments. Moreover, a numerical analysis was conducted on the ENPD tests to verify the correctness of the measured fracture toughness values compared to numerically obtain ones. Notch lengths in ENPD were set to 15, 30, 45 and 60 mm. However, the lengths of Notches in NBD were set to 10, 20, 30, 40, 50 and 60 mm. The findings reveal that the flat joint model could accurately determine the potential crack growth path and crack initiation stress compared to experimentally obtained results. It was also deduced that the fracture toughness remained roughly the same by enlarging the length of the notch. Moreover, tensile strength and fracture toughness of shotcrete samples are meaningfully correlated (σt =7.92 KIC). ENPD test yields the lowest fracture toughness because of pure tensile stress distribution on failure surface. It also was also determined that the derived fracture extension patterns from the laboratory investigations are in an acceptable agreement with the numerical simulations’ outputs.