Notch effect and fracture load predictions of rock beams at different temperatures using the Theory of Critical Distances

Abstract

ABSTRACT: This work aims to analyse the fracture behaviour of rocks with U-shaped notches subjected to mode I loading and to different temperature conditions. To this end, the so called Theory of Critical Distances (TCD) is applied and four different types of isotropic rocks are studied: a Floresta sandstone, a Moleano limestone, a Macael marble and a Carrara marble. This study attempts to extend a previous work of the authors where the TCD was successfully applied to U-notched components subjected to mode I loading conditions at room temperature. In this case, the effect of temperature is considered as a new variable. The research comprises, in total, more than 790 four-point bending tests and 144 tensile splitting (Brazilian) tests. The latter include 6 disc-shaped specimens for each rock and temperature (6 different temperatures), while the four-point bending tests consist of at least 6 SENB specimens for each rock, notch radius (8 different notch radii varying from 0.15 mm to 15 mm) and temperature (4 different temperatures) combination. The temperatures considered in this study vary from room temperature up to 250ºC, which is a common range in geothermal applications. Temperature has proven to be a significant parameter when analysing the fracture behaviour of the four selected rocks. Its influence on the tensile strength and fracture toughness of the rocks is clear and reveals common patterns. However, no apparent tendencies are shown on the influence of temperature on the critical distance (L). Likewise, the application of the TCD has led to relatively accurate fracture predictions and notch effect analyses at different temperature conditions.