Experimental determination of double-K fracture parameters of concrete under water pressure

Abstract

The wedge splitting test was carried out to experimentally study the initiation, propagation and unstable fracture of crack in concrete under mechanical loading combining with water pressure. In order to obtain the true load-crack mouth opening displacement(CMOD) curve in the process of loading, the specimens experienced the cyclic loading-unloading process of water pressure under the mechanical loading until fracture occurred. Two modes of loading control for test including maintaining the CMOD as constant and keeping the mechanical loading as constant were adopted to avoid the effect of water pressure. The variation of crack was monitored by means of strain gauges. The experimental data were compared with the calculated unstable fracture toughness and cohesive toughness as well as the initial fracture toughness based on double-K criterion for crack propagation of concrete. The result shows that the cyclic loading of water pressure accelerates the development of cracks and results in obvious decrease of the maximum bearing capacity of concrete.