In Situ Field Testing for Fracture Properties of Dam Concrete

Abstract

Fracture toughness tests on large‐scale cubical concrete specimens, with maximum size aggregate ranging from 19–76 mm (0.75–3.0 in.), are conducted under laboratory conditions. The laboratory experiments are based on the pressurization of a borehole and measurement of diametrical changes. During the experiments, acoustic emissions (AE) are monitored and recorded to indicate concrete cracking. Based on the AE bursts, the pressurization of the borehole is performed in a controlled manner. Field conditions are simulated with borehole coring and applied uniaxial confining stresses. Values of an apparent fracture toughness are determined from the experimental data and compared with the results of fracture tests performed on large wedge‐splitting specimens. Following the laboratory experiments, a field test on a concrete gravity dam is conducted using the experimental methodologies developed in the laboratory. In situ fracture parameters of the dam concrete are determined. Based on the laboratory and field tests, the apparent fracture toughness values are concluded to be dependent on the confining stresses.