The resonant frequency measurement and cracking evolution in rocks
Résumé
During a dissolution process, bedding planes and cracks in the sedimentary rock itself enlarge and/or propagate over time. They move the water and expend the conduits through a combination of dissolution and abrasion of the surrounding rock. The ground stability is thus linked to the cracking state of the rock. The measurement of the resonant frequency enables the assessing of the cracking state of a rock. It is a nondestructive method based on the processing of a unit pulse excitation. Since karsts which are near the ground surface undergo climate variations, measurements have been carried out on sedimentary rocks subjected to frost cracking and also on marble samples subjected to heat cracking. The results highlighted the decrease of frequencies with cracking. This measurement thus appears to be an appropriate method to evaluate the cracking state of a rock and also to follow the evolution of the cracks inside the rock.