Blast-induced rock damage control in Fangchenggang nuclear power station, China

In the process of blasting excavation, stress wave propagation and gas expansion can basically induce damage to surrounding rocks, which is detrimental to rock mass integrity and engineering safety. In this case, evaluation and control of blast-induced effects are essential to the safety of nearby buildings and integrity of bedrock in blasting field. In Fangchenggang nuclear power station of China, the drill-and- blast method was employed for bedrock excavation. In order to reduce the blast-induced damage zone, the wave propagation and associated damage to rock mass should be carefully investigated. In this paper, the wave propagation regressively obtained from field monitoring data was presented based on empirical formula （e.g. Sadovsloj formula）. The relationship between the peak particle velocity （PPV） at a distance of 30 m away from the charge hole and charge per delay in blast design was derived. Meanwhile, the acoustic tests before and after blasting were conducted to determine the damage depth of rock mass. The charge per delay in blast design was then calibrated based on the blast-induced wave propagation regularity. The results showed that a satisfactory effect was achieved on blast-induced damage control of rock mass. This could be helpful to rock damage control in similar blasting projects.

On the Foundations of the Ultrasonic Non-Destructive Determination of Stresses in Near-the-Surface Layers of Materials： Review

The foundation of the ultrasonic non-destructive determination of stresses in near-the-surface layers of solids is presented. The method is based on the regularities of Rayleigh wave propagation in solids with initial （residual） stresses. A description of the above mentioned method and examples of stress determination are presented. Examples are considered as applied to the residual stresses arising at electric welding and the operating stresses arising at loading.