Abstract: During the blasting and the deep excavation for foundations in welldeveloped karst areas, the vibrations by the blasting might cause the cracks of the rock cavities to expand and break, and then lead to the collapse of the karst cavities, it may also cause serious engineering safety hazards. Based on the blasting vibration monitoring, this paper studies the impact of vibrations generated by blasting excavation of the foundations in urban karst areas on the surrounding environment and the stability of karst cavities. And the attenuation pattern of the blasting vibration at the site is studied. This paper also investigates the reasonable cavity treatment plan and blasting construction plan. The results show that the stability analysis of the cavity under the blasting vibration is performed by using the chamber stability method for evaluating the flexural and shear strength of the roof respectively. Based on the vibration monitoring data of the protection object and the supporting structure, the corresponding empirical formula of the peak vibration velocity attenuation is obtained. The site coefficient K and the attenuation index α in the formula are negatively correlated with the hardness of the propagation medium. For the karst (soil) cavities around the deep karst excavation and below bottom of excavation, the corresponding karst treatment scope principles and measures are determined.

Key words: Karst Rock Cavities, Deep Excavation, Blasting, Vibration, Vibration Attenuation Pattern