Dynamic caustics test of blast load impact on the group of crack surrounding neighboring roadway
Guo Dong-min · Meitan xuebao · 2014
In order to research the influence of blasting vibration from excavation of a new tunnel on close-in existed tunnel which contains defects in the surrounding rock,based on digital laser dynamic caustics experimental system which uses explosive to apply the load,the authors explored the expansion laws of the original crack group when the new roadway was excavated by blasting. The experimental results show that the propagation of the cracks surrounding the roadway has something to do with the position of the crack,crack angle and the distance L between blast hole and the center of roadway; When L45 mm or L65 mm,it appears the triangle damage on the left side of roadway,but the pattern of manifestation is different. When L increases,the propagation phenomenon of the No. 1,No. 3 and No. 4cracks are not obvious,the displacement of other cracks extension basically shows a trend of gradually diminution;When the group of crack propagates,the dynamic stress intension factor oscillating increases to peak firstly and then decreases,it increases to second peak again and decreases to zero. And the smaller crack eventually expanding displacement is,the more obvious the phenomenon is,the crack presents the extension rule of extension-the crack arrestrapid extension-crack arrest.