The spatial distribution of excavation damaged zone around underground roadways during blasting excavation

摘要

Knowledge of the degree and depth of the excavation damaged zone (EDZ) resulting from drill-and-blast excavations hasimportant influences on the design and construction of deep underground tunnels. However, the spatial distribution of EDZaround underground tunnels subjected to the combined effect of blast loading and in situ stress unloading is still underdiscussion. In this study, the dependences of the spatial distribution of EDZ in an underground tunnel on the variations ofin situ stress conditions, excavation dimensions and rock strength were investigated using a combined method of fieldmeasuring and numerical modelling. Field measurements of EDZ in an underground mine were first conducted using thenon-metallic acoustic technique. Subsequently, a blast excavation model concerning the combined effect of blast loading andin situ stress unloading was developed and calibrated against the field-measured data. Finally, the EDZs induced by variousin situ stress conditions, tunnel shapes, and dimensions as well as rock strengths were simulated. The field measurementresults indicate that larger highly damaged zones are generated at the roadway crown and sidewall, whereas smallerintensively damaged zones are induced at the roadway shoulder. The average depth of EDZ around the tested roadways, withan overburden of 355 m to 915 m, varies from 0.36 m to 1.72 m. The numerical results show that in situ stress, excavationdimension, and rock strengths significantly impact the depth of EDZ. More specifically, lateral pressure coefficient and theshape of the roadway cross section play a predominant role in controlling the distribution pattern of EDZ, and the magnitudeof in situ stress, excavation dimension, and rock strength mainly contribute to the depth of EDZ. Furthermore, the specialphenomenon of zonal disintegration in the surrounding rock mass occurs around highly pre-stressed underground roadways.