Ground Vibrations in Opencast Mine Blast on Structures Vis-À-Vis a Local Environmental Effect and Its Mitigation Through Mining Technology

Abstract

This paper presents part of the work on ground vibrations induced by blasting, and to estimate safe maximum charge per delay to protect the nearby structures. Blasting near sensitive areas has always been a cause of concern and utmost care has to be taken to keep the charge per delay below the stipulated level A number of field visits were made to collect the geotechnical data, and monitoring ground vibrations induced by blasting. A number of blasts were monitored to study various blast parameters related to blasting Overburden and Coal benches and to understand the effect of blast on the surrounding structures, and rock mass conditions at the mine site. Drilling is accomplished by tire mounted drill machine capable of drilling large diameter holes of 159mm. The drilling pattern of the mine benches is based on the rock formation of the particular bench and varies with the variation in strata from 4 m to 6 m. Holes were charged with Bulk Emulsion Explosives in association with Booster(Cap sensitive). Nonel systems of initiation were used to reduce vibration. Accordingly, the safe charge per delay for the distance of 100 m, 200 m, 300 m, 400 m, and 500 m is 18.9 Kg, 75.9 Kg, 170.8 Kg, 303.7 Kg, and 474.5 Kg, respectively to keep the vibration level below 5 mm/sec for the above geomining conditions of Jindal Power Opencast Coal Mine- Tamnar. The damage criteria was proposed by many organizations including USBM, DGMS, Indian Standards etc based on the Permissible PPV in mm/s and Frequency of the ground vibrations for various types of structures. The criteria based on the Permissible PPV in mm/s and Frequency of the ground vibrations for various types of structures was presented. In the present investigations safe charge per delay 3 was estimated through empirical model to limit the ground vibrations within safe limit of 5 mm/sec considering the structures as sensitive and not belonging to the owner. Hence, the mining technology in terms of blasting pattern and explosive charge was recommended for local environmental protection of the structures.