Extraction of Marble Blocks by Controlled Blasting Techniques-A Case Study

摘要

Blasting needs of marble is entirely different than conventional methods of blasting The principle objective is to develop cracks in the rock so as to dislodge it from the surrounding rock without causing damage to it or to the remaining rock Conventional drill and blast techniques have proven to be disadvantageous and have law recovery of blockable marble. In addition to this micro cracks develop in the remaining rock Hence introduction of controlled fracture growth technique has important role in development of marble extraction techniques. A field study was carried out in white marble and pink marble mines. In this paper existing practices are analysed. New practices were introduced to reduce the cost of extraction and also to improve recovery of blockable marble by controlling fracture growth in desired direction. Field study showed that in D-cord splitting method, spacing between holes ranges from 0.08m to 0.30m whereas result of experimental trial using notched hole technique showed that hole spacing can be extended from 0.33m to 0.72m. On comparison it is clear that cracks in the desired direction upto almost five times greater distance can be achieved by using prenotched blast hole technique as compared to D-cord splitting technique. By use of prenotched blast hole technique the extraction cost can be substantially reduced.