ROCK MASS CLASSIFICATION FOR LIMESTONE IN TOPICAL CLIMATE FOR BLASTING

Tropical climate has the impact of different degree of weathering on limestone which results in variation in geo-mechanical strength. Intact rock properties and discontinuity structure have a direct correlation with blast ability index. Tropical limestone quarries from Thailand and Cambodia are selected for this study for assessment of rock mass classification for blasting purpose scuh as blast ability index (BI). For working quarry in Thailand, Geological strength index (GSI) classification system is used to classify rocks which are useful for blast design. For developing a quarry in Cambodia where geological information is not available during the initial stage of the mining project, rockmass assessment is done based on exploration data consisting of Rock quality designation (RQD), the percentage of cavities, lithology, and hardness. 99 percentage of cavities in the karst limestone of Cambodia are found with argillaceous limestone and upper cherty limestone. Based on cavity classification, 74 percentage of drilling area has average cavities of 0.37 percentage which is the least. 9 percentage of drilling area has greater than 20 percentage of cavities or 2 percentage of total area which is highest and concern for blast performance from fly rock, fragmentation and back break point of view.

BI, Tropical limestone, Karst limestone, RQD, GSI