Parametric Study on the Stability of Crown Pillars Considering MultiVariate Regression and K-Cross Validation Techniques

The role of crown pillar between two main levels in any underground metalliferrous mine plays a pivotal role in maintaining the stability of extracted open stopes in each level.Thus, the dimension of the crown pillar left intact between the main levels in the underground should be competent enough to withstand the induced stresses developed as a result of extraction as well as blasting, especially in large scale production methods such as large-diameter blasthole stoping method.In addition to the crown pillars in adjacent levels, a barrier crown pillar of sufficient thickness is also left intact between the ultimate pit bottom and the first level of extraction.These horizontal pillars are of utmost importance as it is one of the deciding factors in determining the stability of the existing underground structures throughout the life of mine.The present study focuses on the stability of a crown pillar left intact between two main levels existing below an open pit mine operating simultaneously with the underground mine.The targeted proposed production of the underground mine is around 5 million tonne per annum.In this paper, a total of 135 finite element models of the underground mine have been analyzed considering elasto-plastic material model.The simulation models are assessed in terms of plastic damage index with variation in material properties, crown pillar thickness, stope-extraction sequence and depth of mining.Based on the results obtained, some useful conclusions have been drawn considering both multi-variate regression and k-cross validation models.