Estimation of the first roof weighting interval incorporating roof strata cavability

The interval of the first roof weighting in mechanized longwall mining is directly related to the applied loads on the support system and, hence, have an important role on the stability, safety and continuity of operation. This paper presents an approach based on the cavability of immediate roof to estimate the first roof weighting interval. For this purpose, the roof strata cavability index (RSCi) was defined with the aim of integrating the effective parameters on the roof caving process. RSCi was developed as the output of a new classification system using a fuzzy hybrid multi criteria decision-making technique. After that, the relationship between RSCi and extracted volume until the first caving moment (i.e. the product of extraction height in the panel width in the first roof weighing interval) was determined using linear and non-linear regression models. The models were proposed and validated using a database included surveyed and collected data of twelve actual cases from six countries. Results indicate that the quadratic polynomial degree 2 model possesses a higher performance in the estimation of the first roof weighting interval when compared to the other models. From this paper can be concluded that the proposed approach has an acceptable accuracy and flexibility as well in the estimation of the first roof weighting interval in longwall coal mining projects.