An innovative approach to theoretical analysis of partitioned width & stability of strip pillar in strip mining

The strip mining method is preferred to the extraction of coal resources under surface buildings, water bodies and railways in China. Strip pillars with appropriate widths play a significant role in controlling stress distribution and surface subsidence. The strip mining activity at Tangkou coal mine in Eastern China is taken as the engineering background in the paper. In order to evaluate the general strip pillar design of mining area no. 430, an innovative analytical model is developed to determine the yield width and the elastic core width of the strip pillar under the stress superimposition effect in this paper. In the proposed model, the strip pillar is divided into the yield zone and the elastic core zone on the basis of the existing reasonable structural division of the strip pillar. Based on the Drucker-Prager criterion which considers the influence of the intermediate principal stress, the formulae of the partitioned width of the strip pillar are inferred. The yield width of the strip pillar with one-sided goaf is derived based on the limit equilibrium theory and the Drucker-Prager criterion. The yield width of the strip pillar with two-sided goafs is obtained based on the stress superimposition method. The elastic core width of the strip pillar is obtained by the semi-inverse method with the consideration of mine pressure and the application of the Drucker-Prager criterion. As a case study, the proposed model is used to determine the yield width and the elastic core width of the strip pillar at Tangkou coal mine in China. Comparing the obtained results with the in-situ measurement data, it can be concluded that the proposed analytical model is effective in calculating the yield width and the elastic core width of the strip pillar. In order to evaluate the effects of the parameters in the proposed model on the yield width of the strip pillar with one-sided goaf and the elastic core width of the strip pillar with two-sided goafs, a detailed sensitivity analysis is conducted based on the actual data at from Tangkou coal mine.