Support increasing resistance forms of macroscopic roof support and its prediction model

The roof movement of working face by mining leads to the change of support work resistance. To predict the evolution of the working resistance of support, the mine pressure monitoring data of 2 263 coal cutting cycles in 31201 working face of Shigetai coal mine,13302 working face of Qianshuta coal mine and 5302 working face of Changping coal mine were obtained in this paper. The increasing resistance laws of support in different mining stages for typical roof were investigated. According to the characteristics of resistance increase, the first and second type resistance increasing curve were presented. The generalized Kelvin model and Maxwell model were employed to describe the slow and strenuous movement of macroscopic roof, and the resistance increase prediction model of four area of macroscopic roof was established. Then the support increasing resistance evolution was predicted by the model proposed. The results show ① under typical roof conditions, the resistance increase of supports can be classified into two types of resistance increasing curves. The first type resistance increasing curve is caused by the slow movement of the roof. It is convergent, and the increasing resistance rate is small. The second type of increasing resistance curve is caused by the strenuous roof movement, and the resistance increasing rate is large. ② The probability of the first type and the second type resistance increasing curves during periodic pressure is 38.2% and 61.8%, respectively.③ Then the support increasing resistance evolution can be better predicted by the resistance increase prediction model of four area of macroscopic roof. ④ With the initial support force increasing, the resistance increasing rate and resistance increasing force of the roof all decrease. ⑤ When the resistance increasing curve of the support at the Changping 5302 working face belongs to the first type, the working resistance is less than 11 MN, and the safety valve does not open.When the resistance increasing curve of the support belongs to the second type, the working resistance reaches 11 MN in 6.2 h, then the safety valve opens. To prevent the support crushing, the coal mining and production cycle should be completed within 6.2 hours for 5302 working face.