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Taking Nanliang Coal Mine thick seam spacing mining as the engineering background, aiming at the safety problem of dynamic rock pressure occurring when the lower coal seam is mined over the pillar of the overburden goaf, this paper studies the mechanism of rock pressure appearing when the working face crosses the pillar of the overburden goaf by means of physical similarity simulation experiment, theoretical analysis and field measurement. Based on the structure and movement characteristics of overlying strata crossing the coal pillar, the mechanical structure models of load calculation of coal pillar and failure and instability of key rock blocks are established respectively, and the resistance of support increases sharply when the coal pillar is located in the working face. Combining with the concrete conditions of the working face passing through the coal pillar, the measures for adjusting the inclination of the working face are proposed, and the field engineering application is carried out. The field monitoring results show that the prevention measures have obvious effect on preventing dynamic rock pressure during passing through coal pillars.

A new method using gradient boosting regression tree(GBRT) which is optimized by logistic regression(LR) to predict working resistance of hydraulic support is proposed, avoiding shortcomings of current determining methods. Add learning rate to GBRT to limit the learning rate of sub-models and prevent over-fitting; using LR to optimize sample parameters to establish LR-GBRT regression prediction model; the model is applied to predict resistance of hydraulic support, and the prediction result is compared with linear regression(LR), support vector model(SVM), decision tree regression(DTR), elastic net regression(EN). The results show that the model has better generalization performance and higher prediction accuracy. It can effectively predict resistance of hydraulic support .