Search

In order to solve the prediction problem of water inrush from coal seam floor, a prediction model of water inrush from coal seam floor based on principal component analysis and Logistic regression method was proposed. Through the analysis of the risk factors of floor water inrush, six variables, including the thickness of the aquifers, the pressure of confined water, the fall of the fault, the distance between the fault and the working face, the mining height of the coal seam, and the dip angle of the coal seam, are selected as the initial impact indicators to study the floor water inrush. First, the principal component analysis method is used to reduce the dimensions of the original index data, and the established Logistic regression model is used to analyze and predict the data. Then, five groups of sample data to be tested are used to verify the model. The results show that the comprehensive prediction accuracy of the model for water inrush samples reaches 90% at the highest, and the prediction accuracy reaches 80% when the data to be measured is used for back judgment, which shows that the prediction model has certain reliability and can be used as a new method for predicting water inrush from coal mine floor.

In order to investigate the microstructure uniformity and plasticity of hot-rolled 0Cr21A16 alloy sheet and im prove its high temperature and cold working characteristics， heat treatment tests and microstructure properties analysis were carried out at different temperatures. The microstructure and mechanical properties of 0Cr21Al6 alloy sheet before and after heat treatment were studied by optical microscopy， X-ray diffraction （XRD）， Gleeble high temperature thermal tensile test， scanning electron microscopy （SEM） and nanoindentation. The results show that the microstructure unifor mity of 0Cr21Al6 alloy sheet can be improved by heat treatment， and the average grain size is about 42 μm after holding at 960 ℃ for 6 min 40 s， and the overall grain size is relatively uniform and fine compared with at 940、980、1 000、1 020 ℃ heat treatment， the hardness and plasticity are the best combination， and the fracture toughness KIC is the best after 960 ℃ heat treatment. With the best comprehensive performance， it can effectively avoid the brittle fracture of materials in the production process. In addition， Gleeble test shows that the heat treatment temperature over 1 000 ℃ is no longer suitable for hot processing.