Experimental study on the evolution characteristics of dynamic load of hydraulic support top beam during coal caving

Contact coal-gangue identification requires studying the bearing characteristics of hydraulic support top beams in fully mechanized top coal caving. However, existing research primarily focuses on the bearing characteristics of supports before and after coal caving or the mechanical response characteristics of supports under given loads, neglecting an in-depth exploration of load changes during the coal caving process. To address this issue, a dynamic load similarity simulation test platform for top-coal hydraulic supports was established, using granular particles to simulate broken coal gangue. This setup simulated the coal caving process in a fully mechanized working face, and thin-film pressure sensors were employed to collect pressure data from the support top beams. The dynamic load evolution characteristics of the support top beams during the coal caving process were analyzed. The experimental results indicated: ① The caving of top coal significantly affected the load on the support top beams, demonstrating an evolution pattern where the overall load first increased, then decreased, and finally stabilized as the top coal was released. ② Along the length of the beam, the locations of the support top beams farther from the protective beam were less affected by the caving of top coal. This was primarily reflected in the smaller increase in peak load compared to the initial value at locations farther from the protective beam, as well as a longer time required to reach the peak load. ③ Along the width of the beam, due to the constraints of boundary conditions or the unevenness of the flow process during top coal caving, the peak load at different positions of the beam showed variability, with the maximum increase in peak load compared to the initial value reaching up to 2.4 times the minimum increase.