Study on roof movement form and mine strata pressure law of fully-mechanized top coal caving mining in ultra thick seam

In order to have the roof movement form of the fully-mechanized top coal caving mining and the influences to the mine strata pressure law of the coal minin g face,the study was conducted with the similar material simulation method.The results showed that the roof of the fully-mechanized top coal caving mining face was a com bined suspended boom beam-articulated rock beam structure. And there were five basic movement forms existed in the combined suspended boom beam and they were a combined suspended boom beam-directly falling form,a combined suspended boom beam-articulated rock beam conversion form,a combined suspended boom beam-articu lated rock beam alternative form,a combined suspended boom beam-bridging-reverse rotation form and combined suspended boom beam-bridgingdirectly falling form.With the analysis on the five basic movement forms affected to the mine strata pressure law,the paper revealed that the main reasons of the unclear mine strata pressure in the fully-mechanized top coal caving mining face in the quite thin thick seam were the combined suspended boom beam-articulated rock beam alternative movement occurred i n the roof structure. The paper revealed that the combined suspended boom beam-articulated rock beam conversion form occurred in the roof structure of the fully-mechani zed top coal caving mining face in ultra thick seam and the combined suspended boom beam-bridging-reverse rotary or combined suspended boom beam-bridging-directly falling caused a small period roof weighing.The rotary of the articulated rock beam structure could cause the combined suspended boom beam to lose the stability and cau se a high periodical roof weighing and thus the movement form of the combined suspended boom beam structure mostly would be a direct falling form.