Double period dynamic mechanism of support and sur-rounding rock in fully mechanized mining face

In order to reveal the dynamic mechanism of shield and surrounding rock in a fully mechanized mining face, the mining process was divided into several roof active cycles and the every roof active cycle was divided into several mining cycles. The double period dynamic mechanism of support and surrounding rock was put forward,based on the bond-beam structure mechanical model,elastic base beam theory and Newton’s second law. During the roof active cy- cle,the results showed that the state of the block A in the bond-beam structure model touching the gangue was the key node to judge the variation trend of the final resistance. The resistance increased before the key block A touching the gangue,and reduced after touching. In the mining cycle,the study showed that the structure of bond-beam was mainly sustained by bases which have the different elastic modulus and composed of coal wall,hydraulic support and goaf. Ac- cording to the different increasing characteristics of the resistance,the interaction process of support and surrounding rock in mining cycle was divided into a given load stage and a given deformation stage,and the resistance function of dynamic increasing was put forward. The increasing curve in the given load stage followed an exponential function,and the curve in the given deformation stage followed a logarithmic function. The fitting results of the data measured in workface with the Sihe Mine and Xinyuan Mine,indicated that the field measurement was consistent with the theoreti- cal analysis. The above research would provide a theoretical basis for roof disaster prediction and strata control.