Prediction model for increasing resistance of hydraulic support due to slow motion of the roof in mechanized mining working face

The support crushing disaster easily occurs due to the roof slow motion of fully mechanized caving face during the maintenance and halting production.It is a key issue to predict the evolution of the hydraulic support work resistance and overburden for the prevention and control of the support crushing disaster.The top coal,the immediate roof and the basic roof above the support of a fully mechanized top coal caving face were considered as overall macro roof.The generalized Kelvin model was employed to predict the slow motion of the macroscopic roof and the support working resistance evolution due to the slow motion in mechanized mining working face,and the increasing resistance predicting model due to the slow motion of the macroscopic roof was established.The hydraulic support working resistance evolution at the 303 fullymechanized work face in Cuimu coal mine was predicted using the model proposed in this paper.The effects of the initial supporting force and the mechanical properties of macro roof on the slow motion and support working resistance evolution were investigated,and the results show that:① the increasing resistance evolution of hydraulic support during maintenance and halting production of working face can be well predicted by the predicting model in this paper.② The parameter of E2 in the predicting model presented in this paper is used to describe whether macro roof is soft or hard.The larger E2 is,the harder the macro roof is,and the smaller the subsidence of the macro roof and the resistance of the support after initial support is.③ With the initial support force increase,the E2 of the macro roof increases linearly,however the increasing resistance decreases approximately linearly.Increasing the initial support force can improve the integrity of the macro roof and reduce the increasing resistance due to the slow motion of macro roof.④ The viscosity coefficient,η,mainly influences the shape of the working resistance evolution curve with time.The larger ηis,the slower the evolution curve converges.⑤ Combining the mean calculation parameters of many supports (or cycles) and t the increasing resistance predicting model of the macroscopic roof in in this paper,the evolution behavior of working resistance of support in working face can be predicted.