Study of Falling Roof Vibrations in a Production Face at Roof Support Resistance in the Form of Concentrated Force

One of the main reasons of roof support failures in production faces is mismatch of their parameters and parameters of dynamic impact on the metal structure from the falling roof during its secondary convergences. To assess the parameters of vibrational interaction of roof support with the roof, it was suggested to use computational models of forces application and a partial differential equation of fourth order describing this process, its numerical solution allowed to assess frequency, amplitude and speed of roof strata movement depending on physical and mechanical properties of the roof strata as well as on load bearing and geometry parameters of the roof support. To simplify solving of the differential equation, roof support response was taken as the concentrated force

Results of the modal analysis of the underground mine hydraulic leg in various modes of its operation

The article describes the construction of models and the initial conditions for the various modes of legs operation. The article presents the way of setting the initial conditions for the initial thrust with constant pressure and for leg operation in the mode of increased pressure caused by the lowering of the roof. The results of modal analyses conducted for 2 modes of leg operation are shown. It is shown that the form and frequency of natural oscillations of hydraulic legs are determined by their design, pressures of the initial thrust and nominal operating resistance, as well as by the operating modes which differ in schemes of interaction of leg elements with interacting elements of the support and the roof and floor strata. At the same time, changing the operating mode of the legs changes the natural frequency both to the higher and to the lower side, as well as the form of oscillations of certain frequencies. For more accurate calculation of the frequency response of hydraulic legs to the external load of frequencies, it is proposed to take into account not only their design and power properties, but also the modes of their loading