Study on the multi-span statically indeterminate structure of roof in solid filling mining and the controlling effect of backfilling hydraulic supports

The purpose of this paper is to solve the problem of determining the key parameters of filling mining under different geological and mining conditions. Based on multi-span statically indeterminate structure,the ‘ roof-support- filling body’ interaction mechanics model with basic roof was established under the condition of actual deformation form of filling mining strata movement. In this model,the coal wall and filling body are main supporting bodies,while filling supports define the deformation of the basic roof. According to this model,the mechanical equilibrium equation and deformation coordination equation of the continuous roof was established to solve the problem when the pressure of the filling supports is unknown,which changed the simplified analysis method of thinking of the roof pressure as a uni- form load in the previous mechanical models. The elastic foundation of the filling body was dispersed into a number of equivalent elastic supports,and the single-span isolator was analyzed to establish the section deformation equation. Then the matrix expression of section deformation equations was obtained,which contained n+2 deformation equations and formed n+5 solving equations with three equilibrium equations,corresponding to n+5 unknown constraints. In or- der to reflect the distribution of roof load more accurately and analyze relationship of roof,supports and filling body more reasonably,this paper attempted to combine the mechanical model with the numerical model to solve this prob- lem. Then a numerical model with same parameters of the filling supports and filling body in above mechanical model was established. The stress curve calculated by the numerical model was used as the roof pressure q(x) and substitu- ted into the ‘roof-support-filling body’ interaction mechanics model. Therefore all the support reactions,internal force and moment of beam in the model could be solved,and the mutual interaction relationship between the roof,the sup- ports and the filling body was obtained. The variation law of the support strength of the front and back canopy of hy- draulic supports with double canopy structure under condition of different elastic foundation coefficient of filling body and different roof deformations was analyzed by a specific calculation example,providing an effective method for the determination of key parameters of filling mining.