Experimental study on the movement law of roof in pitching oblique mining area of steeply dipping seam

In order to study the movement of the roof and its interaction with the support in pitching oblique mining ar- ea of steeply dipping seam,the large-scale three-dimensional physical similarity simulation experiment and numerical simulation are combined to analyze the stress evolution,deformation and failure law of the roof,the filling characteris- tics of the caving roof and its interaction with the support in pitching oblique mining area. The results indicate that the pressure distribution and displacement of the roof show an asymmetric characteristic. Also,it has an “O-X” asymmet- ric breaking feature,and obvious timing characteristics,in which the order of “O” breaking is:the boundary of the goaf direction-the boundary of the mining face direction-the upper boundary-the lower boundary. The order of “X” breaking is:the upper main roof of the working face is destroyed first,and then the main roof is broken in a clockwise direction. The periodic weighting and the caving of the roof have the zoned characteristic and timing characteristic. The falling position at each area of the roof along the strike of the working face is relatively different from the position of support. The support in the inclined middle part of the working face is directly affected by the falling roof. The specific perform- ance is shocking-pressing-pushing,while tilting the upper and lower falling roofs only produces a downward thrust to the bracket during the descent process,and no obvious shocking and pressing phenomenon occurs. The upper part is the weakest,and the broken roof causes the varying degrees of “twisting-hybridization” to supports. The filling process of the caving roof to the goaf can be divided into four stages. The process of alternating transformation of each stage has an effect on the stability of the support in the middle and lower parts of the working face. The gangue filling area finally forms a stable filling area and a dynamic migration area along the strike. The study provides a scientific basis for the ground control in pitching oblique mining area of steeply dipping seam,and also enriches the ground control theory of steeply dipping seam.