Study on deformation characteristics and deformation mechanism of steep coal rock interbedded roadway

In view of the deformation problem of steeply inclined coal-rock interbedded roadway, the field measurement and numerical simulation experiment methods were adopted, and the surrounding rock stability joint monitoring equipment was used to analyze the distribution characteristics of surrounding rock cracks, the change of bolt tension, the deformation of roadway and its stress distribution law in steep coal-rock interbedded roadway. The results show that the average horizontal principal stress of the B8 steeply inclined coal-rock interbed roadway is 24.3 MPa, which is about 3.08 times of the vertical in-situ stress. When the rock layer transitions to the coal seam, the hole wall is relatively broken, and the hole wall gradually produces shear dislocation with the increase of the drilling depth. The steeply inclined coal-rock interbedded roadway has the characteristic of asymmetric deformation, and the heave of the south is 0.60-1.00 m, which is larger than that of the north. The changes of the two sides show a phased trend of "convergence period- nearly stable period-stable period". The "convergence period" of the roadway has the creep characteristic of about 5 days, and the daily deformation is 0.10-0.20 m. Therefore, the construction operation should avoid the convergence period of about 5 days in the roadway. The deformation of the roadway in the repairing stage caused damage to the bolts, causing the bolts to be pulled out when the anchoring force of the south side bolt was 30 kN. After the roadway deformation was stable and relatively stable, 15 of the 90 bolts had low quality bolts, accounting for 30 kN, which reached up to 16.67%. Due to the influence of geological factors in the steeply inclined coal stratum, the vertical cracks of the surrounding rock of the roadway are relatively developed. Under the action of horizontal stress, the weak interlayer is prone to dislocation and deformation between structural planes. The layer separation deformation of the rock stratum occurs, which eventually leads to the large deformation of the roadway.. The two ribs present the characteristics of asymmetrical deformation of the roadway floor heave that is high in the south and low in the north. After the deformation and instability of the south side, the rock strata of the north side of the roadway is subjected to greater overburden and stronger stress concentration effect. The research results provide a scientific basis for the deformation control of the steeply inclined coal-rock interbedded roadway.