Study on the effect of rock stratum structure on the stability of weakly cemented layered floor and the floor control measures: A case study of Meihuajing Mine

Given the deformation and instability of the layered floor of weakly cemented soft rock roadway, taking the mining roadway of Meihuajing Mine as the engineering background, the deformation and instability mechanism of the floor and the control measures of the surrounding rock under different stratum combination conditions are studied by using the methods of field investigation, numerical calculation and field test. The results show that: (1) the layered characteristics of surrounding rock in weakly cemented soft rock roadways are significant, and the combination structure of floor rock strata is complex and changeable. Under the influence of engineering disturbance, the roadway has a tendency of large deformation, especially floor heave. (2) The buckling instability of the layered floor is caused by the layered weakening effect, and the unstable zone, the substable zone and the stable zone are formed successively from the shallow to the deep. With the increase of the layer thickness, the integrity of the layered floor is improved, the layered weakening effect is reduced, and the overall stability of the layered floor is improved. (3) The existence of weak interlayer further degrades the integrity of layered floor, and the progressive failure of floor rock mass layer by layer is more significant under the influence of layered weakening effect. (4) The relatively hard rock stratum in the composite structure plays an important role in controlling the deformation and failure of the floor, playing the role of "local key stratum." (5) Based on the cooperative control countermeasure of roof-rib-floor surrounding rock, the support technology of roof and ribs supported by blots mesh beam cable + floor supported by bolts grouting hardening + full section shotcrete is proposed. The results of numerical calculation and field test show that the support scheme greatly improves the stability of layered floor.