Anchor prestress field distribution characteristics and support optimization of multi type composite roof

In view of the diversity and complexity of the roof structure of the coal mine roadway, roof structure type is divided, through the in-situ strength test of large-scale roof and the peep of surrounding rock structure.The paper analyzes distribution characteristics of prestress field of anchor with different roof types and anchoring parameters and optimized anchorage parameters of compound roof roadway.The results show that the roof types of main coal seam roadway in Yangquan mining area of Jinneng Group can be divided into soft roof, soft hard alternate type, bottom hard upper soft type and hard soft alternate type.The distribution characteristics of anchor prestress is “two tension and one compression” as a whole, no matter in single or compound rock stratum.In the composite rock stratum, the bedding surface is the main factor that hinders the stress transfer of bolt support, and the more the bedding surfaces are, the smaller the effective compressive stress range is.By applying high preload and using large surface protection components, the range of bolt compressive stress area can be effectively expanded.In addition, by adjusting the anchor length or anchor length, the bedding surface is located in the area with high compressive stress, which can effectively avoid vertical separation and horizontal dislocation of the roadway roof.Taking the soft roof roadway as an example, the field practice of surrounding rock anchorage support optimization of composite roof roadway is carried out to verify the feasibility of theoretical research.