Study On Non-Pillar Mining Roadway Support Technology Of Composite Roof In Shallow Coal Seam

Because the Nangliang Coal Mine adopts the coal pillar retaining roadway mining,it wastes a large amount of coal resources,so the non-pillar mining can reduce or even avoid the occurrence of the waste of coal resources.According to the geological conditions of the 30104 air-return roadway,shallow coal seam and composite roof.Combined with the stress and deformation characteristics of the roof in different regions,designing and optimizing the supporting scheme of the air-return roadway.This thesis uses method of field investigation,physical experiment,theoretical calculation and numerical simulation,conducts the study of stress distribution law of the composite roof and air-return roadway supporting parameters,the main research results are as follows:(1)Mechanical models of the traditional gob-side entry retaining and the gobside entry retaining by roof cutting is constructed.It is concluded that the support strength required by the gob-side entry retaining by roof cutting is less than that required by the traditional gob-side entry retaining,so the cost is lower and the economic feasibility is better.(2)Mechanical models of compound roof in the front of working face and behind the working face are constructed,and load capacity of each layer is calculated by using the theory of composite beam.Deformation and stress distribution of the different areas are analyzed.Under the action of the overburden strata,the roof is bent from the first layer and the bending deformation is the largest,following with the bending deformation of the first layer,the second layer of the roof also appears bending deformation sinking,and so on and layer by layer,with the rise of the height,bending deformation is getting smaller,after the broken of fifth layer,it reachs a stable state;The stresses of roof have different distributions in different roadway areas,with the increase of height,the maximum stresses value of each layer decrease gradually.The maximum values of bending deformation and stresses in the area behind the working face are larger than that in the area in the front of working face,and these are more obvious in the side of goaf,so the area behind the working face is the key area of gobside entry retaining.(3)According to the characteristics of 30104 air-return roadway,the preliminary supporting parameters are designed through the theoretical analysis of single prestressed anchor and group anchor cable,the support effect of roadway under different slit parameters and support parameters was simulated by UDEC,the supporting schemes of 30104 air-return roadway was designed and optimized.Finally,a set of optimal support scheme including optimal slit parameters,dynamic pressure reinforcement support and combined support of "bolt+ cable+ constant resistance cable" is established.(4)Mine pressure observation scheme is designed according to the actual production and geological conditions of 30104 air-return roadway.The stress on the constant resistance cable and the displacement of roadway surrounding rock are measured on site,which verify the rationality and validity of the selected supporting parameters.