Experimental Research On Anti-collapse Support Device For Borehole Mining In Soft Coal Seam

In high-gas low-permeability soft coal seams,due to the strength of the coal body is smaller than that of the rock body,most of the coal gas drainage holes are air or hydraulic slag discharge,the support force in the hole is very small,and in the ground stress,coal seam gas pressure and coal Under the influence of body strength and other factors,the gas dr ainage hole drill in soft coal seam is prone to deformation or even collapse.Not only does it affect the normal progress of gas drainage,it will even cause a gap in the gas drainage of the coal seam,causing a potential threat of coal and gas outburst.In order to effectively solve the negative impact of borehole deformation or collapse on gas extraction,the gas extraction efficiency of high gas soft coal seam is improved to a certain extent.In this thesis,through theoretical analysis,numerical calculations,laboratory performance experiments and field tests,the performance and effect of the anti-collapse support device for the drilling and drilling of soft coal seams are studied.The main research content and research results of the paper are as follows:(1)According to the actual needs of the drilling support site,complete the design of the special-shaped grouting bag support.Choose materials with flame retardant,water-permeable and impermeable properties as the selection materials for the production of special-shaped grouting bag stents,add a certain proportion of quick-setting agent,early-strength agent,expansive agent,etc.to the cement to make grouting to meet the needs of field tests Slurry.(2)Using RFPA numerical simulation software,different models were established to complete the numerical calculation according to the presence or absence of supports in the borehole and the spacing of the supports.The appropriate support spacing is determined to provide a theoretical basis for subsequent field industrial tests.(3)The support strength of the heterosexual grouting bracket is closely related to the size of the grouting chamber.The size of the shaped connector determines the parameters of the grouting chamber and indirectly determines the mechanical properties of the stent.Special-shaped grouting bag stents with different sizes of chambers were prepared.An integrated platform for testing mechanical properties was used to study the changes in the limit stress and gas flow area of different stents with the size of the plastic connecting parts to determine the optimal stent design size.(4)Use the special-shaped grouting bag holder to carry out on-site industrial tests to study the gas mixing and concentration change rules of supported and unsupported boreholes.Analyze and summarize the protective effect of special-shaped grouting bladder on the collapse of drilling holes.In this paper,with the background of anti-collapse of gas drainage borehole,a special-shaped grouting bag support is designed.The research results improve the gas drainage effect of easily collapsed borehole and have certain guiding significance for the design and improvement of gas drainage engineering.