Experiment Of Coal Containing Gas Under The Condition Of Unloading Confining Pressure Research On Relief Scope Of Upper Protective Seammininig

In the underground coal mining activities， gas treatment is important，and thepermeability characteristic of coal containing gas is the principal and crucial problemin gas controling， only understanding permeability characteristics of coal containinggas，the gas drainage can be proceeded to solve or ease the dangerous of coal and gasoutburst，This paper applied“Thermo-fluid-solid coupling with triaxial servo-controlledseepage equipment of containing-gas coal”，researched the gas seepage characteristicsof raw coal in original stress field by simulating the stress field， mechanical and gasseepage characteristics is researched under different confining pressure、different initialaxial stress and different unloading speed of confining pressure，besides， by usingFLAC numerical simulation software，this paper researched the size and distribution ofstress field of liberated coal seam after the liberation coal seam is recovered， bycombinting the simulation and measured data，this paper analyzes the effect of releasingpressure.The main research results obtained as follows:①through loading and unloading the axial stress and confining pressure， gasseepage characteristics of soft coal under in-situ stress field is researched，the results ofthe study show that， in loading process， the relationship between permeabilityeffective stress tends to function relation，in unloading process， the relationshipbetween permeability effective stress tends to the power function relation， in addition，through repeated the loading and unloading， the experimental results show that after2~3times cycle， the strain changes very little， from permeability reaults， after theformer2~3times cycle， its permeability almost no change in another a loading andunloading cycle.②By using “Thermo-fluid-solid coupling with triaxial servo-controlled seepageequipment of containing-gas coal”，researched the main influence factors (axial stress，confining pressure and gas pressure)of raw coal permeability， and fitted the functionrelations.between permeability and the axial stress (confining pressure， the gaspressure)③By using “Thermo-fluid-solid coupling with triaxial servo-controlled seepageequipment of containing-gas coal”，proceeded experiment of unloading confiningpressure in the combination conditions of different confining pressure， different initial axial stress and different confining pressure unloading speed， obtained mechanicsproperties and gas seepage characteristics，in this experiment，first of all，axial stressand axial strain curve should be obtained in different confining pressure conditionsshould be obtained to get the yield stress of coal in different confining pressureconditions to establish the initial axial stress which is less than yield stress，byproceeding the tests of unloading confining pressure before yield stess，can get themechanics and gas seepage characteristics of coal containing gas under differentconfining pressure， different initial axial stress and different confining pressureunloading speed，then sums up the relationships between the time of axial stressplatform and confining pressure unloading speed or initial axial stress，obtain thechange rule of the permeability、strain、deformation modulus and poisson’s ratio in theprocess of unloading confining pressure，and fitted the function of permeability-time inthe form of polynomial.④Proceed the test of unloading confining pressure after the peak stress indifferent confining pressure，in the test，add the axial stress to the peak stress by thedisplacement loading method，turn to force control and maintain constant axial stressthen start to unloading the confining pressure after the peak stess，obtain the mechanicsand gas seepage characteristics of coal in the process of unloading confining pressureafter peak stress.⑤By using software ABAQUS numerical simulation， analyse the size and thedistribution rule of Stress field of liberated coal seam after the liberation layer is minedover. in addition， through the field test in206test field in baijiao coal mine of Sichuancoal industry group，combine the simulation results and the field observation results ofgas pressure、gas content and coal permeability in the process of mining liberationlayer，this paper analyse discharging pressure effect and determine the scope ofliberation.