Experimental Study On Similar Simulation Of Temperature Field And Stress Field Evolution Process In Coalfield Fire

At present,the management of coalfield fire has become a hot research problem both at home and abroad and a major problem to be solved urgently.It is of great significance to study the formation and evolution of coal field fire and realize the qualitative description of non-controlled combustion characteristics of coal field to the quantitative expression.In this paper,experiment method were conducted to study the mechanical properties of coal and rock mass in the fire zone under the thermal-mechanical coupling,determine the similar material and its ratio applicable to the temperature field and stress field evolution of coal field fire,through the similar simulation test,the evolution process of the temperature field and stress field of coal field fire is analyzed,Main contents are as follows:Based on the MTS880 electro-hydraulic servo material test system,the physical and mechanical characteristics of the coal and rock mass from the Huo Jitu fire zone under thermal-mechanical coupling are experimentally analyzed.When the temperature rises from room temperature to 400 ?,the peak value of rock sample increases from 60.04MPa to 77.36MPa,the increase is 28.85%;Between 25 ? and 400 ?,the peak strain of rock samples increased from 0.762 × 10-2 to 1.458 × 10-2,an increase of 91.3%;The elastic modulus of the rock mass increased from 4.86 GPa to 7.72 GPa and increased by 58.8%at the temperature increasing from 25 ? to 400 ?;The peak stress of coal sample increases first and then decreases with temperature,when the coal sample temperature reaches 200 ?,the peak stress increases with the temperature again,when the temperature increases,and gradually reduced.The comparative analysis of different materials was carried out from different angles,and the similar materials were applied to the temperature field and stress field evolution of coal field fire by orthogonal experiment.The effect of iron powder on the thermal conductivity of the sample is most significant.The amount of iron powder in the similar material can be adjusted to make the model similar to the prototype.The quartz sand is the aggregate and the gypsum and the white powder are used as the cement.Based on the self-constructed coal field fire temperature field and stress field evolution similar test platform:The high temperature region of the coal seam is located above the heating source.The temperature field of the coal seam has experienced the change process of the normal temperature zone,the warming zone,the high temperature zone and the cooling zone.The high temperature region of the overlying strata is located at the center of the rock model,and the temperature change is similar to that of the coal seam.The high stress region in the model is mainly located near the combustion zone,and the high stress region is advanced with the propulsion of the combustion,but the variation law of the stress is not exactly the same as the temperature change.Under the combined action of the temperature field and the stress field,micro rupture are formed in the overlying strata.As the combustion continues,these micro fractures will gradually expand,resulting in shear fracture and finally collapse.