Experimental Study On Sandstone Instability And Friction Induced Goaf Gas

Sandstone roofs and gas are widely present in coal mines in China.The mechanism of the gas explosion caused by the frictional effect caused by the instability of the sandstone roof is not completely clear.Only after such related accidents can enough attention be paid to cause Gas control work blind spot.Therefore,it is important to study the friction effect caused by the instability of the sandstone roof and the factors affecting the gas explosion in the goaf,clarify the accident occurrence mechanism,avoid such accidents,and ensure the safety of coal mine production and the safety of personal property.In this paper,based on the masonry beam structure,the mechanical analysis of the overlying rock layer is carried out to clarify the conditions of the roof rock layer falling and instability.The roof rock layer forms different effective energies during the sliding failure process,mainly including the wind energy,sound energy and Thermal energy,based on the theory of "masonry beam",rock mass mechanics and thermodynamics,clarifies the energy convcrsion during the process of rock instability.Taking three kinds of sandstones with different quartz content as the research object,we designed the test device and test plan by ourselves,compared the relative friction velocity,gas concentration,and friction combination form between sandstones to the ignition of gas by the friction effect,and recorded the sparks generated under the friction effect,Fire bouquet,gas ignition and gas explosion four test phenomena,the analysis of the impact of three different factors on the sandstone friction effect of gas ignition,get the spark,fire bouquet,gas ignition and gas explosion test phenomena above The difficulty of occurrence under the three variables is directly related to lithology.The above four test phenomena have a negative correlation with the relative friction speed between sandstones,that is,the greater the relative friction speed,the shorter the time for the four test phenomena to appear.The appearance time of sparks and fire bouquets has nothing to do with the gas concentration in the test chamber.The occurrence time of gas ignition and gas explosion has a negative correlation with the gas concentration in the test chamber.That is,the greater the gas concentration,the shorter the time for the two test phenomena.X-ray diffractometer was used to analyze the three sandstone components.Testo890-2 thermal imager was used to record the temperature field changes under different friction speeds and different friction combinations.The impact of quartz content on the maximum flash temperature under the friction effect was analyzed.It is concluded that when the same type of sandstone rubs against each other,the highest flash temperature value produced by the sandstone friction effect is positively correlated with the quartz content.The relationship between the maximum flash temperature value and the relative friction velocity between sandstones is analyzed,and it is concluded that the maximum flash temperature value and the relative friction velocity are positively correlated.When different sandstone combinations friction,only for the three sandstone patterns in this test,when the quartz content ratio is close to 3:1,the maximum flash temperature value is the largest.It is clear that the temperature generated under the friction effect of sandstone is changed by means of heat transfer,and the friction heat surface formed after the sandstones rub against each other is the main ignition source.