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Aimed at the stability of surrounding rock in Pingdingshan Coal Mine, took a typical deep roadway with joint fissured surrounding rock as study object, used discrete element numerical simulation, simulated the deformation and failure mechanism of surrounding rock, and the control technologies of joint fissured surrounding rock roadway were proposed. The results show that the tensile failure appears at vault and two side-walls and in the middle of floor at first. Then, the shear failure appears at spandrel and two base angles. The failure zone extends into the deep area until the roadway is instable. According to the in-situ monitor data, it is concluded that the stress in anchor and cable tends to be stable after supporting for two months, as well as the horizontal convergence, vault subsidence and floor heave. It means that the supporting technology works and the stability of soft surrounding rock in deep rock roadway is controlled. [ABSTRACT FROM AUTHOR]

In order to study the creep property of salt rock, triaxial compression creep tests with step loading axial stress to salt rock specimens were carried out on the RLW-2000 rock rheology testing machine. The test results show that the instantaneous strain, creep strain and creep velocity of salt rock increase gradually with the increasing of axial stress, meanwhile, the duration of the primary creep stage gradually extend. And isochronous stress-strain curves of salt rock indicate that the creep process of salt rock has nonlinear characteristic, and the nonlinear degree is related to creep time and stress level. Based on nonlinear rheological theory, a new nonlinear viscosity component with a variable viscosity coefficient was proposed, and the viscosity coefficient of which was time and stress-dependent. Then, by using this proposed nonlinear component to replace the conventional viscous components in Burgers model, a nonlinear vis-coelasticity creep model, which was named MBurgers model and can describe the nonlinear creep property of salt rock was established. According to triaxial compression creep test results of salt rock, the parameters of MBurgers model were in versed by using curve fitting method. And the theoretical curves accord well with the test curves, which indicates that the MBurgers model can describe the creep property of salt rock. [ABSTRACT FROM AUTHOR]

An updated approach to refining core indicators of pulverized coal used for blast furnace injection based on principal component analysis was proposed in view of the disadvantages of the existing performance indicator system of pulverized coal used in blast furnace. All the performance indicators of pulverized coal injection were taken into account in this presented method, including calorific value, igniting point, combustibility, reactivity, flowability, grindability, etc. Thereafter,the four core indicators of pulverized coal injection were selected and studied by using principal component analysis, namely, comprehensive combustibility P1, comprehensive reactivity P2 comprehensive flowability P3, and comprehensive grindability P4. The newly established core index system was not only beneficial to narrow down current evaluation indices but also effective to avoid previous overlapping problem among indicators by mutually independent index design. Based on overall 4 characteristic indexes, the injection characteristics evaluation index P was further introduced, and combined with fundamental characteristics evaluation index F, the final evaluation of pulverized coal performances was obtained. [ABSTRACT FROM AUTHOR]

In order to study the distribution of dust particle matter (including PM2.5) in coal workface, the concentration of total dust, PM10 dust and PM2.5 dust were measured with the dust concentration tester during the mining process in all roadways of Coalface 91324 that is the comprehensive mechanized coal face at a coal mine in Jincheng city. The results were analyzed and show that the total dust concentration is at its maximum 5 m downwind of the coal cutter while PM10 and PM2.5 dust fluctuates heavily in the coalface; the concentrations of three kinds of dust (the total dust, PM10 dust and PM2.5 dust) increase gradually and reach their maximum values at 330 m, then decrease slowly in the auxiliary return roadway. The concentration of these three kinds of dust fluctuates within the low concentration range in the main return roadway. In the main return roadway and auxiliary roadway the maximum levels of PM2.5 dust are 56.087 mg/m³ and 180.39 mg/m³ respectively. The PM2.5 dust is above the limit of ambient air quality. These findings provide the parameters for modifying the standard of dust testing and prevention. [ABSTRACT FROM AUTHOR]

After careful analysis of the regularity of ground surface subsidence in mined-out region and the characteristics of MMF curve model, a new time function model based on MMF model was proposed in consideration of the shortage of current ground surface subsidence predication models. Then the rationality of the new model was verified through project cases. The result indicates that the new model can give a good reflection of the regularity of ground surface subsidence in mined-out region and can accurately predicate surface subsidence. The predication values of the new model is a little greater than measured values on condition of proper measured data quantity, which is safe in the engineering. [ABSTRACT FROM AUTHOR]