Study On Layer Rule Of Compound Roof In Deep Mining

With the mining depth increasing,safety accident caused by roof collapse due to separation of composite roof is becoming one of the main disasters in coal mine. Analyzing the separation mechanism and its influenceing factors is the key to prevent and control roof separation and safety accidents, which provides the basis for distinguishing the interlayer separation stability and determining the standard interlayer separation stability reasonably. Based on determining the numerical model for complex roof separation analysis of deep mining, mechanism of bed separation and influenceing factors are analyzed. It shows that interlayer separation changes with time. According to the numerical simulation.Combined with the theoretical analysis, interlayer separation methods of the practical engineering detection is determined,the conclusions are drawn:(1) The stress analysis of mining complex roof constructural face in different conditions of deep minging is shown that the mid of constructural face is separated by normal tensile stress and the separation of both ends of structural face is caused by shear stress.(2) The scope of the separation of structural face can be used as a standard to determine separation stability, the range of action of normal tensile stress can be obtained by numerical simulation.(3) The separation of the middle of the structural face is not much correlated to separation stability; the size of interlayer separation in the scope of the separation of structural face tends to be well-distributed. When the value of a structured surface abscission layer is used as the criterion of stability, the practical measured value of the two ends of the roadway should be compared with the critical value.(4) The rock stress,rock characteristics and rock thickness have obvious influences on interlayer separation, the rock mechanical properties had little effect on the separation stability.(5) There is an original critical rock stress, when the rock stress is near the critical value, the scope of interlayer separation increases significantly.(6) As the rock characteristics are weaken, the scope of interlayer separation is increased, when the rock weakened to a certain extent, it increases significantly.(7) With the rock thickness increase, the value of interlayer separation and the scope of interlayer separation reduce and the separation instability increase, it is not rational to use the value of interlayer separation to discriminant the stability of complex roof.(8) With time varying, the different features are shown between interlayer separation and plastic deformation, the interlayer separation of complex roof in deep coal tunnel is shown as plastic deformation in the initial stage, but it is shown as interlayer separation in later stage. According to this characteristic, the interlayer separation can be separated from the total separation.(9) The numerical simulation can be used to analyze the law that interlayer separation changes with time and provide the base of the separation stability which can be discriminated by the speed attenuation coefficient of interlayer separation.(10) The size of plastic deformation can be estimated by regression analysis of time-varying in the early (0-25d) of the complex roof separation and the value of interlayer separation can be determined by minus between total separation value and plastic deformation.