The Study Of Creep Constitutive Equation Of The Coal-rock Body And Its Stability

With mining depth increasing continuously in our country, Geological conditions ofunderground mining become more complicated. Then, destabilization problem of coal-rockbody are increasingly emerging. Due to the influence of coal-rock body creep features in thedeep mine, the accident caused by delayed destabilization of the coal-rock body and delayedoutburst coal and gas occur frequently. Delay and concealment of these accidents harm thesafety of coal mine greatly. Therefore, the study of creep constitutive equation and mechanismof delay destabilization of the coal-rock body for coal mine safety is of important theoreticaland practical significance.Based on theoretical analysis, laboratory test and numerical method, the paper studied oncreep constitutive equation of the coal-rock body, and analyzed stability of the established coalpillar in roadway and the coal-rock body in high thickness gas mines.In order to study creep constitutive equation of the coal-rock body, this paper combinedwith visco-plastic unified constitutive model and the mechanical characteristics of coal androck. Then, we introduced a softening and a hardening function for a new nonlinearrheological model with time-varying parameters (PTM model). From the angel of energy, wepresented the delayed destabilization condition of PTM model by using the principle ofminimum potential energy. Meanwhile, based on the results of uniaxial compression creep test,we realized that TPM model can reflect the true creep process of the coal-rock body bycalculating parameters of PTM model. According to the delayed destabilization condition, wecalculated the delay unstable time period of coal pillar, which was established for retainingroadways. The result shows the energy analysis method of stability analysis has a guidingsignificance for engineering practice.In addition, based on the principle of effective stress factors and the damage caused by flow and pressure of the gas, we putted forward the TPM model of the coal-rock body in highthickness gas mines. Using the principle of minimum potential energy, we also analysis delaydestabilization process of coal-rock body on the heading face. The result shows that thedecreasing of destabilization criterion U changes faster when the initial gas pressure P is lager.That is, destruction speed of the coal-rock body will faster.