The Research And Application On Strength And Creep Characters Of Cemented Body Used In Backfilling Mining

The mine environment and buildings’ safety were seriously influenced by the subsidencedisaster result from mining. So the control of the mining subsidence was very important to thecoal mining. The backfilling mining with paste was widely used in the coal mining as a kind ofgreen and scientific mining method. Contrasted to other backfilling materials the paste’s stiffnesswas larger and its effect for decreasing subsidence was better. But the researches on the pastecemented body’s creep properties were scarce while the researches were focused on itselastoplasticity characteristics. In this paper, the paste cemented body’s strength was studiedfirstly. Then its triaxial creep properties were researched and the scientific creep constitutiveequation on the early strength was constructed.The early strength’s influence factors, strength and deformation features of the pastecemented body were analyzed on the bases of multigroup uniaxial compression tests. Based onthe paste cemented body’s uniaxial compression strength its triaxial creep tests with differentstresses level were done and its creep damage constitutive model was derived and its long-termmechanical parameters were obtained. Then the laws of backfilling mining with paste underhighway and slope were analyzed after their numerical simulation. At the same time the mock-uptest on the backfilling mining with paste under highway was carried out and the well effect forthe control of subsidence was confirmed.The research results and conclusions were as follows:(1) The early strength of the paste cemented body would be larger when the early strengthagent or the binding material was more but it would be smaller when the water-binder ratio waslarger. The paste cemented body in the mock-up test was equipped with larger early strength andlong-term strength and could resist the overburden load and had larger modulus of elasticity.(2) The paste cemented body had obvious rheological behaviors. It had attenuation creepand steady creep when the stress was small. But the accelerated creep phenomenon would occurwith its strain was larger and larger when its stress continued increasing.(3) The damage evolution equation where the time and stress were considered was derived.The damage variable was taken into account in the modified visco-elastic plastic model whichincluded a nonlinear adhesive pot which was triggered by series connection strain. Then the creep damage constitutive model was established. And the creep law of the paste cemented bodywas explained well through the creep damage constitutive model.(4) The backfilling mining under highway and slope with the paste material in the mock-uptest could satisfy the control for the subsidence. The subsidence value of the highway would belarger when the backfilling height was larger but would be smaller when the paste cementedbody’s modulus of elasticity or the coal bed pitch or the mining depth was larger. The slope’ssecurity coefficient was1.28when the backfilling mining with the paste was used. So the slopewas safe.