不同温度下粉砂岩力学性能宏细观劣化机制研究OA

This study investigates the degradation effect of high temperature during underground coal gasification on coal seam roof rock.Using a specific heat capacity measuring instrument,XTDIC three-dimensional full-field strain measurement system and scanning electron microscope(SEM),six groups of rock specimens were treated separately for uniaxial compression tests.Results show that 400℃is the critical threshold for the transition of mechanical properties of specimens:At 25℃,200℃and 400℃,increasing temperature led to decreasing porosity,more tightly packed mineral particles,post-poned occurrence of deformation localization,decreasing value of maximum displacement dislocation e-volution and more intense ejection failure;At 600℃,800℃and 1 000℃,specimens exhibited ag-gravated internal damage,significantly increasing porosity,degrading mechanical properties,earlier occurrence of deformation localization and intensified spalling failure.With rising temperature,their u-niaxial compressive strength,elastic modulus and thermal conductivity showed initial increase and sub-sequent decrease.The transformation process of the failure mode is accompanied by varying degrees of ejection-spalling damage.This study reveals the degradation patterns and threshold of siltstone under different temperatures during underground coal gasification,and its macro-meso damage evolution mechanism,providing a theoretical basis for roof stability evaluation and prevetion of engineering disas-ter in high-temperature surrounding rock during gasification.