Mechanical characteristics and support mechanism of coal-rock combined body under unload-loading conditions beyond peak strength
To further investigate the mechanical properties of coal-rock combined bodies under post-peak unload-loading conditions,simulation tests were conducted using PFC(Particle Flow Code)nu-merical simulation software.The study analyzed the strength,elastic modulus,peak axial strain,bursting energy index,and acoustic emission characteristics of coal-rock combined bodies under different levels of post-peak unloading stress,unloading rates,and support schemes.The results indicated that the damage occurred in coal-rock combined bodies during the post-peak phase,resulting in lower strength,elastic modulus,bursting energy index,and maximum AE counts compared to pre-peak conventional u-niaxial compression.Higher post-peak unloading stress levels led to increased post-peak unload-loading strength of coal-rock combined bodies,under the same unloading rate.The unloading rate had two effects on the post-peak unload-loading strength:an overall strengthening effect and a local weakening effect.Consequently,under the same post-peak unloading stress level,the post-peak unload-loading strength of coal-rock combined bodies exhibited a"first increasing,then decreasing"trend with increas-ing unloading rate.Support systems significantly enhanced the strength and elastic modulus of broken coal-rock combined bodies.However,only stable support effectively reduced the bursting energy index.Therefore,to improve the stability of broken coal-rock masses and mitigate the bursting risk,it was cru-cial to select support systems with high strength,high reliability,and ample deformation capacity,while also increasing the support surface area.The practical application of these research finding in an engi-neering example demonstrated their guiding significance for in-situ engineering practice.
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维普
