Softening effect and crack evolution law of fine sandstone with different water contents
In order to study the mechanical properties and crack evolution law of deep hard roof after immersion,taking the-810 m fine sandstone in Pansan mining area as the research object,the experimental study on the mechanical properties of uniaxial compression with different water contents was carried out.The sensitivity of softening effect and brittleness coefficient were analyzed,and the crack evolution law of fine sandstone with different water contents was revealed.The results show that the water content of fine sandstone is negatively correlated with its brittleness coefficient.The increase of water content re-duces its peak stress,peak strain and elastic modulus,and weakens the macroscopic damage degree of rock.Under the contin-uous action of external load,the increase of water content is the key factor to induce the occurrence of pore water reaction force in advance,and it will promote the growth of horizontal strain on the surface of fine sandstone.There is a potential rela-tionship between the maximum horizontal strain on the surface of fine sandstone and its crack development,and the macro-scopic cracks on the surface appear in the maximum horizontal strain area.The research results can provide some reference for the softening mechanism research of hard roof water injection.
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