Experimental study on creep characteristics of infiltrated coal-rock under load

DOI: https://doi.org/10.21203/rs.3.rs-661339/v1


For the water-rich zone in the coal tunnel rock body perennial suffer from water infiltration destabilization destruction problem.In this paper, the influence of stress level and infiltration time on the creep properties of coal-rock was systematically studied after the water infiltration test, scanning electron microscope(SEM), water content test, uniaxial compressive strength test and creep mechanical properties test.The whole process of coal-rock creep is described by Hooke's body, Kelvin body and damage elastic-plastic body, and the total damage variable was introduced to show the weakening effect of the coupling effect of stress and water infiltration on the creep properties of coal-rock.A creep constitutive model of coal rock damage considering the weakening effect of water infiltration was established, besides, the influence law of stress level and infiltration time on creep parameters of coal rock was analyzed.The study shows that coal rocks underwent a process from surface drying and shrinkage to water absorption and swelling to water-filled infiltration damage in the infiltration test.With the increase of infiltration time, the water content of coal-rock tended to increase and eventually stabilizes, while the uniaxial compressive strength gradually decreased.With the increase of stress level and infiltration time, the stable creep strain of coal-rock kept increasing which accelerated creep advance, and its internal damage continued to accumulate and eventually led to destabilization damage.At the same stress level, the creep parameter E0 showed a tendency to increase and then decreased with the increase of infiltration time, while E1, η1, tF, E2 and ν continued to decrease.Combined with the microstructural changes of coal rocks in the water infiltration process, the change law of mechanical properties of infiltrated coal-rock and the intrinsic softening mechanism were revealed.Comparing the theoretical model of infiltrated coal rock creep with the experimental data, the model developed in this paper reflected the whole process of infiltrated coal-rock creep deformation and damage, and can characterize the influence of infiltration time and stress level on coal-rock creep properties, which verified the reasonableness of the model.

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