Mechanical Properties and Energy Evolution of Saturated Limestone Under Cyclic Load
In order to study the mechanical properties and deformation laws of limestone in coal seam floor under hydraulic coupling and to prevent the instability and failure of coal floor caused by engineering disturbance,the conventional triaxial compression test and cyclic loading and unloading test of saturated limestone under different confining pressures were carried out based on rock microcomputer servo multi-field coupling system.The stages of total stress-strain curve of rock were divided by classical rock mechanics theory.The failure mechanism of rock under cyclic load was studied from the view of energy dissipation and cumulative damage.The study findings are as follows.Firstly,under the condition of constant confining pressure,the peak strength of rock sample under cyclic loading and unloading test is lower than that of conventional triaxial compression test,and the overall strain variable increases with the increase of unloading level,and the dilatancy phenomenon is gradually significant.Secondly,under confining pressure and cyclic load,shear failure is the main failure mode of saturated limestone.When confining pressure increases,transverse and longitudinal tensile failure occurs gradually.Thirdly,with the increase of cycle level,the proportion of elastic strain energy decreases correspondingly,and the proportion of dissipated energy increases gradually.Under the same cycle level,with the increase of cycle number,the dissipated energy shows a slight decrease trend.Finally,with the increase of unloading level,the rock damage behavior becomes more active,but there is a slight decrease in rock damage within the same cycle level,which is basically consistent with the evolution law and mechanism of dissipated energy.
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