Study on thermal damage characteristics of granite based on GBM modeling method of particle flow
[Objective]It is great significance to study the crack propagation law and damage characteristics of granite under ther-mal-mechanical coupling,and to reveal the influence of rock microstructure evolution on its mechanical behavior.[Methods]Based on the GBM modeling method of particle flow code,a thermal-mechanical coupling numerical model representing the heter-ogeneous microstructure of granite is established.The evolution law and mechanical behavior of micro-cracks in granite at 20 ℃ and treated under high temperatures(200 ℃,400 ℃,600 ℃ and 800 ℃)are studied.[Results]The numerical results show that the number of thermal-induced cracks increases significantly with the increase of heat treatment temperature,and the ther-mal-induced cracks in granite model are mainly tensile cracks at mineral grain boundaries.When the heat treatment temperature exceeds 400 ℃,a large number of intragranular tensile and shear cracks begin to initiate in quartz and feldspar minerals.[Conclusion]The initiation,propagation and coalescence of thermally induced cracks lead to the deterioration of mechanical properties of granite.With the increase of heat treatment temperature,the peak strength and elastic modulus of granite decrease,while the peak strain increases.When the temperature rises to 600 ℃,thermal-induced cracks begin to dominate the final failure mode of granite,and the post-peak stage of stress-strain curve change from brittleness to ductility.Due to the obvious increase of thermal-induced cracks with the increase of heat treatment temperature,granite produce more acoustic emission events in the ear-ly stage of uniaxial loading.In addition,axial stress causes stress redistribution in granite,and more stress-induced cracks are produced in stress concentration areas,which eventually leads to instability and failure.
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