Research on dynamic mechanical properties of rock mass with orthogonal intersecting cracks under two-dimensional static loading
In order to study the influence of confining pressure on the strength characteristics and failure characteristics of rock mass with cross cracks,considering the influence of crack penetration ratio,initial static load and strain rate,a biaxial dynamic and static combined loading test was carried out by using the biaxial Hopkinson pressure bar(BHPB)test system.The deformation process of the sample was analyzed with the help of digital image correlation(DIC)technology,and the strength characteristics,energy dissipation and fracture properties of cross-jointed rock mass were studied.The research results show that the dynamic strength and peak strain in the direction of the maximum principal stress decrease with the increase of the maximum principal stress or stress difference,but increase with the increase of the intermediate principal stress or strain rate,while the dynamic stress and peak strain in the direction of the intermediate principal stress show the opposite trend.With the increase of the differential stress,the energy loss per unit volume increases.With the increase of the crack penetration ratio,the dynamic strength of the sample decreases,and the energy loss rate increases significantly.The primary and secondary crack penetration ratio determines the final failure mode of the sample,when the penetration ratio of the cracks is small,the crack initiation-expansion of the cross-jointed specimen is mainly controlled by the main cracks.When the penetration ratio is greater than 0.67,the interaction between the primary and secondary cracks is obvious,and the formation of the sample is composed of primary and secondary multiple fracture surfaces composed of anti-wing cracks and coplanar cracks.Under the action of bidirectional constant pressure,the anti-wing cracks penetrate at the tip of the primary and secondary cracks of the sample,and finally show shear failure.Under the two-way unequal confining pressure,the test sample presents delamination,peeling and block failure approximately perpendicular to the direction of the minimum principal stress,and the overall performance is compressive shear failure.
rock mechanicscross cracksBHPBcoupled static and dynamic loadsfailure modeDIC
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