Damage and Failure Characteristics and Constitutive Model of Copper-Bearing Skarns Disturbed by Hierarchical Dynamic Loading After Loading And Unloading

To simulate the uploading rates, original rock stress and hierarchical blasting disturbance intensity during excavation, methods considering density, unloading rate, preloading axial and impact air pressure were applied to copper-bearing skarn to study the hierarchical dynamic load disturbance based on blasting mining conditions of deep mineral resources. First, the stress-strain curves had stage characteristics, which were obtained by the test analysis of the deformation characteristics and damage failure modes of copper-bearing skarn. Specifically, the compaction and elastic deformation occurred in only the loading and unloading stage, but the elastic and plastic deformation and macroscopic failure occurred successively in the impact loading stage. The primary factor leading to the macroscopic failure of copper-bearing skarns was the impact dynamic load. It also promoted the cracks to germinate at the incident end of the rock sample, expand and penetrate along the propagation direction of the impact stress wave, leading to the failure mode of the sample with primarily tensile failure and supplementing by compression-shear and frictional failure. Then, the damage variables of copper-bearing skarn were defined in stages based on the force deformation mechanism of the sample, and the damage variable equations corresponding to the loading and unloading stage and impact loading stage were deduced. Combined with the test data, the damage variable-strain curves of each stage showed an S shaped trend, which was consistent with the slow-rapid-slow increase in the damage degree of copper-bearing skarn under static and dynamic loads and remained constant. Finally, based on assumptions such as strain equivalence, the constitutive model of copper-bearing skarn was established in stages after loading and unloading with hierarchical dynamic load disturbance, and the constitutive equation was verified by test data. The obtained results showed that the theoretical and test stress-strain curves had a preferable consistency.

Automated summary

In this study, methods considering density, unloading rate, preloading axial and impact air pressure were applied to investigate hierarchical dynamic load disturbance based on blasting mining conditions of deep mineral resources. Stress-strain curves of copper-bearing skarn, obtained through test analysis, showed characteristics that varied in different stages. Macroscopic failure of the rock sample was primarily caused by impact dynamics load, leading to tensile failure supplemented by compression-shear and frictional failure. Damage variables were defined based on force deformation mechanism, and corresponding equations for loading-unloading stage and impact loading stage were deduced. Verification using test data showed good consistency between the theoretical and test stress-strain curves.