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| Experimental study on mechanical properties and failure laws of granite with an artificial flaw under coupled static and dynamic loads |
| LI Diyuan，HU Chuwei，ZHU Quanqi#br# |
(School of Resources and Safety Engineering，Central South University，Changsha，Hunan 410083，China)
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Abstract In order to study mechanical properties and failure laws of deep fractured rock mass under coupled static and dynamic loads，cylindrical granite specimens of 50 mm×50 mm were manufactured with a single artificial flaw. Coupled static and dynamic loads tests were carried out with a modified split Hopkinson pressure bar(SHPB) apparatus，and six typical levels of axial pre-stresses and three levels of impact pressures were designed. Three-dimensional digital image correlation(3D-DIC) was also applied to record and analyze the fracturing process and damage evolution of specimens. The test results show that the strength of the fractured specimen is obviously smaller than that of the intact specimen，and that，with increasing the axial pre-stress，the dynamic strength and dynamic elastic modulus generally increase first and then decrease，the combined strength generally increases while the dynamic strain generally decreases. Both the dynamic strength and the combined strength increase with increasing the impact pressure，showing that the granite has significant strain rate effect. The energy absorption ratio increases first and then decreases with increasing the axial pre-stress，but specimens will in turn release energy when the axial pre-stress ratio is 0.6–0.7. Besides，the greater the axial pre-stress is，the smaller the impact pressure is required to release energy，reflecting the characteristic of rockburst. The energy absorption ratio decreases with increasing the impact pressure. For intact specimens，high strain localization is concentrated at the end of the specimens and tensile cracks are formed，eventually causing splitting tensile failure of the specimens. For specimens with an artificial flaw，high strain localization is concentrated at the tip of the flaw or nearby，and wing cracks are formed，eventually causing combined tensile-shear failure of the specimens under coupled static and dynamic loads(axial pre-stress 0–30 MPa). However，two nearly parallel anti-wing cracks are formed at the tip of the flaw under coupled static and dynamic loads(axial pre-stress 50–70 MPa) due to the end effect，eventually causing shear failure of the specimens.
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2020, Vol. 39 
