Study On Rock Accumulation Damage Under Cyclic Dynamic Loading

Being a large resource-consuming country,China depends on its own mining as a major way for mineral obtaining rather than imports.The inseparable consequence,which come from blasting to stripping,from advancing to producing,serves as the principle dynamic loading form for mine production.Such kind of loading action not only fulfills the demand for mine production,but also impacts on rock mass which is not targeted for blasting around.Burdening irregular circulation of such dynamic loading,mechanical property of those rock masses must be deteriorating.Therefore,the writer uses a domestic SHPB device to demonstrate dynamic loading by circulated impacts,so as to illustrate the evolution rule of accumulative damage on rock mass.Guidelines of this article are as followed:(1)Under cyclic dynamic loading at 0.04 MPa,0.06 MPa,0.08 MPa and 0.10 MPa impact on specimens respectively,and the writer got each specimen peak stress-strain curve and the dynamic changing.The under-test material showed a stress at dynamic peak declining as impacts accumulated and The peak strain of the final impact is the maximum and increasing as impacts accumulated.It was summarized that the peak strain of the under-test material after impacts was generally in a positive correlation with the frequency of cyclic loading and strain rate moved in an upstream tendency with higher impact pressure and accumulated circulations.(2)The writer explored variable responses of under-test materials at different length-diameter ratio to dynamic loading since rock mass was in different shapes in actual mining engineering.Based on relevant matching of experimental result that the specimen length to diameter ratio of 2.0 specimen worst is 0.5867,the fit of the specimens of length to diameter ratio of 2.6,the optimal is 0.8740.It was revealed that the bigger the length-diameter ratio was,the higher dependence the under-test material showed to strain rate.Additionally,longer length of the under-test material burdened lower dynamic loading.(3)In engineering practices,large and small blasting operations alternate for production.Therefore,different impact pressures could be utilized to alternate dynamic loading at different extents.A comparison of stress-strain curves was taken between variable and constant dynamic loading.Given by apparent fragments on under-test materials,such comparison was aimed at analyzing the different damages upon which given by two loading forms.(4)This article demonstrated a sonic wave test conducted to explore the downside of longitudinal wave velocity of the rock mass under cycle dynamic loading and explored the definitions of different damage variations and sought out a proper way to define damage variation in terms of accumulative damages.It was concluded that the damage variation defined from longitudinal wave velocity was able to represent the evolution of accumulative damage on rock mass under cyclic dynamic loading.This article also illustrated different accumulative damages on rock mass resulted from dynamic loading at single and variable pneumatic impact circulation.