Research On The Dynamic Response Characteristics Of Cemented Backfills With Different Strengths Under Dynamic Loads

Cementing filling body in the underground complex environment not only affected by itself and the surrounding rock mass produced by static load,and in the neighboring roadway excavation work,blasting and excavation of dynamic loads on the cemented filling body,often make the structure of cementing filling body in different degree of damage,a slope peeling,even instability phenomenon such as collapse,seriously affect the safety of pillaring work.In order to study the cemented filling body dynamics characteristic under different condition,using the split hopkinson pressure bar test technique for regular uniaxial impact experiment and three dimensional movement combination load impact test,study the cement content,the average loading strain rate and confining pressure strength of cementing filling body dynamic axis,stress strain curve,impact the original waveform diagram and the failure modes,failure energy characteristics,etc.The influence of the dynamic mechanical properties.And obtained the following results:?1?In the process of uniaxial experiment,found the same cement content of cementing filling body under different loading strain rate effect,its original wave peak of the incident wave as well as the size and the loading strain rate of the energy of the incident wave size have strong correlation,and with the increase of loading strain rate,incidence peak value and energy also increases gradually;According to the characteristics of stress-strain curve,the phenomenon of"stress jump"at the front end of the curve is analyzed.The variation law of"stress jump"value was obtained when the strain rate increased under the same cement content.?2?the response degree of cemented backfill varies with different strain rates.When the strain rate increased from 23.8 s^-1 to 32.2s^-1,the stress peak increased from 4.98Mpa to 8.12 MPa,an increase of 63.1%.When the strain rate increased from 32.2s^-1 to 36.5s^-1,the stress peak increased from 8.12Mpa to 11.7Mpa,an increase of 44.1%.When the strain rate continues to increase,the stress peak begins to decrease.?3?In the three-dimensional combined loading experiment,under different impact strain rates,the magnitude of the incident wave peak of the consolidated backfill showed significant differences in the original waveform,and the variation law was positively correlated with the magnitude of the loading strain rate.Under the action of axial and confining pressure,with the increase of impact load,the failure peak stress of the same cemented backfill increases first and then decreases.?4?It can be seen from the stress-strain curve that under three-dimensional combined loading,the beginning of the curve does not have obvious crack compaction stage like the traditional stress-strain curve of uniaxial impact experiment,but directly rises to the failure characteristic of elastic deformation stage.This is because the cementing backfill specimen was subjected to a certain strength of static loading before impact in axial and circumferential directions,so that the backfill specimen entered into the crack compaction stage in advance when subjected to dynamic loading.And according to the comparison,when static pressure with different strengths is applied in advance,when the specimens are subjected to different dynamic loads,the dynamic strength of cemented backfill is different.?5?In the three-dimensional combined loading experiment,when the loading strain rate of the same cemented backfill increased,its dynamic strength first increased and then decreased.Moreover,when the loading strain rate was 70s^-1 or so,the dynamic strength growth rate of the specimen reached a peak of 13%,and the critical value of the dynamic strength of the cemented backfill was 14.8Mpa.