In order to present basic guidance for system calibration of split Hopkinson pressure bar(SHPB) with the special shape striker,wave characteristics and dynamic responses of SHPB under striker impact were analyzed.Stress generated by the special shape striker tends to have a half-sine waveform and has little wave dispersion during its propagation.Impact velocities of the special shape striker and peak values of generated stress still have linear relation but with a different coefficient from that of cylindrical strikers.From stress histories on the surfaces of the input bar impacted by the special shape striker off-axially and obliquely,it is found that the misalignment impacts usually trigger wave distortion and amplitude decrease,which can be used to identify the poor system adjustment.Finally,the system calibration of SHPB with the special shape striker can be classified into four steps:system adjustment,wave distortion identification,measurement calibration and transmission calibration,where the measurement calibration factor and transmission calibration factor are elaborated and redefined.
Xinli district of Sanshandao Gold Mine is the first subsea metal mine in China.To achieve 6 kt/d production capacity under the premise of safe mining,high-intensity mining might destroy the in-situ stress filed and the stability of rockmass.According to sampling and testing of ore-rock and backfill and in-situ stress field measurement,safety factor method calculation model based on stress-strain strength reduction at arbitrary points and Mohr-Coulomb yield criterion was established and limit displacement subsidence values under the safety factor of different limit stoping steps were calculated.The results from three years in-situ mining and strata movement monitoring using multi-point displacements meter showed that the lower settlement frame stope hierarchical level filling mining method,mining sequence are reasonable and rockmass stability evaluation using safety factor method,in-situ real-time monitoring can provide the technical foundation for the safety of seabed mining.
