Study On The Dynamic Response And Strain Field Evolution Of Sika Ore In Natural-saturated Environmen

With the increasing demand for mineral resources,the mining environment of mineral resources is also facing many challenges.The most critical environmental change of Niukutou open-pit lead-zinc mine in Qinghai is saturation rock mass,and the dynamic mechanical properties of rock mass in natural-saturation environment are the main factors affecting blasting parameters.At present,there are no dynamic mechanical parameters of rock in mines,which cannot meet the needs of numerical simulation and parameter optimization of water hole blasting.Therefore,it is urgent to study the dynamic response law of ore rock in natural-saturation environment.Based on the project of"Research on Key Technology of Water Hole Blasting and Slope Presplitting Blasting in Niukutou Open-pit Stope",this paper takes the skarn rock at 3516 elevation water gushing in M1 ore body 4 area of Niukutou Open-pit Stope as the research object,and uses SHPB system to carry out impact test on skarn rock specimens in natural-saturation environment.The dynamic response law and fractal law are studied,and the evolution law of strain field is studied by DIC technology.The main research results are as follows:（1）Under uniaxial impact load,the stress-strain curves of the natural rich water environment skarn rock specimens exhibit good linear elastic characteristics.Among them,the elastic yield stage of the rich water ore rock lasts for a long time,and the trend after the peak is relatively slow.This is consistent with the rock breaking effect of the natural rich water environment skarn rock section in on-site blasting operations.The transmission ability of stress wave in the specimen is weakened,the reflection ability is enhanced,and the change range of internal absorption energy is small.When the strain rate is between=59.33～128.24 s^-1,the critical compressive strength of ore rock in natural-rich water environment is:σ_dn=74.19 MPa,σ_ds=56.12 MPa,softening coefficientη=0.81～0.88.The fractal dimension is:D_n=1.61～2.33,D_s=1.67～2.27.The fractal dimension is positively correlated with the dynamic compressive strength and the energy absorption density per unit volume,which means that controlling the energy within the corresponding range is conducive to improving the blasting effect of skarn in the natural water rich state.Through the analysis of the fracture surface of the specimen,it is found that the cement of the fracture surface of the saturation sample is obviously lost,and the roughness increases by about 52%～120%.The_nD^x=1.59,1.94,2.03,2.10,2.21,_sD^x=1.61,1.76,1.88,2.01,2.12,and the macro-meso fractal dimension of the saturation specimen is calculated by the box dimension.The overall difference is small,and the maximum is 6.61%.（2）Under the condition of axial pressure of 3MPa and confining pressure of 1MPa,when=59.21s^-1～75.00s^-1,σ_d decreases by about 12.01%-26.24%,and the dynamic compressive strength of rock decreases with the decrease of strain rate.When=75.00 s^-1～87.42 s^-1,σ_d decreases by 8.68%～12.01%,and dynamic compressive strength is greatly affected by water content.When=87.42 s^-1～97.87 s^-1,σ_d is relatively reduced by about8.68%～9.83%,the curve appears to be separated,and the dynamic compressive strength decreases with the increase of strain rate.The softening coefficientηis between 0.84 and0.92,and has a slow growth trend.With the increase of strain rate,the energy also increases.After the rock is rich in water,the transmission energy decreases and the reflection energy increases.The dynamic compressive strength increases linearly with the energy absorption density per unit volume.The critical compressive strength isσ_dn=98.43 MPa andσ_ds=62.60 MPa.The macroscopic failure types are mainly shear failure,peripheral,multiple tensile shear and a small amount of splitting failure.At low strain rate,the damage degree of ore rock specimens in the two states is not much different.At high strain rate,the macroscopic cracks of saturation skarn rock are more distributed and the crushing is more serious.（3）Through high-speed photography,it is found that the macroscopic damage of natural-saturation skarn rock under different impact velocities is mostly axial splitting failure,and radial tensile shear failure gradually occurs with the increase of velocity.According to the results of DIC analysis,it is found that the displacement field evolution law of natural-saturation skarn ore rock under different impact velocities is basically the same.The critical displacement and critical micro-strain values of the specimen are closely related to the impact velocity,and all show a positive growth of the concave curve.The increase amplitude shows a trend of decreasing first and then increasing.Among them,the strain field evolution is mainly divided into three stages:initial strain stage,local strain stage and strain failure stage.When roughly the same,the critical displacement of the specimen after saturation with an average increase of 47.55%.The critical strain value with an average increase of 6.86%,which further indicates that the internal accumulated energy of the saturation specimen is more used in the micro-deformation stage when subjected to external load.In on-site blasting operations,more explosive energy is required to increase the unit consumption of explosives in order to achieve better blasting effects.