Study On Dynamic Response Characteristics Of Deeply Buried Metamorphic Limestone In Dahongshan Copper Mine

The stress state of the deep surrounding rock is complex,not only from the self-gravity of the overlying rock mass,but also from the lateral pressure brought by the surrounding rock mass,which brings a huge test to the blasting and excavation of the roadway.Therefore,it is urgently needed to grasp the response law of deep surrounding rock under dynamic load,provide a theoretical basis for the optimization of blasting parameters of underground roadway excavation.In order to study the dynamic mechanical characteristics of the deep surrounding rock,this paper combined with the Dahongshan Copper Mine's "Key Technology Research on the Control of Blasting Residues in Roadway Excavation".The metamorphic limestone in the surrounding rock of 370 horizontal roadways was selected as the research object,through conventional uniaxial impact Experiments and three-dimensional dynamic and static combined loading impact tests,numerical simulations and other methods to study the dynamic mechanical properties of loading strain rate,axial static pressure,confining pressure on the dynamic strength of deep surrounding rock,stress-strain curve,failure mode,and energy dissipation law influences.The main research conclusions are as follows:(1)In conventional uniaxial impact tests,the fracture degree of metamorphic limestone increases obviously with the increase of loading strain rate.When the loading strain rate is 17s-1,the degree of rock fragmentation is relatively low or no damage occurs.When the loading strain rate is 26s-1?56s-1,the broken body is mainly columnar splitting structure and conical structure,and the failure mode is typical tensile failure.When the loading strain rate is increased to 68s"1,the rock fragmentation degree is relatively low.The number of cone-shaped and small particle size breakages increases obviously,which indicates that the rock samples gradually transition from tensile failure to shear failure.(2)In the conventional uniaxial impact test,the loading strain rate affects the fractal characteristics of rock sample fragmentation.When the loading strain rate is 28s-1,34s-1,56s-1,68s"1,the fractal dimensions are 1.73 respectively,1.82,2.24 and 2.31;the loading strain rate is positively correlated with the fractal dimension,but the fractal dimension gradually slows down as the loading strain rate increases,and the two are in a functional relationship Df=-1.536e-4?2+0.028?+1.062.(3)From the energy point of view,the reason for the failure of rock specimens under conventional uniaxial impact conditions is explained.The greater the energy density,the more severe the damage of the rock;the energy density of the rock has obvious strain rate correlation,and the energy density of metamorphic limestone varies with Strain rate shows a linear growth trend.(4)in a three-dimensional movement combination load experiment,in the case of fixed confining pressure,axial static pressure within the range of 22.49?40.2 Mpa,sodic tuff of elastic modulus and composite compressive strength and the law of the axial static pressure first increases and then decreases,the axial static pressure is 34.4 Mpa,the confining pressure is 8 Mpa maximum modulus of elasticity of 68.68 Gpa 177.36 Mpa and combination of maximum compressive strength;Under the condition of fixed axial static pressure,the elastic modulus of rock and the combined compressive strength have a positive correlation with the confining pressure.(5)In the three-dimensional dynamic and static combined loading test,under the condition of constant confining pressure,the axial static pressure is in the range of 22.49?40.2Mpa.The elastic modulus and combined compressive strength of metamorphic limestone show up with the increase of axial static pressure.When the axial static pressure is 34.4Mpa and the confining pressure is 8Mpa,the maximum elastic modulus of 68.68Gpa and the maximum combined compressive strength of 177.36Mpa are reached;under the condition of fixed axial static pressure,the rock's Elastic modulus,combined compressive strength and confining pressure are positively correlated.(6)Based on the original HJC model parameters,the HJC parameters suitable for this article are calculated,and the conventional uniaxial impact test of metamorphic limestone is numerically simulated using ANSYS/LS-DYNA finite element software.Internal stress state and failure process;quantitatively characterize the damage value d of metamorphic limestone when the bullet impact velocity is 3.68 m/s,7.42 m/s,9.26 m/s,12.78 m/s and 14.98 m/s through the microcrack density method They are 0.02,0.14,0.35,0.53 and 0.64 respectively.