Study On Dynamic Compression Properties Of Rock-steel Fiber Reinforced Concrete Composite Layer

The surrounding rock and supporting structure of the tunnel are often damaged due to the impact of earthquake,blasting and rock burst.In shotcrete anchor support structure,steel fiber concrete and surrounding rock are combined as a whole to provide support resistance and prevent excessive deformation of surrounding rock.In order to study the steel fiber reinforced concrete under the shock load on the protective effect of surrounding rock,rock,steel fiber concrete(different fraction and grade)and rock-steel fiber reinforced concrete composite layer static mechanics performance test of the dosage and concrete strength grade of steel fiber on the influence of static mechanics performance,based on Mohr’s strength criterion of rock-layer steel fiber reinforced concrete composite static strength prediction model;Using split hopkinson pressure bar(SHPB)of rock,the steel fiber reinforced concrete and rocksteel fiber reinforced concrete composite layer for six dynamic impact compression test under strain rate,strain rate and dynamic mechanical properties of steel fiber content on impact,based on the Mohr’s strength criterion and compound material mechanics to establish rock mixing rate-layer steel fiber reinforced concrete composite dynamic strength prediction model;The stress uniformity was verified by numerical simulation of SHPB test,and the stress-strain curve was reconstructed based on the results.The main contents and conclusions are as follows:(1)the static strength of the rock-steel fiber reinforced concrete composite layer increases with the increase of the strength grade of the concrete matrix and the steel fiber content,and the static strength is between rock and steel fiber reinforced concrete.The composite layer without fiber showed brittle failure characteristics,while the rock-steel fiber concrete composite layer showed ductile failure characteristics of overall cooperative deformation.The static strength prediction model of rock-steel fiber reinforced concrete composite layer based on Mohr strength criterion is established.(2)within the strain rate range of 35s-1-135s-1,the dynamic compressive strength,peak strain,DIF and dissipated energy of rock,steel fiber reinforced concrete and rock-steel fiber reinforced concrete composite layer have obvious strain rate effect under dynamic impact load,and dynamic mechanical property parameters increase with the increase of strain rate.Under the same strain rate,the dynamic compressive strength of the composite layer is between rock and steel fiber concrete,and the dissipation energy is about the sum of the two.Steel fiber can effectively enhance the dynamic mechanical properties of the composite layer,and the rock-steel fiber concrete composite layer of C40 has better dynamic mechanical properties.A dynamic strength prediction model for rock-steel fiber reinforced concrete composite layer was established based on Mohr strength criterion and composite mechanical mixing rate.(3)in the strain rate range of 35s-1-135s-1 the failure of rock-steel fiber reinforced concrete composite layer specimens shows four types as the strain rate increases:when the strain rate is around 35s-1,the failure of rock layer does not occur,while the failure of tensile strain occurs around the concrete layer;When the strain rate increases to about 55s-1,the axial crack between the rock layer and the concrete layer is formed.When the strain rate is about 95s-1,the rock-concrete shows the failure of retaining core.In the vicinity of 135s-1 strain rate,the composite layer is broken as a whole.(4)SHPB numerical simulation shows that the waveform curves extracted at different positions of the specimen have a high degree of coincidence,and the stress uniformity of the specimen is good.The reconstructed stress-strain curve is in good agreement with the stress-strain obtained from the test.The failure process of rock-steel fiber reinforced concrete composite layer is from tensile strain failure to axial splitting failure,and then to integral fracture.Rock-the impact resistance of steel fiber reinforced concrete composite layer is related to the safety and stability of the roadway surrounding rock and supporting structure,to study the dynamic mechanical properties of composite layer for supporting structure under impact loading mechanism provides research foundation,to design good anti-seismic,antiknock performance,higher safety factor supporting structure to provide the reference.