Study On Anti-explosion Performance Of Steel Fiber Reinforced Concrete Lining In Underground Tunnel

With the gradual improvement of China's transportation network,the number of tunnels has increased rapidly.Chemical explosions in tunnels have occurred,causing serious damage to the tunnel lining and even causing tunnel collapse.Most of the tunnels in China use ordinary concrete materials.Mainly considering its anti-seismic load effect,the internal anti-explosion performance is rarely considered.Therefore,studying the blast resistance of lining layer is of great significance for tunnel protection design.On the basis of considering the high strength and high crack resistance of the tunnel lining material,this paper puts forward the idea that steel fiber reinforced concrete is used as a lining layer to resist the internal explosion of the tunnel.The research contents and conclusions of this paper mainly include:(1)Static mechanical experiments were carried out on steel fiber reinforced concrete and ordinary concrete by MTS universal testing machine.The experimental results show that the steel fiber reinforced concrete with a volume content of 2% can withstand a maximum load of 2.256 times that of ordinary concrete;and the failure mode of steel fiber reinforced concrete is tearing,and the failure mode of ordinary concrete is fragmentation..At the same time,the material parameters such as maximum stress,peak strain,elastic modulus and Poisson's ratio of the two concretes were obtained,which laid a foundation for the establishment of numerical simulation materials.(2)The dynamic mechanical tests of steel fiber reinforced concrete and ordinary concrete under different strain rates were carried out by SHPB,and the stress-strain curves and failure modes were obtained.The experiment shows that the steel fiber reinforced concrete 214.86 s-1 strain rate starts to appear cracks at the macroscopic level,and the powdery fragments begin to appear when the strain rate is 483.12 s-1;the ordinary concrete breaks into a large number of fragments at the strain rate of 116.01 s-1,352.15 Powdery fragments begin to appear at the s-1 strain rate.The stress peaks of both concretes increase with the increase of strain rate,indicating that both concretes are strain rate sensitive materials.The dynamic growth factor(DIF)of the two concretes increases with the increase of the strain rate.Similar to the peak stress,there is a good linear relationship between the dynamic growth factor and the strain rate.(3)By introducing the dimension,the dynamic constitutive equation of Zhu-Wang-Tang is further simplified.When the accuracy is satisfied,only four parameters are obtained,and the dynamic stress-strain relationship before the peak stress of steel fiber reinforced concrete is established.The constitutive equation,the parameters of the constitutive model are obtained by the fitting method.(4)The anti-explosion performance of the two concretes as tunnel lining layers was studied by numerical simulation software.In order to ensure the accuracy of the simulation,the real data measured by MTS and SHPB experiments were imported into the CDP model.The simulation results show that under the conditions of 20 kg,40kg,60 kg,80kg,100 kg,200kg,400 kg,600kg,800 kg and 1000 kgTNT,the maximum equivalent plastic strain of the steel fiber reinforced concrete as the lining layer is the model of ordinary concrete as the lining layer.70.15%,40.49%,30.08%,18.48%,11.31%,11.85%,18.47%,21.22%,23.39%,27.01% of the effective plastic strain,indicating that the steel fiber concrete as a tunnel lining layer has better antiknock performance than ordinary Concrete acts as a tunnel lining.