Study On Mechanical Properties And Energy Dissipation Characteristics Of SAP Porous Concrete

SAP(Super Absorbent Polymers,referred to as SAP)porous concrete has the characteristics of low cost,convenient construction and environmental friendliness due to its unique poreforming method.It has broad application prospects in filling mining,military protection engineering,construction engineering and other fields.In order to further study the mechanical properties and energy dissipation characteristics of SAP porous concrete materials,nine kinds of SAP porous concrete with three pore diameters(2mm,5mm,8mm)and three porosity ratios(40%,50%,60%)were prepared.concrete material.The static uniaxial experiment of SAP porous concrete,SHPB experiment,underwater explosion experiment and numerical simulation of underwater explosion experiment were carried out.The main achievements are as follows:MTS material testing machine was used to study the mechanical properties and energy dissipation characteristics of SAP porous concrete under one-dimensional strain loading.The results showed that in the elastic stage: the elastic modulus of SAP porous concrete decreased with the increase of porosity,and with the increase of the pore size increases,and the porosity has the greatest influence on the elastic modulus of the material.The elastic modulus of the2 mm sample with 60% porosity is the smallest,which is 14MPa;the elastic modulus of the8 mm sample with 40% porosity is the largest,which is 178 MPa.In the platform stage: with the increase of porosity,the length of the stress platform increases,and the amplitude of the platform stress decreases.The platform stress of the 2mm sample with 60% porosity is the smallest,which is 1.4Mpa;the 8mm sample with 40% porosity The platform stress is the largest,which is 8.8MPa.In terms of energy absorption,when the pore size is the same,the energy absorption value decreases with the increase of porosity,and the energy absorption value of the 8mm pore diameter sample is the largest at 40% porosity,reaching 2.56MJ/m3;the peak energy absorption efficiency It increases with the increase of pore size,and when the stress value is 1.76 MPa,the peak energy absorption efficiency of the 8-60 sample reaches the maximum,which is 25.9%.The dynamic mechanical properties and energy dissipation characteristics of SAP porous concrete with different specifications under one-dimensional strain loading under high strain rate(346～579s-1)were studied by using the SHPB experimental device.The results show that SAP porous concrete has an obvious strain rate effect,and the smaller the porosity and the larger the pore size,the more obvious the enhancement effect on the dynamic yield strength.In terms of energy dissipation,the energy dissipation WL and crushing energy dissipation density Wd of porous concrete with different specifications increase with the increase of incident energy,but the energy dissipation rate α is limited by the energy dissipation capacity of porous concrete.It does not increase proportionally to the incident energy.In addition,the larger the porosity,the smaller the energy dissipation value of porous concrete,but the effect of pore size on energy dissipation is not significant.By comparing and analyzing the energy dissipation value of SAP porous concrete under static and dynamic conditions,it is found that the energy dissipation value under static condition is significantly greater than the dynamic energy dissipation value.Under dynamic conditions,under the impact pressure of 0.4MPa,the energy dissipation value of porous concrete with a porosity of 40% and a diameter of 8mm is the largest,which is only 21.25% of the static energy dissipation value.Through the anti-explosion experiment of SAP porous concrete,the failure process and the attenuation law of the secondary shock wave at the back of porous concrete are studied at higher strain rates.The results show that under the action of explosive load,the integrity of porous concrete with the same porosity is 5mm,2mm,and 8mm in order from good to bad.In addition,the back secondary shock wave intensity of SAP porous concrete with 3 kinds of pore diameters decreases with the increase of porosity,among them,the porous concrete with8 mm pore diameter with 60% porosity is completely compacted under the action of explosive load,so its impact on the attenuation effect of the secondary shock wave is the best.According to the strain value of the porous concrete back plate along the radial direction,the strain value at the boundary is greater than the strain value in the central area,and the reason is that there is a large plastic deformation caused by local shear at the boundary of the back plate.In order to further analyze the anti-explosion process of SAP porous concrete,LS-DYNA is used to carry out numerical calculation on the anti-explosion experiment of SAP porous concrete.The results show that: with the decrease of porosity,the proportion of dissipated energy of porous concrete to the total energy increases from 54.61% to 61.73%,and the proportion of panel dissipated energy decreases from 30.78% to 23.52%.The influence of the plate energy dissipation is not obvious.In addition,the one-dimensional shock wave management theory is used to calculate and analyze the secondary shock wave in the sealed cabin.The results show that: when the porosity of porous concrete is 40%,the theoretical calculation of the back secondary shock wave overpressure is close to the numerical value.However,the theoretical value of one-dimensional shock management gradually increases with the increase of porosity,which is opposite to the trend of the simulated value.This may be because the one-dimensional shock management theory only considers the generation of secondary shock waves in the airtight cabin is likely to be the result of the coupling effect of the stress wave transmission and the motion of the back plate.