Research On Mechanical Properties And Anti-explosion、Seismic Performance Of EPS Concrete

EPS concrete is relatively new building materials that are being used increasingly in many applications of modern construction owing to the advantage that lower density、anti-explosion capabilities、seismic capability.For this reasons,the mechanical behaviours and energy absorption characteristics of EPS concrete become one of the most attractive topics in mechanics and materials sciences.Firstly the quasi-static compressive and quasi-static splitting experiments have been carried out to investigate the mechanical behavior of EPS concrete with different size and containing of EPS beads.the characteristics of compressive stress-strain curves of EPS concrete with different containing of EPS beads have been investigated.an experimental investigation was conducted on EPS concrete having porosites ranging from10%to40%and containg two EPS bead sizes to confirming the presence of an particle size effect on the EPS concrete compressive strength.the effect of EPS concrete containing silica fume ranging from20%to40%on compressive strength has been investigated.the relativeship between relative compressive strength(the ratio of two compressive strengths of EPS concrete and matrix) and relative splitting strength(the ratio of two splitting strengths of EPS concrete and matrix) was builden.the effect of different calculation methods(the classic linear-elastic approach and the fracture mechanics approach)on the quasi-static splitting strength is analyzed.the relativeship between the compressive strength and splitting strength was builden. the feature of compressive deformation deformation is analysized.A split Hopkinson pressure bar(SHPB) was employed to study the dynamic characteiteristics of EPS concrete for different size and containing of EPS beads. The results show that the characteiteristics of EPS concrete is sensitive to strain rate under the loading conditions in this study.The stress-strain relationship of EPS concrete exhibited three different regions:linear-elasticity deformation due to bending of the cell walls; the plateau stress as result of plastic buckling of the cell walls and plastic collapse of the cells; and this behavior was gradually vanished as strain rates increased. The plasic characteiteristics of small EPS bead sizes concrete for the same EPS volume fraction is more evident,in this study,the physical origin is identified for this phenomenon. the particle size effect becomes negligible for very high EPS volume fraction concretes. the post "peak-stress" behavior of EPS concretes is very evident with the increasing of strain-rate in that the EPS particle viscoelatic behavior. In order to investigate the splitting strength of EPS concrete with different size and containing of EPS beads,the Brazilian disc specimens were subjected to diametral impact with different projectile speeds by using the split Hopkinson pressure bar(SHPB)of74mm in diameter.the validity of dynamic split tension tests has been confirmed by accurate design padding block among incident bar、specimen、 transimitted bar,in order to prevent the two end of specimen from being crushed. proper pulse shapers were chosen in order to get enough time for specimen to reach an equilibrium state of stress during the SHPB experiment. the result show:the spiltting strength increases with stress rate increase, the spiltting test results have confirmed the presence of a particle size effect which is related to the EPS bead size on the EPS concrete spiltting strength with very high densities and becomes minimal with very low densities.the broken mode of EPS concrete was analysised.The shock wave attenuation in the tunnel with buffer of EPS concrete is simulated by LS-DYNA.firstly a numerical model using the program LS-DYNA is described that was used to simulate the anti-explosion response of a tunnel model with buffer of EPS concrete ranging form30%to40%.the results of simulation show: the peak for pressure above the tunnel can be decreased with the increase of the buffer layer thick, an empirical formula is proposed to correlate decay factor to the relative distance and the density of buffer materials.A numerical model using the program LS-DYNA is described that was used to simulate the dynamic response of a tunnel model with EPS concrete seismic buffer.the results indicate that the pressure and max principal stress above the tunnel and in the middle of the tunnel with buffer can be decreased. the pressure and max principal stress above the tunnel and in the middle of the tunnel with buffer follow an exponential attenuation relation with the thickness of buffer materials.