落石冲击UHPC棚洞板砂土层缓冲性能研究

Study on Cushion Effect of Sandy Soil Layer on the Ultra High Performance Concrete Shed Slab under Rockfall Impact

砂土作为常用的缓冲材料,广泛用于山区落石防护结构。为评估其对落石冲击UHPC棚洞板的缓冲性能,运用LS-DYNA软件建立UHPC棚洞板及不同厚度砂土层的有限元模型,分别模拟50,100,150,200 kJ能级下的落石冲击作用,在此基础上从落石冲击力、砂土层耗能比例、板的动力响应等多方面对比不同厚度砂土层的缓冲性能。结果表明:(1)60 cm厚砂土层下,各能级落石冲击力峰值较30 cm厚砂土层时降幅均超过40%,90 cm厚砂土层下,各能级落石冲击力峰值降幅相对变缓,而结构恒载却显著增加;(2)60 cm和90 cm厚砂土层下,各能级砂土层耗能比例均已超过90%,混凝土主压应力峰值和钢筋拉应力峰值均不超过材料强度,且在相同能级下的对应数值差距很小;(3)60 cm是较为适宜的砂土层厚度,能够满足200 kJ能级的防护要求。

Sandy soil is widely used as common buffer material in mountainous rockfall protection structures.In order to assess its cushion effect on the ultra high performance concrete shed slab under rockfall impact,LS-DYNA software is used to establish finite element model of UHPC shed slab and sandy soil of different thickness to simulate rockfall impact at 50,100,150 kJ and 200 kJ energy levels respectively.Cushion effect of sandy soil with different thickness is compared in terms of rockfall impact force,energy dissipation ratio of sandy soil and dynamic response of the slab.The results show that:(1)The maximum rockfall impact forces of various energy levels under 60 cm sandy soil layer decline over 40%compared with those under 30 cm sandy soil layer.The maximum rockfall impact forces of various energy levels under 90 cm sandy soil layer go down relatively slowly,while structure dead load increases significantly.(2)Under 60 and 90 cm sandy soil layers,energy dissipation ratios for sandy soil of various energy levels are all more than 90%,both the maximum principal compressive stress for concrete and the maximum tensile stress for rebar do not exceed material strength,while the differences in corresponding numerical values are very small.(3)60 cm is a suitable thickness for sandy soil layer,which can satisfy protection requirements of 200 kJ energy level.