三向受压混凝土的动态特性研究

为探究混凝土在三向受压状态下的动态特性,利用自行研制的大型多功能三轴材料试验机,进行不同应变速率(10^-5/s、10^-4/s、10^-3/s、10^-2/s)下混凝土不同定侧压比(1:1、2:1、3:1、4:1)的动态真三轴抗压试验,研究了混凝土在动态抗压下的强度和变形特性。结果表明:混凝土在三向受压状态下表现出明显的应变率效应,峰值应力随着应变速率的增加先减小后增大,峰值应力减小最大幅度为5.42%而后开始增大,最大增幅为18.22%。而峰值应力随着侧压比的增大而增大,到达3:1时应力速率敏感性降低。混凝土的峰值应变在低侧压比(1:1和2:1)时随着应变速率的增加而减小,而在侧压比较高(3:1和4:1)时先减小再增大。随着应变速率的增加,裂纹开始从骨料处产生,塑性应变增大,导致峰值应变增大;在动态加载条件下,峰值应变随着侧压比的增大有先增大后减小的趋势。较高侧压比时混凝土的弹性模量随着应变速率的增加具有增大的趋势,最大增幅为240.66%。应力-应变曲线上升段随着应变速率增大越来越陡峭。试件的破坏形态随着侧压比的增大从柱状破坏变为斜剪破坏。

Dynamic characteristics of concrete under the triaxial compression

In order to explore the dynamic characteristics of concrete under three-dimensional compression,the dynamic true triaxial compression tests of concrete under different constant lateral compression ratios(1:1,2:1,3:1,4:1)at different strain rates(10^-5/s,10^-4/s,10^-3/s,10^-2/s)were carried out with a large multi-functional triaxial material testing machine.The strength and deformation characteristics of concrete under dynamic compression are studied.The results show that the concrete shows obvious strain rate effect under three-way compression.The peak stress first decreases and then increases with the increase of strain rate.The peak stress decreases by 5.42%and then begins to increase,with the maximum amplitude being 18.22%.The peak stress increases with the increase of the lateral pressure ratio,and the stress rate sensitivity decreases when it reaches 3:1.The peak strain of concrete decreases with the increase of strain rate at low lateral pressure ratios(1:1 and 2:1),but first decreases and then increases at higher lateral pressures(3:1 and 4:1).As the strain rate increases,cracks begin to occur from the aggregate,and the plastic strain increases,resulting in an increase in the peak strain.The peak strain tends to increase with the increase in the lateral pressure ratio.The elastic modulus of concrete tends to increase with the increase of strain rate,and the maximum increase is 240.66%.The rising section of the stress-strain curve becomes steeper and steeper as the strain rate increases.The failure mode of the specimen changes from columnar failure to oblique shear failure as the lateral pressure ratio increases.