三向应力状态下混凝土动态强度和变形特性研究

利用大连理工大学自行研制、改造的大型液压伺服静动三轴试验系统对立方体混凝土试件进行恒定围压下的动态三向压缩试验,侧向恒定围压分别为0MPa、4MPa、8MPa、12MPa、16MPa五个级别,应变速率分别为10-5/s、10-4/s和10-3/s三个量级,系统研究了不同恒定围压和应变速率对混凝土强度和变形特性的影响。试验表明:随着围压的增加,混凝土三轴极限抗压强度有明显的增强趋势;峰值应力处的应变值增加幅度显著。随着应变速率的增加,围压较低时,混凝土动态强度的增加趋势明显;围压较高时,动态强度随应变速率增加而增加的趋势减弱,特别是当围压值超过混凝土的单轴强度时,可以不考虑混凝土应变速率对混凝土强度的影响。得出了混凝土在不同应变速率以及不同恒定围压下的应力应变全过程曲线。

DYNAMIC STRENGTH AND DEFORMATION OF CONCRETE IN TRIAXIAL STRESS STATES

Dynamic compressive tests on cubic specimens were carried out on a servo-hydraulic multiaxial testing machine designed and manufactured at Dalian University of Technology, China. The lateral confining pressure was kept at constant values of 0MPa, 4MPa, 8MPa, 12MPa, 16MPa, respectively and the strain rates were 10^-5/s, 10^-4/s and 10^-3/s, respectively. The effect of strain rate and confining pressure on the strength and deformation of concrete were investigated systematically. From the test results it was revealed that the ultimate strength increased significantly as the confining pressure increased, and the increase in strain at peak stress was even more pronounced. At lower confining pressure, the ultimate strength increased definitely with the increasing strain rate, but the strength increment tended to become smaller at higher confinement; particularly when the confining pressures was higher than the quasi-static uniaxial compressive strength, the rate-dependent effect tended to diminish. The complete stress-strain curves at different strain rates were obtained.