不同尺寸混凝土试件受压状态下超声波传播特性研究

研究了不同尺寸混凝土试件在单轴压应力作用下,超声波波速的变化规律.试验所用试件有3种:采用大坝原级配最大骨料粒径为80 mm的棱柱体试件以及相应的湿筛混凝土试件,尺寸分别为25 cm×25 cm×50 cm、15 cm×15 cm×30 cm、10 cm×10 cm×20 cm.通过试验首先得到了加载过程中波速变化与应力水平的关系,然后基于超声波波速定义了损伤变量以评价加载过程中混凝土的损伤程度,并且根据试验提出了一种使用超声波法估测复杂应力下混凝土裂缝开展的方法.试验分析表明,混凝土内超声波衰减规律与骨料尺寸和数量以及试件尺寸等因素有关,所得结论对于评估大体积混凝土结构在复杂应力条件下损伤演变具有一定的应用价值.

Ultrasonic pulses behavior in various-size concrete specimens under compression

The attenuation of ultrasonic pulse velocity in various-size concrete specimens under uniaxial compression loading is investigated. Tests were conducted on prisms of 25 cm×25 cm×50 cm fabricated with dam concrete(maximum aggregate of 80 mm),and standard 15 cm×15 cm×30 cm prisms, 10 cm×10 cm×20 cm prisms which were made with the wet-screened components of dam concrete. First of all, special plots, showing the relation between the velocity through concrete and the stress during loading, have been introduced. Then a damage variable is defined based on the ultrasonic velocity attenuation and used to describe the growth law of damage during loading. At last, a general method to evaluate the evolution of crack in concrete is presented. Results show that the rule of ultrasonic propagation in concrete is apparently affected by the scale effect and the effect of wet screen sieve of aggregate. These conclusions proposed can be applied to determining the extent of damage of mass concrete due to the complex load and other environmental effects.