三轴循环荷载作用下混凝土的力学性能及损伤特征研究

Study on Mechanical Properties and Damage Characteristics of Concrete Under Triaxial Cyclic Loading

开展了不同循环加卸载(荷载分别为单轴抗压强度20%、30%、40%、50%、60%、70%和80%)作用下的三轴试验,研究了不同循环荷载作用对灌注桩混凝土力学性能的影响,并分析了混凝土的损伤特征。结果表明:在各级循环加卸载作用下,混凝土的应力-应变曲线出现内凹和右移推进现象;弹性模量随循环次数的增加先增加后减小;在各级循环内,泊松比呈“减小-稳定-增大”的变化规律,第90次循环后超过名义泊松比,混凝土损伤逐渐积累加深,轴向和横向不可逆应变均随循环次数的增加而增加;屈服阶段前混凝土的累计损伤小,屈服阶段后混凝土的横向累计损伤参数比轴向大。

Triaxial tests were carried out under different cyclic loading and unloading(loads were 20%,30%,40%,50%,60%,70%and 80%of the uniaxial compressive strength),and the effects of different cyclic loads on the mechanical properties of cast-in-place pile concrete were studied,and the damage characteristics of the concrete were analyzed.The results show that the stress-strain curves of concrete specimens appear concave and right shift in the cyclic loading and unloading conditions at all levels.The elastic modulus first increases and then decreases with the increase of the number of cycles.The internal Poisson′s ratio of each cycle shows a change law of"decreasing-stabilizing-increasing".After the 90th cycles,it exceeds the nominal Poisson′s ratio and the concrete damage gradually accumulates and deepens.The axial and transverse irreversible strains increase with the increase of the number of cycles.The concrete cumulative damage before the yield stage is small,and the cumulative damage parameters after the yield stage are larger than those in the axial direction.