双轴压缩下混凝土预制双裂纹扩展与应力应变关系研究

Cracking and Stress-Strain Behavior of Concrete Containing Two Flaws under Biaxial Compression

对混凝土预制双裂隙板试件进行了双轴压缩试验,研究了裂隙倾角以及岩桥倾角对双裂隙的扩展演化影响。通过在裂隙尖端贴放应变片,分析了裂隙扩展与应力应变关系,探讨了裂隙尖端应变集中对裂隙扩展演化的作用规律。试验结果表明,裂隙倾角以及岩桥倾角对裂隙的扩展、贯通有较大影响。实验结果共观测到7种裂纹贯通模式(T1和T2;S1和S2;TS1、TS2和TS3)及两种贯通失败模式(剪切失败和拉伸-剪切失败),且随着岩桥角的增加,裂纹贯通模式由剪切裂纹贯通到翼型-剪切复合式贯通,然后再到翼形裂纹贯通逐渐转化。应力应变曲线与裂隙扩展贯通密切相关,拉应变集中是翼形裂纹产生的原因,而压应变集中则是引起剪切裂纹产生的原因。

The effects of flaw angle and rock bridge ligament angle on cracking behavior were investigated. The prismatic cement specimens containing two flaws were tested under biaxial compression. The relationships of stress-strain curve with cracking process are researched, and the influences of strain concentration at flaw tip on crack development are studied through the strain gauge. The experimental results show that the flaw parameters （flaw angle and ligament angle） have notable influence on crack development and coalescence process of the specimen containing two flaws. Seven patterns of crack coalescences （ T1 and T2 ; S1 and $2 ; and TS1, TS2 and TS3 ） and two failure patterns of crack coalescences （shear crack failure; wing-shear crack failure） are observed in the experiments. In addition, the crack coalescence varies from the S-mode to the TS-mode and then to the T-mode with the increase of ligament angle. The stress-strain curves of the specimens are closely related to the crack propagation. Tensile strain concentration may induce wing cracks, while compressive strain concentration will induce shear cracks.