围压作用下混凝土的静动力细观破坏机理

为了解释围压作用下混凝土静、动力力学性能发生变化的物理机制，根据不同围压下混凝土的宏观破坏现象，通过研究知低围压下断裂力学适于混凝土强度的分析，而高围压下需要借助塑性力学工具.根据混凝土材料的细观结构，揭示了低围压作用下混凝土中微裂纹的开裂、扩展、串接直至破坏的细观损伤过程和破坏机理.利用线弹性断裂力学，考虑主控裂纹之间的相互作用，建立了低围压条件下混凝土静力强度的预测模型；利用断裂动力学，考虑裂纹扩展速度对其应力强度因子的影响，建立了低围压条件下混凝土动力强度的预测模型.理论模型的计算结果表明，加载速率影响围压作用下混凝土的抗压强度，加载速率越快混凝土动力抗压强度提高得越多，但随着围压增大，混凝土动力抗压强度增强系数减小，模型结果与宏观试验现象一致.

Static and dynamic meso-failure-mechanism of concrete under confined compression

Discussion of macro failure phenomena of concrete under different confined compressions showed that fracture mechanics is suitable for predicting the static and dynamic mechanical properties of concrete and explaining the strength change mechanism under lower confined compression, but it fails under higher confined compression while plastic mechanics is effective. According to the meso-material structure of concrete, the rules of development and linkage between microcracks in confined concrete were discussed. In terms of this damage process, the meso-failure mechanism of concrete under confined compression was investigated. Based on the micro fracture mechanics, the static strength model under lower confined compressions was put forward considering the influences of two dominating cracks. Based on the dynamic fracture mechanics, the dynamic strength of concrete under confined compression was established taking cracking velocities into account. Computing results showed that the proposed theoretical model can reflect the effect of confined compression on static and dynamic strength of concrete. Dynamic strength of confined concrete increases with the enhancement of loading rates, but the dynamic enhancement coefficient of strength decreases with the increase of confined compression.