不同围压及加载速率下的塑性混凝土动力特性研究

Research on dynamic characteristics of plastic concrete under different confining pressure and loading rate

为研究塑性混凝土在三向应力状态下的动力特性与破坏规律,设计符合工程实践的配合比方案,借助动三轴试验仪开展了其在不同围压和不同加载速率条件下的强度、应力及应变规律研究。最后依据试验成果建立了基于Bresler-Pister三参数的强度准则。结果表明:塑性混凝土抗压强度与加载速率呈近线性正相关,材料抗压强度小于5.0MPa时对低加载速率更敏感,抗压强度大于5.0MPa时对高加载速率更敏感;不同加载速率下材料应力-应变规律基本一致,当应变达到1.47%~1.90%后其应力出现峰值,随后大幅度降低;不同围压条件下塑性混凝土抗压强度随围压的增加同样呈线性增长趋势,随着围压的提高,塑性混凝土峰值应力维持时间越长,材料抗裂性能越好;基于Bresler-Pister的强度准则公式其计算剪应力与三轴实测误差在1.61%~4.35%之间,基本反映了材料的变形破坏规律。

In order to study the dynamic characteristics and failure law of plastic concrete under three⁃dimensional stress state,the mix proportion scheme in line with engineering practice was designed,and the strength,stress and strain laws of plastic concrete under different confining pressures and different loading rates were studied by means of dynamic triaxial tester.Finally,the strength criterion based on three parameters was established according to the test results.The results show that the compressive strength of plastic concrete is nearly linearly positively correlated with the loading rate.When the compressive strength of the material is less than 5.0 MPa,it is more sensitive to the low loading rate.When the compressive strength is greater than 5.0 MPa,it is more sensitive to the high loading rate.The stress⁃strain law of the material under different loading rates is basically the same.When the strain reaches 1.47%~1.90%,the stress peaks and then decreases greatly.Under different confining pressure conditions,the compressive strength of plastic concrete also shows a linear growth trend with the increase of confining pressure.With the increase of confining pressure,the longer the peak stress of plastic concrete is maintained,the better the crack resistance of the material is.Based on the strength criterion formula of Bresler⁃Pister,the error between the calculated shear stress and the triaxial test is between 1.61%and 4.35%,which basically reflects the deformation and failure law of the material.