复杂应力状态下孔隙水压力对混凝土抗压强度的影响

Influence of Pore Water Pressure on Compressive Strength of Concrete under Complicated Stress States

将Terzaghi(太沙基)有效应力原理引入到饱和混凝土力学性质的研究中,探讨复杂受力环境下孔隙水压力对混凝土抗压强度的影响机制,建立了符合混凝土材料自身微结构特点的有效应力原理表达式,推导出三向一般应力状态下的孔隙水压力系数公式,用其预测不同围压下混凝土的抗压强度,并在应力空间压子午面内定量描述干燥混凝土及饱和混凝土基体真实应力加载路径的变化,所得到的趋势与试验结果相吻合.研究表明:孔隙水压力的存在改变了混凝土基体真实应力在应力空间的加载过程,从而改变了混凝土材料应力达到峰值时所对应的抗压强度;与干燥混凝土相比,准静态工况下饱和混凝土在各种应力状态下的抗压强度均有所降低,且受初始静水压力、孔隙率及加载路径的影响.从基体真实应力的角度揭示了复杂应力状态下孔隙水压力对饱和混凝土抗压强度的影响机理.

Terzaghi＇s effective stress principle was introduced to the study of the mechanical properties of saturated concrete,and the influence mechanism of water pressure in pore on the strength of concrete under complicated stress states was investigated.The expression of effective stress principle applicable to saturated concrete was established.The theoretical equation for the relationship between pore pressure increment and principal stress increment under general three-directional stress condition is proposed.By this model,the compressive strength of concrete under different confining pressures is predicted,and the variation of the matrix＇s true stress loading path between the saturated and dry concrete was quantitatively described in the compressive meridian planes of the principal stress space.Predicted trends are in good agreement with the experimental results.The results indicate that the existence of water pressure in pore changes the loading path of the matrix＇s true stress in the principal stress space.Therefore,the compressive strength when the stress state of the concrete reaches its limit is enhanced.The compressive strengths of saturated concrete in different stress states under quasi-static loading cases are decreased with the dry samples,which is influenced by the initial hydrostatic stress,pore ratio and loading path.The influence mechanism of the water pressure in pore on the strength of concrete can be interpreted from the viewpoint of matrix＇s true stress.