湿态混凝土抗压强度与本构关系的细观力学分析

采用细观断裂力学的方法研究湿态混凝土在外部荷载的作用下，裂纹及孔隙中水压力的大小和影响因素及其对混凝土受力性能的影响。根据湿态混凝土中裂纹的扩展规律，采用分枝型裂纹来研究湿态混凝土的抗压强度，利用能量等价原理来探讨湿态混凝土的本构关系和损伤特征。研究结果表明：（1）分枝型裂纹模型可较好地反映混凝土的体积变形和强度特征；（2）混凝土中的孔隙水压力减小阻碍混凝土开裂的摩阻力，因而加速混凝土的损伤和微裂纹的扩展；（3）与干燥态的混凝土相比，湿态混凝土的抗压强度降低，峰值应变减小，在同一应力水平下湿态混凝土的侧向变形增大。

MESOMECHANICS ANALYSIS OF COMPRESSIVE STRENGTH AND CONSTITUTIVE EQUATION OF WET CONCRETE

Mesomechanics analysis is adopted to analyze the effects of pore water pressure, which has close relation not only with the volumetric deformation of concrete, but also with the developing velocity of cracks, on the mechanical properties of wet concrete. In terms of the growth characteristics of cracks in the wet concrete and fracture mechanics, the wing crack model is employed to investigate the compressive strength and the stress-strain relation of wet concrete. The studies of constitutive equation and damage value of wet concrete are based on the energy equilibrium theory. The results of this investigation show that the wing crack model is suitable for describing the volumetric deformation and compressive strength of wet concrete. The free water in the cracks decreases the friction force, which baffles the development of cracks and accelerates the damage of wet concrete, decreasing the compressive strength of wet concrete compared with the dry sample. The critical compressive strain of wet concrete is smaller; but the lateral deformation of wet concrete is larger than that of dry concrete under the same stress level.