混凝土含损伤的摩尔-库伦强度模型试验研究

Experimental study on Mohr-Coulomb model with damage for concrete

对100mm×100mm×100mm立方体混凝土试块,利用真三轴设备,在平面应变条件下进行静态加载试验.试验数据表明,在压剪破坏条件下,混凝土材料的峰值强度和残余强度都遵守摩尔-库伦强度准则,残余强度的内摩擦角高于峰值强度的内摩擦角,残余强度的内聚力低于峰值强度的内聚力.进一步分析认为,混凝土的抗剪切承载能力包含内摩擦力和等效内聚力,在到达峰值点和过了峰值点之后,实际内摩擦力达到残余强度公式的计算值;混凝土的等效内聚力随着剪切变形的增加逐渐衰减,即使在测量强度的加载过程也是如此;对应于峰值强度线与残余强度线的交点,存在一个大小轴平均应力临界值,在保持大小轴平均应力恒定的条件下进行加载,如果所述平均应力小于该临界值,则剪应力-剪应变关系曲线出现下降段,如果大于该值,则不出现下降段.

By using a true triaxial apparatus, static loading experiments were conducted on 100 mm × 100 mm × 100 mm cubic samples of concrete under plane strain condition. It is found that in the case of compression-shear failure, both peak strength and residual strength of concrete abide by Mohr- Coulomb criterion, and peak strength has greater internal friction angle and less cohesion value compared with residual strength. Further analysis obtained the following conclusions. The Shear bearing capacity of concrete is composed of internal friction and equivalent cohesion. During the loading at and after peak point, actual internal friction equals to the calculated value drawn from residual strength formula. Before reaching the peak point, actual internal friction is less than the value from the same formula. The equivalent cohesion of concrete decreases with increase of shear deformation, and so does it even in the loading process for measuring strength. We name a two axial mean stress （TAMS） to represent the average value of maximum principal stress σ1 and minimum principal stress σ3, and then Mohr-Coulomb strength criterion can be expressed as a linear relation between shearing strength and TAMS. There exists a critical value of TAMS corresponding to the intersection point of peak strength line and residual strength line. During the loading process, if TAMS remains constant and less than the critical value, there will be a declining section in shear stress and shear strain relation curve. On the contrary, if it remains constant and larger than the critical value, there will be no declining section in this curve.