似平面应力条件下混凝土的变形特性

Deformation properties of concrete under quasi plane stress sate

采用真三轴设备对100mm×100mm×100mm的立方体混凝土试块进行静态加载:1)保持3个轴向的应力相同,施加应力到试验设计值p;2)在保持最小主应力(Z轴)恒定,并且X轴应变速率与Y轴应变速率之比恒定的条件下,单调地增加Y轴应变.p的取值有三档,分别为10、15和20 MPa;每一档p对应的应变速率比的取值有三档或四档,在0.25、0.5、0.75和1.0中选取.分析试验曲线和数据可知:在加载过程的后半部分,Z轴应变和Y轴应变之间以及Z轴应变和X轴应变之间都近似呈线性关系,但是不同加载路径对应不同的拟合直线斜率.结合相关的微分方程可知,当最小主应力相同,加载应变速率比不同时,可以将Z轴应变分别对X轴和Y轴应变的微分关系回归出相同的数值,它们与破坏形态和剪切带倾角有关.

The specimens（cubes,d=100mm）were statically loaded into a true triaxial apparatus.1）The stresses in all three directions were simultaneously increased to a specified value of p.2）The strain in Yaxis was increased monotonically while maintaining a constant minimum principle stress in Z-axis as well as a constant strain rate ratio between the X-axis and the Y-axis.Three different values of p were chosen,which were 10,15 and 20MPa.Three or four strain rate ratios were chosen,which were 0.25,0.5,0.75 and 1.0,for each value of p.According to analysis of experimental data and curves,the following conclusions were obtained.In the latter part of loading process,relationship between Z-axial strain and Yaxial strain approximates to linear,as well as the relationship between Z-axial strain and X-axial strain,but the corresponding slopes of fitting lines are different with each other under different load paths.Comparing differential equations with fitting equations of curves,when the minimum principal stress is constant,the same numerical differentiation of Z-axial strain versus X-axial strain and Z-axial strain versus Y-axial strain are calculated for different strain rate ratios,which is related to failure modes and inclination of shear bands.