圆柱孔破损膨胀土强度和变形特性的CT-三轴试验研究

Study of strength and deformation of cylindrical hole damaged expansive soil by CT-triaxial test

通过8组不同孔径破损膨胀土的CT-三轴试验,研究了圆柱孔破损重塑膨胀土的变形、强度特性以及破损结构的演化规律。试验结果表明:圆柱孔破损对膨胀土的强度有明显的弱化作用,但破损孔径大小的影响不大。吸力一定时,圆柱孔面积变化随着净围压的增加而减小;净围压相同时,吸力大的试样圆柱孔面积减少得越大。净围压在破损重塑膨胀土结构演化中发挥重要作用,随着净围压从50 kPa增加到200 kPa,CT图像的均值(ME值)提高幅度增大,试样内部的平均密度变大;相应地,CT图像的标准差(SD值)降低的幅度也增大,试样结构趋于均匀化。

The properties of deformation, strength and structural evolution of cylindrical hole damaged expansive soil are investigated by eight CT-triaxial tests. The results show that the strength of the samples with the cylindrical holes is significantly weakened because of the hole damage. Howerver, the hole size has little influence on the strength of the sample. The hole section area decreases when net confining pressure increases under a certain suction. The reduction of the hole section area is more obvious when the suction is larger under the same net confining pressure. Moreover, the net confining pressure plays an important role on the structural evolution of the cylindrical holes in the remolded expansive soils. The increment of the mean value （ME value） is enhanced gradually when the net confining pressure is changed from 50 kPa to 200 kPa. It means the sample becomes denser when the confining pressure is larger. Accordingly, the decrement of the standard deviation （SD value） increases gradually. The structure of the sample becomes homogenized during the test.