双向动荷载下重塑红黏土动变形特性研究

Dynamic Deformation Characteristics of Remolded RedClay Under Bi-directional Dynamic Load

摘要:

利用SDT-20型三轴仪探究双向动荷载下红黏土动变形特性。结果表明：相位差为0其他条件相同时红黏土动剪切模量随径向动荷载幅值增加而减小；双向动荷载下红黏土动剪应变与振动次数近似呈指数型关系增长，并存在一个临界循环次数；随含水率升高和固结应力增大，重塑红黏土破坏模式由受拉破坏变为受压破坏；径向动荷载幅值的增加使重塑红黏土更容易发生受拉破坏；双向动荷载下阻尼比随动剪应变增加无明显规律，动剪应变小于1%时阻尼比的变化无规律，动剪应变大于1%时随动剪应变增加阻尼比处于稳定平衡阶段。含水率对阻尼比变化规律有明显影响，含水率小于20%时阻尼比随含水率增大而增大，含水率大于20%时其对阻尼比影响可以忽略。

Abstract:

The dynamic shear modulus and damping ratio are important parameters for describing the dynamic characteristics of the soil. In this study, the dynamic deformation characteristics of red clay under bi-directional dynamic load was investigated by using a SDT-20 dynamic triaxial apparatus. The impact of moisture content, consolidation stress, consolidation ratio, and radial dynamic load amplitude, on the dynamic deformation characteristics of red clay, such as the hysteresis loop, dynamic shear modulus, dynamic stress-strain relationship, and damping ratio, were analyzed. The experimental results show that when the phase difference was 0 and all other conditions were the same, the dynamic shear modulus of the red clay decreased with the increase of radial dynamic load amplitude. The relationship between the dynamic shear strain of the red clay and vibration frequency was approximately demonstrated by an exponential function under a bi-directional dynamic load, and there was a critical cycle number Ndc. With the increase of moisture content and consolidation stress, the failure mode of red clay changed from tensile damage to compression damage. Tensile damage was more likely to happen with the increase of radial dynamic load amplitude. The change of the damping ratio did not present a certain rule with the increase of dynamic shear strain under bi-directional dynamic loading. When the dynamic shear strain was less than 1%, there was no regular pattern in the change of the damping ratio, while the dynamic shear strain was more than 1%, and the damping ratio was stable with the increase of dynamic shear strain. The radial dynamic load amplitude had no obvious impact; however, the moisture content had an effect on the damping ratio. When the moisture content was less than 20%, the damping ratio increased with the increase of moisture content; while the moisture content was more than 20%, its influence on the damping ratio was negligible. This study could be used as a reference for the further design of dynamic deformation characteristics and numerical calculation.