基于核磁共振的冻融循环作用下重塑黄土强度变化规律

为了研究冻融循环对重塑黄土抗剪强度的影响,分宏观及微观两个方面来进行试验研究。在宏观层面上,通过对不同冻融循环次数下、不同含水率的土样的进行三轴压缩试验,得到相应的应力-应变曲线;从微观层面上,利用核磁共振(nuclear magnetic resonance,NMR)成像分析仪,测得土样在不同冻融循环次数下的T_2时间分布曲线。结果表明:未冻融状态下,含水率为13%的土样其应力应变曲线为应变软化型;随含水率逐渐增加其应力-应变曲线由应变软化型变为应变硬化型。随冻融循环次数的增加,含水率为13%的土样其应力-应变曲线依旧为应变软化型;但抗剪强度逐渐降低,而随含水率逐渐增加,土样应力-应变曲线由应变硬化型有逐渐向应变软化型过渡的趋势;且含水率越高曲线软化趋势越明显。

The change law of reconstruction loess strength under the action of freeze-thaw cycle based on NMR

In order to study the effect of freeze-thaw cycle on the shear strength of reconstructed loess, this paper is divided into macroscopic and microscopic two aspects to carry out experimental research. In the macroscopic level, the corresponding stress-strain curves are obtained by the triaxial compression test of soil samples with different water content under different freezing and thawing cycles. In the microscopic level, the T2 time distribution curves of soil samples under different freezing and thawing cycles are measured by NMR imaging analyse. The results show that the stress-strain curve of soil samples with water content of 13% is strain softening type, which the stress-strain curve changes from strain softening type to strain hardening type. With the increase of freezing and thawing cycle, the stress and strain curve of soil samples with water content of 13% is still strain softening type. However, the shear strength decreases gradually. With the water content gradually increases, the soil sample stress and strain curve from the strain hardening type has the gradual transition to the strain softening type trend. The higher the moisture content curve softening trend is more obvious. The shear strength has a slow growth trend.