Earthquakes occur frequently in the Loess Plateau area, which result in damage to loess due to the disturbance of multiple cyclic loading. In this paper, the historical earthquake process is simulated by pre-dynamic loading treatment on undisturbed loess samples. Then cyclic tests are carried out on these treated samples to study the later liquefaction responses with different initial water content. The undisturbed sample is relative to the remold sample instead of the samples without disturbance. Results show that the axial deformation and pore pressure ratio of treated loess samples with initial water content of 5% are larger than those without treatment. For samples with initial water content of 10% and 15%, the cycle number required for liquefaction increases after treatment, but pore pressure ratio is between 0.18 and 0.36, which is less than the 5% water content samples. It means that liquefaction will have been formed before the excess pore pressure increases to large values. Combined with microstructural analysis, it is found that pre-dynamic treatment causes earthquake damage zone in loess with water content of 5%, which results in lower liquefaction stress ratio than non-treated ones. As for samples with water content of 10% and 15%, the internal voids become smaller and fine particles move into the gaps between large particles after treatment, resulting in denser structure which is hard to be liquefied. However, the increasing dynamic stress will aggravate the deterioration of loess at the water content from 5 to 15%. The changes of microstructure of loess samples are vulnerable to the dynamic stress amplitude and water sensitivity.

中文翻译：

---

前动力荷载对原状黄土动力液化的影响

黄土高原地区经常发生地震，由于多次循环荷载的干扰，导致黄土破坏。本文通过对原状黄土样品进行预动力荷载处理，模拟了历史地震过程。然后对这些处理过的样品进行循环测试，以研究不同初始水含量下的后期液化响应。未扰动的样品是相对于重塑的样品，而不是相对不受干扰的样品。结果表明，初始含水量为5％的处理过的黄土样品的轴向变形和孔隙压力比要大于未处理的样品。对于初始水含量为10％和15％的样品，液化所需的循环数在处理后会增加，但孔压比在0.18和0.36之间，少于5％水含量的样品。这意味着液化将在过量孔隙压力增加到较大值之前形成。结合微观结构分析，发现动力前处理引起黄土含水量为5％的地震破坏带，导致液化应力比低于未处理。对于含水量为10％和15％的样品，处理后内部空隙变小，细颗粒进入大颗粒之间的缝隙，导致结构致密，难以液化。但是，不断增加的动应力会加剧水含量从5％到15％时黄土的退化。黄土样品的微观结构变化容易受到动应力幅值和水敏感性的影响。这意味着液化将在过剩的孔隙压力增加到较大值之前形成。结合微观结构分析，发现动力前处理引起黄土含水量为5％的地震破坏带，导致液化应力比低于未处理。对于含水量为10％和15％的样品，处理后内部空隙变小，细颗粒进入大颗粒之间的缝隙，导致结构致密，难以液化。但是，不断增加的动应力会加剧水含量从5％到15％时黄土的退化。黄土样品微观结构的变化容易受到动应力幅值和水敏感性的影响。这意味着液化将在过剩的孔隙压力增加到较大值之前形成。结合微观结构分析，发现动力前处理引起黄土含水量为5％的地震破坏带，导致液化应力比低于未处理。对于含水量为10％和15％的样品，处理后内部空隙变小，细颗粒进入大颗粒之间的缝隙，导致结构致密，难以液化。但是，不断增加的动应力会加剧水含量从5％到15％时黄土的退化。黄土样品微观结构的变化容易受到动应力幅值和水敏感性的影响。