| 强震区黄土结构演变与力学响应机制 |
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| 引用本文： | 刘伟,孙欣然,何乃武.强震区黄土结构演变与力学响应机制[J].地球科学,2022,47(12):4442-4455. |
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| 作者姓名： | 刘伟 孙欣然 何乃武 |
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| 作者单位： | 1.内蒙古大学交通学院, 内蒙古呼和浩特 010070 |
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| 基金项目： | 内蒙古自治区自然基金项目2020BS04003国家重点研发计划项目2019YFC1509700国家自然科学基金42067066 |
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| 摘 要： | 黄土因其遇水产生湿陷变形而对工程构筑物的安全性造成严重威胁.强震区黄土遭遇先期地震后其内部结构将发生变化，结构演变与黄土初始含水量密切相关.先期地震对黄土的结构性破坏引起宏观力学特征变化，为揭示强震区黄土结构演变与力学响应的内在机制，基于动三轴对黄土试样预先施加不同PGA（peak ground acceleration）条件下动荷载进行预震处理，模拟强震区先期地震对黄土的扰动，后进行固结不排水试验，分析抗剪强度指标与地震荷载及初始含水量的关联性.试验结果表明，初始含水率为2%时，预先施加地震动荷载的黄土试样与未预先施加动荷载的试样相比，其峰值强度出现了明显降低，且随着预先施加动荷载PGA的增加，峰值强度降幅增加.孔隙水压力随应变的不断增加趋于平缓，有效轴向应力和有效围压随应变的不断增加而持续减小，最终趋于平缓；初始含水量增加至12%，预震处理后的黄土试样强度增大.通过绘制应力路径关系曲线，确定了强震区黄土失稳的临界失稳线，对于同一黄土试样，PGA增加后引起黄土失稳线不断下移，表明黄土中的应力状态随地震动荷载的增加而发生变化.初始含水量为12%时，预震后的黄土试样剪切强度增大，表明含水量增加后，前期地震荷载开始破坏黄土初始结构性，导致试样密度增大，产生强度增加效应.
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| 关 键 词： | 强震区 黄土 结构演变 强度劣化 临界失稳线 岩土工程 |
| 收稿时间： | 2022-06-30 |
Structural Evolution and Mechanical Response Mechanism of Loess in Strong Earthquake Area |
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| Abstract: | Loess poses a serious threat to the safety of engineering structures because of its collapsibility and deformation when it encounters water. The internal structure of loess in strong earthquake areas will change after encountering historical earthquakes, and the structural evolution is closely related to the initial water content of loess. Structural damage of loess by historical earthquakes also affects its macroscopic mechanical characteristics: In order to reveal the mechanism of the structural evolution and mechanical response of loess in strong earthquake areas, the loess samples were pre-seismically treated with dynamic loads under different PGA (peak ground acceleration) conditions via dynamic triaxial tests, so that the disturbance of historical earthquakes to loess was simulated. Afterwards, the undrained test was carried out to analyze the correlation between the shear strength parameters, the seismic load and initial water content. The test results show that when the initial moisture content is 2%, the peak strength of the loess sample with pre-seismical treatment is significantly lower than that of the sample without pre-seismical treatment, and with the increase of PGA, the peak strength decreases. The pore water pressure eventually tends to be constant with the continuous increase of the strain, the effective axial stress and the effective confining pressure decrease with the continuously increasing strain, and finally tend to be content. When the initial water content increased to 12%, the strength of the loess sample after pre-seismical treatment increased.By drawing the stress path relationship curve, the critical instability line and failure line of the loess in the strong earthquake area are determined. For the same loess samples, the increase of PGA causes the loess instability line to move down continuously, indicating that the stress state in the loess changes with the increase of the earthquake dynamic load. When the initial moisture content is 12%, the shear strength of the loess sample after pre-seismic treatment increases. |
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