地震诱发石碑塬黄土地层液化滑移距离研究

Slippage Distance of Loess Deposit Triggered by Earthquake-induced Liquefaction in Shibeiyuan Area

摘要:

为研究1920年海原地震中石碑塬地区液化滑移灾害的形成机制、滑移特征及滑移距离，对石碑塬液化滑移区进行钻孔勘探、取样以及探槽开挖。分别对钻孔及所取试样进行剪切波速测试及颗粒分析、室内动三轴试验，得出石碑塬液化滑移区地层分布情况、震时液化土体层位以及不同地震烈度条件下砂质黄土层的液化情况。综合分析钻孔勘探、颗粒分析、动三轴试验结果，揭示出海原地震中石碑塬黄土地层液化滑移灾害的形成机制：砂质黄土层液化后在自重应力以及地震力的共同作用下"托浮"第一古土壤层以及上部"粉尘化"的非饱和黄土层沿缓斜坡运动，并利用液化滑移地层滑距公式对滑移距离进行估算，得到结果为223.35 m，与实际情况较为相符。研究结果可为黄土地层液化滑移灾害的预防提供一定的借鉴意义。

Abstract:

To study the formation mechanism, slip characteristics, and sliding distance of the liquefaction-induced slip disaster in the Shibeiyuan area during the 1920 Haiyuan earthquake, drilling exploration, sampling, and trench excavation were conducted in the Shibeiyuan liquefaction and slip area. Shear wave velocity tests, particle analysis, and indoor dynamic triaxial tests were performed on boreholes and samples. The stratum distribution in the liquefied slip zone of Shibeiyuan area, the layer of liquefied soil during the earthquake, and the sand under different seismic intensities were then obtained. The comprehensive analysis results of drilling exploration, particle analysis, and dynamic triaxial test revealed the formation mechanism of liquefaction-induced slip disaster of the loess deposit in Shibeiyuan area during the Haiyuan earthquake. The liquefied sandy loess layer floated the first paleosol layer and the upper "dusting" unsaturated loess layer to move along the gentle slope under the combined action of its own weight stress and seismic force. The slip distance formula of the liquefied slip deposit was used to estimate the slip distance (i.e., 223.35 m), which is consistent with the actual situation. The results of this research provide a reference for the prevention of liquefaction and slip disasters in the loess deposit.