LANDSLIDES DURING THE EARTHQUAKES ON MAY 26 AND JULY 26, 2003 IN MIYAGI, JAPAN

LANDSLIDES DURING THE EARTHQUAKES ON MAY 26 AND JULY 26, 2003 IN MIYAGI, JAPAN
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DOI：
10.3208/sandf.45.4_149
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发表时间：
2005-08
期刊：
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影响因子：
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通讯作者：
渦岡 良介;仙頭 紀明;風間 基樹;海野 寿康
渦岡 良介;仙頭 紀明;風間 基樹;海野 寿康
中科院分区：
其他
文献类型：
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作者：
渦岡 良介;仙頭 紀明;風間 基樹;海野 寿康

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摘要我们对2003年5月26日地震中的筑馆町立下滑坡和2003年7月26日地震中的迦南町西砂留田滑坡进行了现场调查。此外，我们还研究了土壤的物理和力学性质，并进行了初步的数值模拟。大特什塔滑坡缓倾斜7°左右的缓坡地下土为火山碎屑堆积物。填土结构非常松散，但非饱和土在高吸力下保持稳定。滑坡发生在地震的主要运动期间或之后。滑坡体表现为泥石流。在循环剪切作用下，湿陷土易于液化。很可能是饱和填土在地震中液化。在地震作用下，非饱和填土在循环剪切过程中可能发生液化，失去初始抗剪强度。与Dateshita滑坡具有相似震级和结构的Nishisaruta滑坡发生在主震主运动后几分钟。降雨是加剧西沙鲁塔滑坡的一个重要特征，而在Dateshita滑坡之前的一周内没有观察到降雨。西砂留田滑坡的斜坡地下土是由细级配砂组成的填土，其来源于山上的砂岩。边坡上部因液化而丧失抗剪强度的部分沿边坡沿着向下，并以高含水量向下部稻田扩散。数值模拟表明，饱和填充液化期间的主震。前震产生的残余超静孔隙压力影响了边坡的稳定性。
ABSTRACT We conducted a site investigation for two major landslides : Dateshita landslide, Tsukidate-cho during the earthquake on May 26, 2003; and Nishisaruta landslide, Kanan-cho during the earthquake on July 26, 2003. In addition, we examined physical and mechanical soil properties and performed preliminary numerical simulations. The subsurface soil of the gentle slope of Dateshita landslide with an angle of about 7° was a fill with pyroclastic sediments. The structure of the fill was very loose, but the unsaturated soil remained stable with high suction. The landslide occurred during or immediately after the principle motion of the earthquake. The slide mass behaved as a mudflow. Then the collapsed soil easily fluidized with cyclic shear. It is likely that the saturated fill liquefied during the earthquake. Moreover, it is possible that the unsaturated fill fluidized, losing the initial shear strength during cyclic shear induced by the earthquake. The Nishisaruta landslide with similar magnitude and configuration to the Dateshita landslide occurred a few minutes after the principle motion of the main shock. Rainfall was an important feature that exacerbated the Nishisaruta landslide, whereas no rainfall had been observed for a week before the Dateshita landslide. The subsurface soil of slope of the Nishisaruta landslide was a fill with fine-graded sand, which originated from sandstone on the hill. The upper portion of the slope that lost shear strength because of liquefaction descended along the slope, and spread with high water content on the lower rice field. Numerical simulations have suggested that the saturated fill liquefied during the main shock. Residual excess pore pressure induced by the foreshock affected the slope's stability.