Numerical Study on Delayed Failure of Gentle Sloping Ground
Numerical Study on Delayed Failure of Gentle Sloping Ground
复制标题
缓坡地基延迟破坏数值研究
DOI：
10.1007/978-3-031-11898-2_118
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Susumu Iai & Masyhur Irsyam
中科院分区：
文献类型：
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作者：
Tetsuo Tobita;Hitomi Onishi;Susumu Iai & Masyhur Irsyam
2018年印度尼西亚苏拉威西岛地震（Mw7.5）在1%至5%的非常平缓的斜坡上引发了大规模的流动滑坡。据报道，这场前所未有的灾难造成数千人伤亡和失踪。虽然流动的详细机制尚未推测，液化被确定为一个可能的嫌疑人。在本研究中，使用二维有限元方法，通过模拟30 m厚和200 m长的粉砂层交替的缓坡地面（坡角2°）的动力特性，记录的加速度作为输入运动，对这种流滑的原因进行了数值研究。通过改变位于饱和松散砂（5 m厚）顶部的粉土（5 m厚）的渗透率来模拟流动滑动。当粉土（ksill = 1 × 10- 6 m/s）的渗透率低于饱和松砂（ksand= 1 × 10- 4 m/s）时，粉砂界面以上的表层在地震结束后很长时间内开始流动。在1,000 s的模拟中，得到了约40 m的地面位移。通过对边界元的观测，发现粉土层中的超孔隙水压力逐渐增大，而液化层中的超孔隙水压力逐渐消散。这种破坏的机理被认为是液化过程中的孔隙重新分布或水膜的形成，这可能导致缓坡地基的延迟破坏。尽管这项研究成功地模拟了2D模型中的延迟破坏，但仍有进一步研究的空间来寻找印度尼西亚苏拉威西岛帕卢特定地区发生流滑的原因。
The 2018 Sulawesi, Indonesia, earthquake (Mw7.5) triggered massive flow slide on very gentle slopes of 1% to 5%. Thousands of casualties and missing persons were reported due to such unprecedented disaster. Although detailed mechanism of the flow has yet been speculative, liquefaction is identified as a possible suspect. In the present study, cause of such a flow slide is numerically investigated using a 2D finite element method by simulating the dynamic behavior of the 30 m thick and 200 m long gentle sloping ground (slope angle 2°) of alternating silt and sand layers with the recorded acceleration as an input motion. Flow slide was simulated by varying the permeability of silt (5 m thick) located on top of the saturated loose sand (5 m thick). When the permeability of silt (ksilt= 1 × 10–6m/s) is set lower than that of the saturated loose sand (ksand= 1 × 10–4m/s), the surface layer above the boundary between the silt and sand starts to flow long after the ground shaking ended. In total 1,000 s of simulation, the ground displacement of about 40 m was obtained. Close observation at the boundary elements revealed that the excess porewater pressure is gradually increasing in the silt layer while that in the liquefied layer dissipates. Mechanism of this type of failure has been studied as the void redistribution mechanism during liquefaction or the formation of water film, which may cause delayed failure of the gentle sloping ground. Although this study successfully simulates the delayed failure in 2D model, there is room for further research into seeking causes of the flow slides occurred in specific areas in Palu, Sulawesi, Indonesia.