The GEOASIA Research Society

2015

Analysis of the destruction of an embankment in the 2007 Noto Peninsula Earthquake

2007年能登半島地震において、宅地盛土や道路盛土の崩壊が多く発生し、地域住民に甚大な被害を与えた。盛土崩壊は地震中にすべて生じるのではなく、地震中は安定を保ちながらも地震後に時間遅れで生じた崩壊が、特に傾斜地盤上の盛土で報告されている。
そこで、崩壊現場から採取した土試料の力学試験結果をもとに、材料定数などの各種パラメータを同定した後、盛土崩壊挙動を数値解析的に再現するとともに、盛土崩壊メカニズムを調べた。




Analysis of the seismic response of a foundation ground improved by the sand compaction pile (SCP)

未改良中間土地盤とSCP打設による改良地盤の地震時挙動の比較解析を実施した。平面ひずみ条件ではあるが、砂杭打設時の周辺地盤の密度増加と砂杭への応力集中が寄与して、改良地盤は未処理地盤に比べて圧倒的に変形量が小さくなることがわかり、SCP改良効果が明らかとなった。



Analysis of the behaviour of a foundation-embankment coupled system, based on an experiment using a centrifugal loading model

Reports of damage to embankments from earthquakes are frequent, but the state of the damage is likely to vary depending on the conditions in the embankment and in the foundation beneath. With this in mind, a numerical analytic investigation was conducted of differences in seismic and post-seismic deformation behavior depending on initial variations in the firmness (density) of the foundation and embankment.

The results showed that: ① where the foundation and embankment were both firm, stability was maintained both during and after the quake, with only small amounts of deformation; ② where the foundation was firm but the embankment soft, there was a concentration of deformation in the embankment, resulting in considerable lateral swelling; ③ where the embankment was firm but the foundation soft, stability was preserved during the quake, but damage from circular slip occurred afterwards.




  1. Noda, A., Nakai, K. and Asaoka, A. (2008): Consolidation of clay and compaction/liquefaction of sand - A structure theoretic approach -, Theoretical and Applied Mechanics JAPAN, Vol.57, pp.41-47.





3-dimensional analysis・・・effect on ground settlement.

深層混合処理工法を用いた壁で四角に囲った改良体を離散的に配置した場合の砂質地盤の地震中および地震後挙動について、3次元解析を実施した。
改良ブロック体を配置した地盤部では、地震中の過剰間隙水圧の上昇が抑えられるとともに、その消散が早く、離散的に設置した場合についてもある程度の沈下抑制効果があることが明らかとなった。



Seismic stability assessment of a temporary structure on a soft foundation

砂と粘土の互層からなる軟弱な水平堆積地盤上に設置された仮設構造物の地震時安定性を調べた。
解析結果から、①仮設構造物のように不安定な構造物は、(大地震の場合には)砂層の液状化が原因となって転倒する危険性が高くなること、②転倒防止策としては、高さを低く、幅を広くすることが考えられるが、構造物自身の幅を広げなくても、敷設板の設置が有効であること、などが明らかとなった。



The nature of the transition “from deformation to destruction”

Using the example of a classic bearing force problem, an analysis was performed on the assumption that deformation and destruction do not need to be viewed as separate phenomena, but that destruction can be taken as the end stage of a path of deformation. The results clearly: ① reproduced phenomena such as the progressive onset of an obvious circular slip line with the increase of the displacement control load on the structure foundation, and then the fall off in load (load softening) that followed; ② showed that differences in initial conditions such as the state and the initial irregularities of the soil, or the presence or absence of friction in the load, have an influence on the ultimate load and on the destruction state.




  1. Noda,T., Asaoka, A. and Yamda, S. (2007): Some bearing capacity characteristics of a structured naturally deposited clay soil. Soils & Foundations, Vol.47, No.2, pp.285-301.
    平成19年度地盤工学会論文賞受賞論文


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