地中埋設物が水みちと土砂流出時の空洞形成に及ぼす影響  [in Japanese] Influence of buried structures on underground seepage and generation of cavities  [in Japanese]

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Abstract

都市部における道路陥没の主原因は,老朽埋設管破損部からの土砂流出による地中空洞形成であると考えられ,実際に陥没事故現場や地中空洞周辺には埋設物が存在することが多い。しかし,陥没や空洞周囲の埋設物に明確な破損部が確認できない事例もあり,土砂流出部のない埋設物付近で空洞形成や陥没発生が引き起こされる原因は不明である。本研究では,埋設物周囲で浸透流の集中箇所,「水みち」があり,土砂流出時には水みちを通して空洞が形成される,という仮説を立て検討を行った。地中埋設物周囲での水みちの様子と,埋設物の存在が土砂流出時空洞形成に与える影響を調べるため,定水位透水試験と小型土槽模型実験を実施した。定水位透水試験では地中埋設物と地盤境界部における透水性を,小型土槽模型実験では埋設物と浸透流の位置関係による空洞進展状況の違いを明らかにし,地中空洞周囲の密度低下領域「ゆるみ」は細粒分流出の他に,飽和度上昇と浸透力による変形に伴い引き起こされることを提案した。

Sinkhole accidents and depressions in urban areas are mainly caused by soil outflow through the breakage of sewer pipes. Underground cavities and loosened zones around those cavities are generated due to such soil outflow. However, some types of cavities are found to have developed close to underground structures, even though there has been no clear breakage in the structures. In this study, the influence of buried structures on the generation of cavities was investigated. A series of permeability tests was conducted to examine the local permeability of the soil at the boundary between the soil and a structure. It was suggested that the boundary between the soil and the structure had higher hydraulic conductivity than that of the ground. Model tests were also carried out to investigate the effects of buried structures on the expansion of cavities and ground deformation. It was revealed that the position of the underground structures strongly affects the generation of ground cavities. It was also observed that ground deformation expands before the expansion of cavities in sandy materials.

Journal

  • Japanese Geotechnical Journal

    Japanese Geotechnical Journal 10(1), 113-125, 2015

    The Japanese Geotechnical Society

Codes

  • NII Article ID (NAID)
    130005063954
  • Text Lang
    JPN
  • Data Source
    J-STAGE 
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