APPLICATION OF LOCALIZED PIPE COOLING AS A COUNTERMEASURE TO PREVENT CRACKS IN TUNNEL CONCRETE LINING

覆工コンクリートひびわれ対策への部分パイプクーリングの適用

In the construction of the invert concrete, a section of the lining concrete experiences cracks caused by temperature contraction caused by the cement heat of hydration and the fluctuations of the outer temperature. The creation of these cracks affects durability. For this reason, in order to minimize the creation of these cracks, the authors proposed the “Localized Pipe Cooling” method. This method consists of placing cooling pipes only in the parts of the lining concrete experiencing high tensile stress. In the particular case of this study, the cooling pipes were placed in the lower-center part of the lining concrete. To confirm the mechanism of this method, three-dimensional FEM thermal stress analysis was performed. The localized pipe cooling method was applied to a real tunnel under construction. The application of this method was able to prevent the outbreak of penetration cracks. As a follow-up analysis, the authors measured the inner temperature and restriction distortion measured in blocks 1 to 4 of the concrete lining, confirming that the crack-outbrake probability dropped by more than 20%. インバートコンクリートを施工する区間の覆工コンクリートは,セメントの水和熱および外気温の変動による温度収縮がインバートに拘束され,貫通ひび割れの発生が懸念される.そのため著者らは,このような貫通ひび割れ対策として,引張応力の集中する側壁下部中央の範囲を限定的に短期間冷却することで引張応力の発生速度を緩和させる“部分パイプクーリング(Localized Pipe Cooling)”を提案した.さらに3次元FEM温度応力解析によりそのメカニズムを確認し,実施工への適用指標をまとめた. また,部分パイプクーリングを実施工に適用し,測定した内部温度および拘束ひずみを取り込んだ事後解析にて,ひび割れ発生確率が20%以上低減したことを確認した.これらの結果,有害なひび割れの発生を防止できた.

Language

  • English
  • Japanese

Media Info

Subject/Index Terms

Filing Info

  • Accession Number: 01633700
  • Record Type: Publication
  • Source Agency: Japan Science and Technology Agency (JST)
  • Files: TRIS, JSTAGE
  • Created Date: Feb 25 2017 3:24PM