EVALUATION OF AIR BUBBLES DISTRIBUTED ON CONCRETE SURFACE OF SIDE WALL OF TUNNEL LINING

トンネル覆工コンクリートの側壁に生じる表面気泡量の評価に関する基礎研究

Marks of air bubble often occur on concrete surface of side wall in tunnel lining, because the sidewalls are generally constructed with greater slope than the right angle. In particular, the marks remained on the sidewall are likely to be noticeable from inspection sidewalks. It may negatively influence on aesthetic evaluation of the lining concrete. The ultimate purpose of the study is to reduce the air bubble, and to construct tunnel lining with high quality of concrete surface. For the objectives, the present study aims to develop an evaluation method of air bubbles on concrete surface at first. A photographic image and pressure-film methods were employed to quantify area ratio of the air bubbles. Also a concrete mold, simulated the sidewall form of tunnel linings(arch centre), was prepared. To examine the air bubbles, concretes were cast into the mold with various angles, such as 0(the right angles), 15, 30 and 45 degrees. The form materials were mild steel and ceramic-coated steel, both materials are generally employed in the arch centre. Marks of air bubbles on the hardened concrete were measured by using the both methods. The comparative result indicates that the pressure-film method can provide more appropriate evaluation than the photographic image method. In addition, area ratio and numbers of generated air bubbles were quantified by using the pressure-film method. According to the fundamental tests, the ceramic-coated steel form with 0 and 15 degrees is likely to generate air bubbles and the steel form with 15 degrees or greater has more air bubble distributions than the ceramic coat form.トンネル覆工コンクリートの側壁部には表面気泡が発生しやすく、且つ点検通路の目線位置にあるため、覆工コンクリートの出来映え(美観性)の評価に与える影響が大きい。そこで本研究では側壁部に生じる表面気泡の低減を目的とし、その基礎的検討として表面気泡の定量評価方法を考案した。特に、型枠材質および打設角度の影響を調べるため、覆工型枠(セントル)の側壁部を模擬した型枠内にコンクリートを打設し、表面気泡の発生状況を調べた。圧力測定フィルムを用いた画像解析により表面気泡面積や発生数を求めたところ、型枠の角度が15°以上では、セラミック塗装鋼板型枠よりも鋼型枠の方が表面気泡は発生しやすいことを示した。

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  • English
  • Japanese

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  • Accession Number: 01561301
  • Record Type: Publication
  • Source Agency: Japan Science and Technology Agency (JST)
  • Files: TRIS, JSTAGE
  • Created Date: Apr 23 2015 10:49AM