THE APPLICABILITY OF GROUTING METHOD FOR CRACKS OF RC OPEN CHANNEL SIDE WALL CAUSED BY FROST DAMAGE DETERIORATION AND THE EVALUATION OF FILLING RANGE USING ULTRASONIC METHOD

Abstract

The grouting method is widely applied to repair cracks in concrete structures, and sections treated with filling grout are generally checked by observing grout leakage from a different hole injected with the material. However, with the grouting method, areal spread in the filled section cannot be checked quantitatively, meaning that checking is limited to assumptions based on the intervals between pieces of grouting equipment. Meanwhile, the thin-walled structures characteristic of RC (reinforced concrete) open channel in cold snowy regions often sustain layered cracks requiring repair inside the structure as a result of frost damage deterioration. However, as only collected core specimens are examined for layered cracks, the continuity of cracking inside the structure remains unclear. In this study, the continuous occurrence of cracks was clarified through observation of cross sections from cut pieces of actual structures in order to check how layered cracks form inside the L-shaped block of an RC open channel which deteriorated by frost damage. It was also confirmed that consecutive layered cracks could be repaired by inserting grout using the grouting method because the appearance of such cracks is consecutive rather than discontinuous. It was shown that when an L-shaped block with layered cracks was confirmed with filling grout using the grouting method, the ultrasonic propagation velocity was likely be higher than before the treatment was applied. The study also revealed that the evaluation of whether or not layered cracks closed by filling grout could be done by focusing on transition of ultrasonic propagation velocity.注入工法は、コンクリートのひび割れ補修工法として広く用いられている。本研究では、まず凍害劣化の進行しているRC開水路のL型ブロックの部材内部に生じている層状ひび割れの発生形態を確認するために、実際に切断した断面を観察することで、層状ひび割れが連続して生じていることを明らかにした。連続している層状ひび割れは、注入工法によって注入材の充填を行うことが可能であることも確認した。また、層状ひび割れの生じているL型ブロックに対して注入工法による注入材の充填を行い、充填前後の超音波伝播速度の測定を行うことで注入材の充填部の把握が可能であることを明らかにした。