迅速な設置が可能な地盤比抵抗測定における打込み電極管の開発
打込み電極管の適用性と最近の開発状況
近年，地盤改良工事に対する要求項目や要求品質レベルの高度化に伴い，地盤改良体の出来形管理の重要性が高まりつつある。有力な出来形の確認手段として比抵抗トモグラフィによる方法が挙げられるが，施工時管理に適用するには電極設置の手間やコストが課題となっていた。本報では，迅速に電極設置が可能な方法として著者らが開発した打込み電極管の概要とその適用性を示す。さらに，最近の開発状況として新たに試作した高耐力多点電極管の概要と硬質地盤へグラウト注入を併用した方法による電極設置を想定した施工試験結果について述べる。その結果，グラウト強度を調整することにより硬質地盤に対しても打込み電極管による電極設置が可能であることが示された。今後，施工時管理としての比抵抗測定システムを完成させるべく検討を進めていく。
キーワード：打込み管，比抵抗測定，高耐力，地盤改良，施工管理
＊１ 技術センター 社会基盤技術研究部 地盤研究室
Development of Readily Installable Electrodes Mounted on the Driving-Pipes for Resistivity Measurements
Applicability of the Driving-Pipes and Latest Study
With a recent rise in demand for higher requirements and quality level of ground improvement work, it has become more important to verify the quality or shape of soil-improved bodies. Although resistivity tomography is one of the effective methods to verify the shape of improved bodies, it has its disadvantages including the extra work and cost of installing electrodes, which prevents seamless application to construction management. This paper describes the driving-pipe electrode, developed by the authors as a solution to realize readily installable electrodes, and its outline and applicability to resistivity tomography. In addition, some recent developments are described, which include the outline of a newly developed prototype high-strength multi-point electrode and the result of installation test assuming driving of electrodes into the grout injected into hard ground in advance. The results indicate that installing electrodes in the form of driven pipes is feasible even in hard ground by adjusting the grout strength. The authors plan to continue working on the resistivity measurement system to make it practically useful as a tool of construction management.
Keywords: driving-pipes, resistivity measurement, high strength, ground improvement, construction management
*1 Geotechnical Research Section, Infrastructure Technology Research Department, Taisei Advanced Center of Technology