原位置挿入型針貫入試験装置「T-GeoPenester®」の開発と適用
筆者らは，地盤改良における安全性・信頼性の高い施工の実現や品質不良のリスク低減に向けて，原位置にて多数の強度データを取得し，固化改良地盤の強度のばらつきを網羅的に把握する技術の開発にあたっている。これまで一軸圧縮強さquと相関があり，簡易に強度を把握できる「針貫入試験」を応用し，原位置の固化改良地盤内で多点測定を行う装置T-GeoPenesterを開発し実適用を進めてきた。今回，測定の更なる効率化・省人化を目指して吊下げ・制御装置および自動測定プログラムを新たに開発し，2つの地盤改良工事に適用した。現場測定では，全自動にて最大で115点の強度データを約2時間で取得でき，かつ取得データより換算したquが別途実施した一軸圧縮試験結果と整合したことから，開発装置による測定効率の向上と強度評価の実用性を確認した。
キーワード：改良土，針貫入試験，一軸圧縮試験，品質管理
＊１ 技術センター 社会基盤技術研究部 地盤研究室
Development and Application of In-situ Borehole Type Needle Penetration Test Apparatus, "T-GeoPenester"
The authors have been developing a technique to obtain a large number of strength data in situ and to comprehensively determine the strength variation of cement-improved soils with the aim of ensuring safe and reliable ground improvement and reducing the risk of quality defects. Building on the conventional needle penetration test, which can easily obtain strength correlated with unconfined compressive strength (UCS) qu, we have developed an apparatus called the T-GeoPenester. This device is capable of conducting in-situ multi-point strength measurements in cement-improved soils and has been applied in actual field implementations. This time, a new suspension/control device and an automatic measurement program were developed for more efficient and labor-saving measurement, and they were applied to in-situ needle penetration tests in the boreholes of cement improved soils at two construction sites. In the actual field measurement, it took only about 2 hours to obtain data from up to 115 measurement points using fully automated measurement. Additionally, the qu values derived from the obtained data corresponded well with the results of a separately conducted UCS test. Therefore, it was confirmed that the newly developed device and program can improve measurement efficiency and are applicable for practical strength evaluation.
Keywords: improved soil, needle penetration test, unconfined compression test, quality assessment
*1 Geotechnical Research Section, Infrastructure Technology Research Department, Taisei Advanced Center of Technology