Publication Abstract

Proceedings of the Deep Mixing 2015 Conference, (DFI)

Development of Equipment for the Grid-Form Deep Mixing Walls in Areas Where Space Is Limited
Kazuo Konishi, Takenaka Civil Engineering & Construction Co., Ltd., Japan; Tatsuya Noguchi, Takenaka Civil Engineering & Construction Co., Ltd., Japan; Tadashi Chuman, The Estec Co., Ltd., Japan; Tetsuo Nasu, YBM Co., Ltd., Japan

After the Great East Japan Earthquake in March 2011, the demand for measures to deal with liquefaction in areas of detached housing, and for existing structures has been increased. The grid-form deep mixing walls (TOFT method®) are one such measure which has proved very reliable. Its effect in controlling liquefaction was proven in the 2011 Tohoku Earthquake and in the 1995 Kobe Earthquake1) 2), and the number of cases in which it has been used have increased steadily. However, since the method requires large equipment, it is difficult to apply it in areas of detached housing that are typically located in areas where space is limited. Furthermore, as the integrity of the grid wall is assumed to be important, there has been a concern that with conventional small equipment, a low stirring rod rigidity may fail to ensure sufficient vertical accuracy in construction, resulting in problems with integrity of the wall... In view of the above, small mechanical stirring equipment for the grid-form deep mixing walls (smart column method) was developed primarily for use with the TOFT method® in areas where space is limited. The equipment incorporates features to ensure sufficient vertical accuracy for columns for soil improvement. Cases of the application of the equipment reported include the first application of the TOFT method® to a new detached house, and an on-site quality test under actual ground conditions assuming application in an existing housing area in the coastal part of the Tokyo area. In both cases, the equipment provided improvement qualitatively equivalent to large equipment (in terms of strength, dispersion and vertical accuracy).

 article #2112; publication #1013 (DM-2015)