中国における扁平大断面矩形状シールドの開発と試験施工: 寧波市地下鉄3号線引込み線

摘要

When constructing a subway in urban areas, there are major effects on the surrounding area using conventional cylindrical shield TBM. The test construction with the first rectangular shield TBM in China was implemented in order to minimize the effects on the vicinity. This test construction took place in conditions such as under small cover in weak and unstable sensitive clay, along alignment with both horizontal and vertical curves and using the flat large rectangular EPB shield TBM with an aspect ratio of 0.6.rnSufficient design and construction plans such as TBM and segments were considered in advance and efforts were made to carefully manage construction, to monitor signs of malfunction and to implement measures to them. As a result of test construction along a section of 100m in length, excavation went well with almost no tunnel deformation and little surface settlement. This report contains an outline of the process of development for the special rectangular shield TBM and test construction results.%市街地などに地下鉄を建設する場合，従来の円形シールド工法では周辺への影響度が大きく，周辺影響を最小化するために中国初の矩形状シールド工法の確立を目指し，試験工事を実施した.軟弱鋭敏粘性土地盤における小土かぶり，平面•縦断曲線の競合下という条件で，縦横比0.6の扁平大断面矩形状土圧シールドによる施工である.事前にマシン，セグメントなど十分な設計•施工計画を検討し，実施工では慎重な施工管理，不具合発生の兆候把握や対策施工に努めた.その結果，100mの施工区間ではあるが,トンネル変状もほぼなく，地盤沈下も少なく順調に掘進が行えた.ここでは，矩形状特殊シールドの開発経緯と試験工事結果について概要を報告する.