地下鉄4線と送水管2本に並列近接したシールド施工と切羽での支障物撤去:国道479号　清水共同溝

摘要

Ine National Route 479 Shimizu Utility Tunnel Installation Works 4 was designated to construct a utility tunnel that houses electricity/water supply lines under National Route 479 using an EPB shield TBM.The tunnel is 1,343m in length and lined with segments with an outer diameter of Ø5.0m and inner diameter of Ø4.6m. The conditions of these shield works were:small cover of 6 to 10m(1.2-2D),probable existence of weak clayey ground of 0-2 in N-value,TBM driving close to important underground structures(four subway lines,two large water pipes,etc.)the whole way and removal of underground obstacles in compressed air.It was a great challenge to reduce the impact on the vicinity including nearby structures. This report contains information on measures for constructing close to important underground structures as well as construction results including work to remove obstacles in compressed air.%大阪市建設局発注の国道479号清水共同溝設置工事-4は，国道479号の地下に延長1,343m，セグメント外径Ø5.0m，仕上がり内径Ø4.6mの電気·水道共同溝を泥土圧シールド工法により構築するものである. 本シールド工事の特徴は，土かぶりが6～10m(1.2～2D)と小さいこと，掘削対象土層にN値0～2の軟弱粘性土層が含まれること，重要地下構造物(地下鉄営業線4本，大口径送水管2本など)と全線にわたり近接施工となること，圧気工法を用いた地中での支障物撤去作業があること，が挙げられ，近接構造物を含む周辺への影響低減が最大の課題となった. 本稿では，重要地下構造物の近接施工における対策工，ならびに圧気工法を用いた支障物撤去工を含む施工実績について報告する.