砂卵石地层重叠盾构隧道掘进加固方案比选研究

Comparison and Study of Reinforcement Measures for Overlapping Shield Tunnelling in Sandy Cobble Stratum

在重叠盾构隧道的掘进过程中,后建隧道施工不可避免地对地表及先建隧道产生一定影响,导致地表沉降、先建隧道结构发生变形,甚至影响结构安全,有必要对重叠盾构隧道掘进进行加固措施研究。当重叠盾构近接间距为强影响区时,为降低重叠隧道掘进相互影响,选取素混凝土桩、素混凝土桩+二次全周注浆、素混凝土桩+二次半周注浆及素混凝土桩+二次半周注浆+洞内钢支撑4种加固方案,依据地表隆沉及洞周收敛等评价指标进行判别,确定“素混凝土桩+二次注浆+洞内钢支撑”联合加固措施效果最佳,地表沉降最大值较未加固减少约38%,洞周收敛值可控制在3 mm内,满足施工控制要求。

In the excavation process of overlapping shield tunnels,the subsequent constructed tunnel will inevitably have a specific influence on the ground surface and the antecedent constructed tunnel,resulting in the surface settlement and deformation of the antecedent constructed tunnel structure and even affecting structural safety.Therefore,it is necessary to study the reinforcement measures of overlapping shield tunnelling.When overlapped shield tunnels locate closely in the strong impact area,in order to reduce the interaction of overlapped tunnelling,it selects and compares four types of reinforcement schemes,including plain concrete pile,plain concrete grouting pile+second full-perimeter grouting,plain concrete pile+second half-perimeter grouting and plain concrete pile+second half-perimeter grouting+steel brace inside tunnel.According to evaluation index such as surface settlement/heave and perimeter convergence,the combined reinforcement measures of"plain concrete pile+secondary grouting+steel support in the tunnel"show the best performance.The maximum surface settlement is reduced by approximately 38%compared with that without reinforcement,and the convergence value around the tunnel can be controlled within 3 mm,meeting the construction control requirements.