软土地区桩端后注浆失效补救方法及效果验证

Remedial method and effect verification for post-grouting failure at pile tip in soft soil area

通过上海软土地区某项目桩端后注浆失效时补救的实践,提出了一种桩侧成孔埋设注浆管进行后注浆补救的施工方法,该方法包括如下步骤:(1)尽量贴近既有桩基于桩侧对称成两个补救孔,成孔时应采用下钢套管的方式控制垂直度;(2)埋设两根注浆管,一根伸入桩底、端部有带逆止功能的注浆器,称为“补救注浆管”,采用约1.0 m长度隔离材料对“补救注浆管”进行包裹,避免封孔时“补救注浆管”被堵塞;另一根底部位于隔离段以上,桩底以上1.0 m,用于封孔,称为“封孔注浆管”;(3)通过“封孔注浆管”进行水泥-水玻璃双液注浆封孔;(4)待封孔48 h后,水泥-水玻璃双液注浆加固体达到一定强度,通过“补救注浆管”进行注浆,考虑到注浆的有效性,建议补救注浆的注浆量按原设计注浆量的两倍考虑。桩基静载荷试验结果显示,通过桩侧成孔补救注浆后,桩基的单桩竖向抗压承载力不低于正常注浆桩基的单桩竖向抗压承载力。

Based on the practice of remediation for the failure of post-grouting at the pile tip in a Shanghai soft soil area project,a method of post-grouting remedial construction was proposed,which involves embedding grouting pipes by forming holes at the pile side.The method includes the following steps:(1)Form two remedial holes symmetrically on the pile side as close as possible to the existing pile,controlling verticality by using steel casing during hole formation.(2)Embed two grouting pipes,one of which extends to the pile bottom and is equipped with a grouting device that includes a backstop function for grouting,referred to as the“remedial grouting pipe”.This pipe is wrapped with approximately 1.0 m of isolation material to avoid blockage during hole sealing.The other pipe is located above the isolation section and 1.0 m above the pile bottom for hole sealing,referred to as the“hole sealing grouting pipe”.(3)Seal the hole with a cement-water glass double liquid grouting through the“hole sealing grouting pipe”.(4)After the cement-water glass double liquid grouting reinforcement reaches a certain strength within 48 h,perform grouting through the“remedial grouting pipe”.Considering the effectiveness of grouting,it is recommended that the volume of remedial grouting should be considered as twice the original design grouting volume.The static load tests results of the pile foundation show that the vertical bearing capacity of a single pile of the remedial grouting pile foundation by forming holes at the pile side is not lower than that of a single pile of the normal grouting pile foundation.