基坑爆破预留层对围护桩的保护作用数值分析

基坑爆破开挖工程中爆破开挖部分与围护桩之间通常会预留一定厚度的岩土层,用以保护基坑围护结构的安全,免受爆破产生的巨大能量的损害。为了得到合理的预留层厚度,保证基坑开挖过程的安全,最大限度缩减施工周期,提高经济效益,采用LS-DYNA有限元分析软件,对基坑爆破开挖时对临近钻孔灌注桩的保护效果进行了数值计算分析。分析得出,预留1.5m厚中风化泥岩作为临近钻孔灌注桩的保护层,能显著降低爆炸荷载作用下钻孔灌注桩的压力峰值和最大主应力峰值,保护临近钻孔灌注桩免遭破坏;同时临近钻孔灌注桩的最后一排炮孔孔间采用25ms延时时间,可有效避免应力波峰值的叠加,进一步保护了钻孔灌注桩的安全。此结论可为类似工程提供参考。

Numerical calculation of the barrier effect of the pre-protective layer on bored piles in deep foundation pit blasting

In excavation engineering of foundation pit,the excavation part of blasting excavation is usually reserved for a certain thickness of rock layer to protect the safety of the surrounding structure of the foundation pit to avoid the great energy caused by blasting.It is not only to ensure the safety of foundation pit excavation process,but also to reduce the construction period and improve the economic benefit.The protection effect of the adjacent bored piles is analyzed by using LS-DYNA finite element analysis software.The analysis results showed that the protective layer of the weathered stone of 1.5 mthick,as adjacent bored piles,can significantly reduce the pressure peak and maximum principal stress peak of bored piles under explosive load,and protect adjacent bored piles from destruction.At the same time,the last of the holes in the drilled pile has a 25 ms deferring to prevent the stacking of the stress peaks,which will further protect the safety of the drilled pile.The conclusion can be used as a reference.