复合成孔灌注桩技术工程应用研究

Application of cast-in-situ pile technology with combined hole-forming

湿陷性黄土地基处理时,受到扬尘、噪音等环境治理的影响,挤密(灰)土桩、夯实水泥土桩等常规处理方法的应用逐渐受到限制。针对基底下分布有限厚度湿陷性黄土的工况,提出一种上部静压挤土、下部长螺旋取土复合成孔的灌注桩技术,将挤土密实效应和竖向增强作用有效结合,应用于湿陷性黄土地基的复合地基加固或桩基础。较常规湿陷性地基处理方法相比,该技术有较好的质量保证,施工中不易发生缩孔、断桩等问题。工程实践与现场试验分析表明,该技术适用于处理基底以下一定厚度的湿陷性黄土地基,亦适用于受扬尘、噪音等环境治理限制条件下的湿陷性地基处理工程,可为类似场地地基处理方案提供参考。同时对挤密桩间距的设计方法进行了分析,提出目标干密度的概念并应用于挤密桩间距的确定。

In the treatment of collapsible loess ground, the application of conventional treatment methods such as compacted soil(or lime-soil) piles and rammed cement-soil piles is gradually restricted due to the impact of environmental such as fugitive dust and construction noise. A combined hole-forming cast-in-situ technology which combines compacting effect and vertical reinforcement effect was developed to treat the collapsible ground with limited thickness. The effective combination of the compaction effect of the soil and the vertical reinforcement is applied to the composite foundation reinforcement or pile foundation of the collapsible loess foundation. Compared with conventional collapsible foundation treatment methods, this technology has better quality assurance. Problems such as shrinkage holes and broken piles are not easy to occur during construction. The results of engineering application and field test show that this technology is suitable for the treatment of collapsible loess foundations with a certain thickness below the base, and also for the treatment of collapsible foundations under the constraints of environmental control such as dust and noise. This work can provide a reference for the foundation treatment scheme of similar sites. The design method of the pile spacing is also discussed. The concept of target dry density is proposed and applied to determine the spacing of compacted piles.