内外套管组合沉管夯扩法在大厚度湿陷性黄土地基中的现场试验研究

Field test study on sinking ramming by combination of internal and external casing method in thick collapsible loess foundation

由传统技术改进而来的内外套管组合沉管夯扩法,是一种利用内外套管组合沉管成孔,加大成孔深度,再由重锤二次夯扩挤密的新技术,地基处理深度可达60m。结合具体的工程,对在大厚度湿陷性黄土地基中使用该方法成桩的桩长26,32,35m的灰土挤密桩和桩长20,32,36m的水泥土挤密桩进行现场试验研究,测得两种桩间土挤密系数均不小于0.93,桩体压实系数均不小于0.97,湿陷系数均小于0.015,满足规范要求;同时承载力也满足设计要求。

The sinking ramming by combination of internal and external casing method is obtained by improving traditional technology. It is a new technology that makes use of combination of internal and external casing to sink and form holes, enlarges the depth of hole formation, and then uses heavy hammer to compact by twice sinking and ramming. The depth of foundation treatment can reach 60 m. Combining with specific projects, field test study of lime-soil compaction pile length of 26, 32 and 35 m and cement-soil compaction pile length of 20, 32 and 36 m which formed by the above-mentioned method were carried out on thick collapsible loess foundation. The results show that the compaction coefficient of soil between piles is not less than 0.93, the compaction coefficient of pile body is not less than 0.97, the collapsibility coefficient is less than 0.015, which meets the requirements of specifications, and the bearing capacity also meets the design requirements.