多层互剪搅拌桩工法的工艺因素模型试验研究

Model test study of key factors of deep soil mixing mechanism using contra-rotational shear method

采用模型试验方法,对多层互剪搅拌桩工法(contra-rotational shear deep soil mixing,简称CS-DSM工法)的工艺因素进行了试验研究,探索了水泥掺量、单位桩长搅拌次数T、单位体积搅拌能量E以及内外钻杆转速比RN等工艺因素对搅拌桩均匀性与强度UCS的影响。模型试验研究发现,通过多层互剪搅拌能够根除地表冒浆、防止糊钻抱钻、提高固化材料利用率。18组模型试验结果阐明搅拌桩在T-E-UCS之间存在固有关联,并揭示出机械参数、输出能量与桩身强度之间的本质关系。提供的计算方法可以定性指导选取合理的工艺参数,实现桩身设计强度目标。作为重要工艺因素,内外钻杆转速比RN与桩身强度试验曲线存在极值点,建议在工程中将1.80~2.20作为获取桩身峰值强度的最优RN值域。CS-DSM工法应用的系列研究结果为高质量搅拌桩工艺控制原则和质量保障体系提供了试验依据。

Small scale model test was conducted to investigate the technology factors related to contra-rotational shear deep soil mixing(CS-DSM)method,the effects of these factors,such as cement content,blade rotation number T,mixing energy E,rotation speed ratio of internal to external rod RN on the uniformity and unconfined compression strength(UCS)of the mixing pile were explored.The results show that the shearing motions of contra-rotational drilling tool can reduce excessive surface spoil and prevent entrained rotation phenomenon effectively,thereby greatly improve utilization of the binder material.The results of 18 model tests also reveal the inherent connection between T-E-UCS,and the internal relationship between machine operation parameters,mixing energy and strength of the piles.Construction parameters can be determined to ensure the target design strength by the provided calculation method.There is a peak value in the UCS-RN curve,an optimal range of RN=1.8−2.2 is recommended for achieving peak strength of piles in engineering application.The presented technical basis has set the cornerstone for the construction process control and quality assurance as well as quality control of CS-DSM method.