为加快高含水率软土排水固结,运用氢氧化钙和阴离子型聚丙烯酰胺(APAM)处理上海某施工现场钻孔灌注桩的高含水率泥浆,并进行试验研究。通过一维固结试验揭示不同添加量下废浆孔隙比、固结系数和渗透系数随荷载的变化规律,确定氢氧化钙和APAM的最优添加量;并开展最优添加量下废浆的真空预压模型试验。结果表明:①一维固结试验中,氢氧化钙和APAM改良后废浆的固结系数和渗透系数均有较大提高,加快了废浆的排水固结速率;②同时,氢氧化钙和质量分数0.2%的APAM溶液的最优添加量约为0.8%和11.2%,超过最优添加量,废浆的固结系数和渗透系数均有所减小;③真空预压模型试验中,经氢氧化钙改良废浆固结系数明显提高,其平均径向固结系数分别为添加APAM溶液废浆与原状废浆的5.1,7.2倍,添加APAM溶液的废浆平均径向固结系数仅为原状废浆的1.4倍。因此氢氧化钙改良联合真空预压法能有效提高废浆排水固结速率。
Abstract
In an attempt to accelerate the drainage consolidation of soft soil of high water content, calcium hydroxide and anionic polyacrylamide (APAM) were mixed into the slurry of high water content in the borehole at a construction site in Shanghai. The optimum dosages of calcium hydroxide and APAM were determined according to the laws of slurry porosity, consolidation coefficient, and permeability coefficient varying with load obtained by one-dimensional oedometer test. Furthermore, vacuum preloading model test was conducted on the slurry modified with calcium hydroxide and APAM of optimum dosages. Results show that: (1) In one-dimensional oedometer test, the consolidation coefficient and permeability coefficient of modified waste slurry both increased, which accelerated the drainage consolidation. (2) In the meantime, the optimal dosage of calcium hydroxide and APAM solution with 0.2% mass fraction is about 0.8% and 11.2% mass fraction of the waste slurry, respectively. Beyond that optimum dosage, the consolidation coefficient and permeability coefficient both declined. (3) During vacuum preloading, the consolidation coefficient of waste slurry modified by calcium hydroxide increased evidently, with its average radial coefficient of consolidation 5.1 and 7.2 times of that modified by APAM and original slurry, respectively; the average radial coefficient of consolidation of the waste slurry conditioned with APAM is 1.4 times of that of the original waste slurry. In conclusion, the drainage consolidation of slurry can be effectively accelerated by adding calcium hydroxide combined with vacuum preloading.
关键词
高含水率泥浆 /
氢氧化钙 /
阴离子型聚丙烯酰胺 /
固结特性 /
微观结构
Key words
slurry with high water content /
calcium hydroxide /
APAM /
consolidation property /
microstructure
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