基于数值模拟的砂柱微生物注浆影响因素分析

Influencing factors of bio-grouting precipitation in sand column based on numerical simulation analysis

微生物注浆是一种较为新型的地基处理方式,其过程是一个复杂的物理化学生物过程,然而大量实验表明仅靠实验很难全面而系统地研究影响微生物注浆效果的主要因素。通过砂柱中微生物注浆过程的数值模拟,可以探究渗流传输与反应过程中各因素的影响作用,其影响主要体现在注浆结束后砂柱中碳酸钙的沉淀率和碳酸钙沿砂柱长度范围内的分布特征。本文首先通过已有实验数据与模拟结果的对比分析验证了一维数值模型的合理性,然后通过数值模型计算不同初始菌液酶活、营养盐浓度、营养盐传输速率和静置反应时间等因素作用下碳酸钙沉淀沿砂柱长度的分布变化和沉淀率,分析各影响因素对注浆过程的作用。结果表明初始酶活和营养盐传输速率是控制碳酸钙沉淀分布均匀性的重要因素,较小的尿素水解速率与较大的营养盐传输速率有利于碳酸钙的均匀沉淀,而适宜的营养盐浓度能够生成更多的碳酸钙沉淀,同时需要足够长的静置时间使砂柱中的营养盐完全反应。

Bio-grouting is a relatively new and innovative ground reinforcement method. However, it is hard to make a systematic and comprehensive research on the influencing factors by experiments because it is a complex physical and biochemical process. The 1D finite-element simulation method for the bio-grouting process in sand column is used to analyze the impact of several factors that influence on the distribution of calcium carbonate precipitation along the sand column and the precipitation rate after reaction. In this paper, the simulation results and the experimental ones are compared to validate the 1 D finite-element model. And then the factors affecting the bio-grouting process are analyzed by simulation results, including the initial enzyme activity, the grouting rate, the concentration of nutrient solution and the no-flow reaction time. The simulation results indicate that the initial enzyme activity and grouting rate have great influence on the homogeneity of the distribution of calcium carbonate. Appropriate nutrient concentration can contribute to more calcium carbonate precipitation and it will take a certain amount of time to finish the total precipitation.