新近吹填淤泥地基真空固结失效原因分析及对策

新近吹填淤泥地基经无砂垫层真空预压技术加固后,土体强度增长有限,地基有效加固深度小,地基承载力仍然较低。为了深入分析新近吹填淤泥地基真空固结失效原因,首先对不同地区新近吹填淤泥的工程特性进行了系统地研究,然后采用3种典型的竖向排水体进行了室内真空固结单井模型对比试验研究,研究结果表明：①新近吹填淤泥中黏粒含量（d0.005 mm）过高、竖向排水体反滤层的等效孔径过小、真空加载速度过快是竖向排水体出现较严重淤堵现象的主要原因;②排水系统内的真空度局部损失较大,竖向排水体弯曲程度大和水平排水垫层中真空度传递阻力大均致使较大的真空度沿程损失;③土体中强亲水矿物含量较高、排水体中出现严重的淤堵现象和过大的真空度损失等共同降低了排水系统的排水效率,削弱了土体中的真空压力作用,最终致使土体的加固效果不理想。最后,有针对性地提出了相应的解决对策。

Causes and countermeasures for vacuum consolidation failure of newly-dredged mud foundation

For the newly-dredged mud foundation improved by the no-sand-cushion vacuum preloading technology (NSVPT), the soil strength increases only a little, the effective improved depth is small and the ground bearing capacity is still low. To analyze the causes, more comprehensive researches are made on the engineering properties of newly-dredged mud from different areas, and the comparative single-well model experiments with 3 kinds of representative vertical drains are conducted in laboratory using NSVPT. It is concluded: (1) the severe clogging problem in vertical drains is induced by high content fine-grained soils (d0.005 mm), too small characteristic opening size of filter (O₉₅) and too fast loading rate of vacuum preloading; (2) the partial loss of vacuum degree is great, and the friction loss of vacuum degree is also greatly caused by serious curvature of vertical drains and large transfer resistance of vacuum degree in horizontal drains; (3) the drainage efficiency of drainage system is reduced and the vacuum pressure in soils is weakened so as to mitigate the improvement effect of soils owing to high content of strongly hydrophilic minerals, severe clogging in vertical drains and large loss of vacuum degree. Accordingly, some countermeasures are put forward.