真空联合堆载预压处理深厚软基试验和数值分析

Experimental and numerical study of thick soft ground improved by vacuum-surcharge preloading

为提高深厚软基的深层加固效果,对某高速公路软基采用真空联合堆载预压法处理,改进了竖向排水通道形式.在试验路段中分别设置150 mm宽的塑料排水板和插入100 mm袋装砂井作为新型竖向排水体,其中细管长度10 m,直径8 mm,对比验证了两种新型竖向排水体在提高深厚软弱土层排水固结的功效.结果表明:150 mm宽塑料排水板内真空度衰减较少,预压期地基沉降量大,8 mm细管可增大袋装砂井中真空压力的传递深度.在修正剑桥模型的基础上,考虑了软土的流变性以及卸载后再加载的变形特性,改进土体本构模型,提出了相应的真空预压有限元数值计算方法.实例验算表明:计算值与实测值的数据大小及其变化规律都吻合较好.

To improve the deep strengthening effect,vacuum surcharge preloading method was applied in expressway to change the form of vertical drainage channel.150 mm width prefabricated vertical drain（PVD） and 100 mm modified bag sand-well were used respectively as vertical drainage body.The bag sand-well was inserted with 10 m long and 8 mm in diameter plastic small tube.The strengthening efficiencies of the two new drainage bodies for deep soft soil were verified by comparison experiments.The results show that attenuation of vacuum pressure is small in 150 mm width PVD with large settlement in preloading period,while the vacuum pressure transmit depth can be increased in 8 mm diameter plastic tube.Based on modified Cambridge model,the soil rheology and reload deformation characteristics after unload were considered to improve the constitutive soil model,and to propose corresponding finite element calculate method.The actual example validation indicates that the data fine accuracy and regularity of calculate values are consistent with those of test values.