换填与加筋结合处理路基加宽下软土地基的效果分析

针对软土地基上旧路加宽工程中不可避免的新旧路基间不均匀沉降问题，提出了换填一定厚度的软基并在路堤底部铺一层土工格栅的处理方法。采用有限元法对不加筋不换填、加筋不换填、加筋换填等几种路基加宽的软基处理方案分别进行了计算分析，得到以下结论：（1）换填与加筋相结合可明显降低软基上新旧路堤下地基的不均匀沉降AS；（2）当路堤高度和软基厚度一定时，△S随换填深度的增加或格栅抗拉模量的增大而减小，因此可以通过选择适当的换填深度和合适的格栅抗拉模量来达到控制不均匀沉降△S的目的。如果给定△S的容许值，则换填深度与格栅抗拉模量之间存在最佳组合，此时处理费用最低。提出了确定此最佳组合的方法；（3）当路堤高度不变而软基厚度过大时，或软基厚度不变而路堤高度过大时，即使换填深度达到经济最大深度（通常为3m），不均匀沉降AS仍会超过容许值，该处理方法不宜采用。

Study of Replacement Combining with Reinforcement to Treat Soft Ground under Widened Subgrade

To control the differential ground settlement between the old and the widened parts of subgrade on soft ground,a method that replacing a certain depth of soft soil with granular soil(such as sand,gravel,etc.) and placing a layer of geogrid at the base of embankment was proposed.The following measures to improve the soft ground were analyzed by FEM:(1)no improvement;(2)with reinforcement but without replacement;(3)with both reinforcement and replacement.Based on the numerical analysis,the following conclusio...