Numerical simulation on settlement characteristics and treatment of pavement structure on soft foundation

When building a highway on a soft soil foundation, problems such as excessive settlement and uneven settlement will be encountered, which will directly affect the flatness of the pavement, horizontal drainage, and driving comfort, increase the stress of the pavement structure layer, and lead to early damage of the pavement. Based on the soil consolidation theory, the settlement of four different pavement structures on soft soil foundation is simulated by the finite element method, and the influence of geogrid and CFG pile treatment on the settlement characteristics is studied. The research shows that the four different pavement structures with the same thickness have similar long-term settlement, the initial settlement is faster, and the following settlement speed is slower. Fifteen years after completion, the differential settlement of the pavement surface reaches 1.4 cm. Increasing the elastic modulus of the subbase has little effect on the settlement. The thickness of the base course should be controlled within a reasonable range, and the thickness of the appropriate graded gravel layer should be controlled within 12 to 18 cm. The simulation of ground reinforcement indicates that using a geogrid alone has minimal effect on reducing settlement in soft soil foundations. However, after adding CFG pile groups, the settlement at completion and after 15 years is significantly reduced, with minimal differential settlement, effectively controlling uneven subsidence of the subgrade. Sensitivity analysis shows that the factors influencing settlement, in descending order of impact, are pile length, pavement thickness, base layer modulus, and geogrid spacing. The length of the CFG piles is the key factor controlling settlement. When the pile length increases from 8 m to 15 m, the pavement settlement decreases from 9.8 cm to 1.4 cm, a reduction of 85.7%. The combined solution of geogrid + CFG piles has the lowest life-cycle cost.