Application and Analysis of Bagged Sand Well in Soft Soil Foundation Treatment of Highway

Based on a highway project in Foshan, Guangdong Province, the in-situ monitoring data with bagged sand well surcharge precompression method were aquired from heap load to dead load, and the variation of surface settlement, stratified settlement, deep lateral displacement and pore water pressure in the soft foundation section were analyzed. The treatment effect of this method combined with the calculated post-construction settlement was also evaluated. The results show that the maximum settlement of the surface is 291 mm when the soft foundation loaded by 210 days, and the maximum settlement rate of the surface is 8.67 mm/d, which is less than the 10 mm/d limited by the standard. The stratified settlement of soft soil mainly occurs in the soil layer with a depth of 2～6 m, and the lateral horizontal displacement of the soft soil mainly occurs in the soil layer with a depth of more than 6 m, accounting for about 95% of the total displacement. In the whole process of filling preloading, the maximum comprehensive pore pressure coefficient B is 0.371, which is smaller than the 0.4 limited by the standard. The final settlement and post-construction settlement of soft soil subgrade are calculated by hyperbolic method. The post-construction settlement is controlled between 34～64 mm, which is less than the 200 mm limited by the standard. The research results can provide the basis for the design and construction of highway soft soil foundation in this area.