Study on Optimization of Design Parameters for Precast Pipe Pile Treatment of Soft Soil Subgrade on the Jianghan Plain

Abstract

The soft soil in the Jianghan Plain is characterized by a high water content, liquid limit, sensitivity, porosity ratio, and organic matter content and low strength and is commonly known as “five highs and one low” soft soil. Thus, the construction of expressways in this area is likely to cause subgrade settlement. The manuscript investigated the influence of the design parameters of precast pipe piles on the soft ground treatment in the Jianghan Plain based on the case of the soft soil subgrade project of the Xiaogan south section of the Wuhan city ring expressway, China. Midas GTS NX 2019 finite element software was used to analyse the settlement pattern of the subgrade under the variations in pile length, pile spacing and pile diameter. The results show that precast pipe piles are effective in reducing the settlement of soft soil subgrades with a high compressibility and water content; the soft foundation settlement decreases with increasing pile length and pile diameter and decreasing pile spacing. As the pile tip is embedded in the bearing stratum, the settlement of the soft foundation is greatly affected by the variations in pile length and pile spacing while slightly influenced by the variation in pile diameter; in combination with the curve fitting obtained from the real-time monitoring data, the analysis concludes that the soft foundation treatment plan with a pile length of 15 m, pile spacing of 1.2 m to 1.5 m and pile diameter of 0.6 m can better contain the soft soil subgrade settlement in this section.