基于联合求解法的疏桩地基沉降计算方法研究

疏桩基础作为一种工期短、效果好的软土地基处理方式，在工程中的应用越来越广泛。考虑带桩帽的PTC（预应力混凝薄壁管桩）刚性桩桩侧摩阻力分布规律，将桩侧摩阻力假定为2个三角形拼合的分布形式。联合应用Mindlin-Geddes解答及Boussinesq解答，推导出了疏桩补偿地基中的附加应力的计算公式。结合具体算例，计算复合地基的沉降变形量。研究表明，该联合方法的沉降计算结果比传统方法偏小，与实测数据较为吻合。当桩间距大于8倍桩径时，随着桩间距的增加，疏桩补偿地基的附加应力场基本不变，但沉降量相应增大。对于桩间距较大的疏桩补偿地基，采用长、短桩组合形式较为合理。通过设置深层水泥土搅拌桩来加固软土路堤，能有效控制沉降量。

Calculation of ground settlement of sparse pile foundations using united solutions

The composite foundation with sparse piles is widely used in practice as a time-saving and effective way to treat soft soil.Considering the distribution law of skin frictions on capped PTC(prestressed thin-wall concrete pile) rigid piles,this study assumes that the distribution of skin frictions can be simplified as two triangles.Combining Mindlin-Geddes’ solution with Boussinesq’s solution,the formula of additional stresses of the sparse pile foundation can be derived under the full consideration of the radius of influence.In numerical cases,the ground settlement can be determined using the layerwise summation method.The authors compared the results from the traditional calculation method and the united solutions and analyzed the variation of calculated ground settlement using united solutions while the pile spacing varies.The proposed combined method is used to analyze the settlement of the sparse pile foundation for ground treatment.The results show that the calculated settlement is smaller than that from the traditional method and fits well with the monitoring results.When the pile spacing is eight times larger than pile diameter,as the pile spacing increases,the additional stress field shows no significant variation but the settlement increases accordingly.For foundations with a large pile spacing,the utilization of the long-short-pile composite foundation is preferable.With the installation of deep cement mixing piles,the soft embankment can be reinforced and the ground settlement can be effectively reduced.