路堤下钉形搅拌桩复合地基沉降计算方法——广义桩体法

针对钉形搅拌桩这种变截面搅拌桩,通过一定的假设,将其简化为上、下直径相等而模量不等的常规等截面桩,提出了钉形搅拌桩复合地基沉降计算方法--广义桩体法。根据位移、应力连续条件,将路堤填土、加固区和下卧层作为统一的整体,提出了考虑桩顶上刺、桩土相互作用和桩端下刺的加固区计算模型,并建立了模型的有限差分解法。基于三维数值模拟结果,提出考虑路堤下钉形搅拌桩复合地基下卧层应力集中的附加应力计算方法,从而建立路堤荷载下钉形搅拌桩复合地基的沉降计算方法。计算实例表明:复合模量法计算结果偏小,而应力修正法偏大,本文方法最接近实测结果,说明其具有一定的适用性。

Generalized column method for calculation of settlement of T-shaped deep mixed column composite foundation under embankment load

T-shaped deep mixed column is a new type of soil-cement deep mixed column with varied cross-section areas. In this study, the T-shaped column is simplified as the conventional shaped column with varied deformation modulus with some assumptions. The settlement calculation method of T-shaped deep mixed column composite foundation called generalized column method is presented. Based on the displacement and stress continuity, the embankment, improved area and substratum are treated as a whole. The settlement calculation models for composite foundation under embankment load are developed considering the penetration of column tops, interaction between columns and surrounding soil, and penetration of column ends. A finite difference method is used to carry out the calculation. Based on the 3D numerical simulation results, a simplified method is proposed to calculate the additional stress in substratum under embankment load. The proposed methods are employed to calculate the settlement in field sites, and the results are compared with the measured data as well as the results calculated by other methods. The comparisons indicate that the settlement calculated using the composite modulus method is smaller than the observed data, while the calculated data using the modified stress method is too larger than the observed data. However, with the proposed method, the calculated data is well consistent with the measured data.