高填方路堤段桩网复合地基承载机理及桩土应力比计算方法

针对高填方段软土路基在路堤荷载下桩网复合地基的受力特点,分析了其自上而下的荷载传递机理.首先,将路堤简化为内外土柱,通过内外土柱的整体微分平衡关系,得到了等沉面高度的理论计算式,由此较为合理地模拟了高填方段的土拱效应.而后,针对荷载传递至土工垫层阶段,采用薄膜模拟了桩土之间的荷载分配关系.在此基础上,将桩网复合地基划分为众多土工格栅、桩及桩间土单元体,桩体及桩间土简化为弹性支撑,进一步得到了高填方段桩网复合地基桩土应力比计算式.最后,对影响高填方段桩网复合地基桩土应力比的各主要影响参数进行了初步研究.结果表明,桩土应力比随路堤高度增大逐渐减小,即填土高度增加后桩土荷载分配趋于均匀,而桩间距、填土的压缩模量的增大将导致桩土应力比增加.此外,土工格栅抗拉强度的增大将加大桩土应力比值,但影响幅度较小.

Pile-net Composite Foundation Bearing Mechanism and the Method to Calculate the Pile-soil Stress Ratio in High Embankment

According to the mechanical characteristics of pile-net composite foundation of high fill section of soft soil subgrade under embankment load, this paper made an in-depth analysis of the load transfer mechanism from the top to the bottom. Firstly, embankment soil was simplified as an inside and outside column. Then, according to integral differential balance between the inside and the outside soil column, the height of the initial plane of equal settlement can be derived and the soil arch effect of high embankment fill can be reasonably simulated. Secondly, when the load transfers to the geotechnical cushion layer, thin film is used to simulate the load distribution between the pile and the soil. Based on the results of previous derivations, pile-net composite foundation can be divided into geogrid, pile and soil elements between the pile bodies. The pile and the soil between the piles were simplified as an elastic support. The pile-soil stress ratio calculation formula of the high fill section pile-net composite foundation can be derived. Finally, this paper studied the main influence parameters of the pile-net composite foundation pile-soil stress ratio in the high fill section. The results show that, with the increase of embankment height, the pile-soil stress ratio decreases, namely, with the increase of fill height pile and soil, the load distribution tends to be more uniform, but the increase of pile spacing or the compression modulus will increase the pile-soil stress ratio. Furthermore, the increase of geogrid tensile strength will cause the increase of pile-soil stress ratio, but the influence of geogrid tensile strength is small.