侧向约束下柔性桩复合地基沉降特性

Settlement Characteristics of Composite Foundation Reinforced by Flexible Piles with Lateral Restraint

侧向约束技术在地基处理工程中能有效地减小地基沉降。本文结合铁路工程与软土工程特性,采用模型试验与数值模拟的方法,研究了侧向约束(桩)对柔性桩(夯实水泥土桩)复合地基沉降的影响,分析了柔性桩和土体沉降变化随荷载水平的变化规律,探讨了侧向约束条件下土体模量、桩间距等因素对地基沉降的影响。研究结果表明:在柔性桩复合地基中设置侧向约束桩,当土体压缩模量较小时,采用2d(d为桩径)或3d桩距皆能较好地降低桩的沉降量;随着土体压缩模量的增大,桩距采用3d时减沉作用降低、2d时减沉效果增强、4d时减沉作用不明显;桩间土体沉降量在桩距为2d及3d时,减沉作用呈现先减小后增大的特点,4d时其沉降量减小比值为4%~5%。因此,合理设置侧向约束桩才能有效限制软土侧向挤出,以达到减少复合地基沉降的目的。

Lateral restraint technique can effectively reduce the ground settlement during the treatment practice of soft soil foundation. Based on the characteristics of road engineering and engineering properties of soft soil, the effect of lateral restraint （pile） on the settlement of composite foundation reinforced by flexible pile （rammed soil-cement pile） was studied by means of model experiment and numerical simulation. Furthermore, the changing patterns of pile and soil settlement with the loading level were analyzed, and the influence of soil modulus and pile spacing on foundation settlement was discussed taking the lateral restraint condition into consideration. The results revealed that when lateral restraint piles were applied to the composite foundation reinforced by flexible pile, the pile spacing of 2d （d is pile diameter） and Sd both reduced the pile settlement effectively if soil compression modulus was low; as the soil compression modulus increased, the settlement reducing effects decreased when pile spacing was 3d, and it increased when pile spacing was 2d, while the settlement reducing effects can hardly be observed when pile spacing was 4d. However, as the piles spacing was 2d and 3d, the reducing effect to soil settlement decreased first and then increased; when pile spacing of 4d was applied, the reduced amount of the settlement was around 4 %- 5%. Therefore, a reasonable setting of lateral restraint pile was required for effectively restricting the lateral extrusion of soft soil, and consequently reducing the settlement of composite foundation.