径竖向渗流下竖井-碎石桩复合地基固结解

CONSOLIDATION SOLUTION FOR COMPOSITE FOUNDATION WITH VERTICAL DRAINS-STONE COLUMNS CONSIDERING RADIAL AND VERTICAL FLOW IN SOFT SOILS

  • 摘要: 在碎石桩间增设排水板可提供更多的竖向排水通道以加速软土地基固结,同时桩周土体的快速固结使碎石桩复合地基早期承载力显著提高。但目前同时考虑两种竖向排水体的复合地基固结理论还鲜见报道,致使其早期承载力和沉降变形计算缺乏理论依据。基于此,以竖井-碎石桩复合地基为研究对象,考虑土体中的竖向渗流及其在两种竖向排水体间的径向渗流,在复合地基顶面排水、底面不透水的条件下,根据桩体、竖井和桩周土体渗流流量相等的连续条件,建立考虑土中水径竖向渗流的竖井-碎石桩组合型复合地基固结模型并获得模型的解析解。该解析解可分别退化为考虑径竖向组合渗流的碎石桩复合地基固结解析解和经典竖井地基固结解析解。最后利用该解析解开展大量的分析计算以了解组合型复合地基的固结性状。结果表明:桩间增设竖井后可明显提高复合地基的固结速率;碎石桩桩体的涂抹效应对固结速率有明显影响,而竖井的涂抹效应对固结速率的影响甚微。在设置竖井的条件下,可仅考虑桩间土径向渗流对土体固结的加速作用。

     

    Abstract: Installing vertical drains between stone columns can provide more vertical drainage paths to accelerate the consolidation of soft soils. The faster consolidation of soils around columns provides the larger bearing capacity of a composite foundation. However, consolidation theories of the composite foundation considering two vertical drainage bodies have been rarely reported in the literature. As a result, its bearing capacity and settlement calculation is out of theories. On the basis of the study status, the composite foundation with vertical drains-stone columns was regarded as an object. The radial seepage of pore water in the soil around columns to two vertical drainage bodies and the vertical upward seepage were considered. Under the condition that the top surface of composite foundation is permeable and the bottom surface is impermeable, a consolidation model for the composite foundation with vertical drains-stone columns were developed according to the continuity condition of the flow volume among vertical drains, stone columns and soils, and an analytical solution for the consolidation model was derived. This analytical solution can be reduced to the analytical solution for the consolidation of composite foundations with stone columns by considering radial and vertical seepage and the consolidation of soils with classical vertical drains, respectively. Finally, the analytical solution is used to carry out a lot of analysis and calculation to investigate consolidation behaviors of this composite foundation. The results show that the consolidation rate of composite foundation greatly increases by installing vertical drains among stone columns. The smear effect of stone columns has great influences on the consolidation rate, but the smear effect of vertical drains has little influence on the consolidation rate. If vertical drains are installed among stone columns, only the radial seepage in soils around columns can be considered to accelerate the consolidation rate of soils.

     

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