海相淤泥质土地基加筋滤网碎石桩竖向承载性能试验研究

为研究加筋滤网碎石桩竖向承载性能,对现场海相淤泥质软土地基,采用预成孔加筋滤网碎石桩处理。通过超重型动力触探、平板载荷试验对处理效果进行评价,分析加筋滤网碎石桩单桩竖向承载性能。通过建立加筋滤网碎石桩单桩有限元模型,分析加筋滤网包裹长度对碎石桩单桩承载性能的影响规律。结果表明:加筋滤网碎石桩单桩竖向承载力特征值约是普通碎石桩的2.4倍;加筋滤网对碎石桩的侧向约束作用、承载力贡献均存在尺寸效应,对HP470型加筋滤网,当桩体直径大于1 200 mm时,加筋滤网对桩身的侧向约束作用减弱,对承载力的提高作用减小,碎石桩体发挥主要作用;加筋滤网碎石桩(2～3)d(d为桩径)深度范围内桩体碎石密实度对单桩竖向承载力有显著影响,对由桩顶至3d深度范围内的碎石经3 000 kN·m能级强夯加固,单桩竖向承载力特征值较夯前提高约4.1倍;当竖向荷载P=200～250 kPa时,对于HP470型加筋滤网,在满足承载力和变形的要求下,可选择包裹长度6d为最小包裹长度。研究成果可为加筋滤网碎石桩优化设计提供依据。

Experimental Study on Vertical Bearing Capacity of Single Geotextile-encased Granular Column in Marine Silty Clay

Pre-drilled geotextile-encased granular columns were installed in silty clay. The reinforcement effect was evaluated through ultra-heavy dynamic penetration tests and plate loading tests, and the vertical bearing capacity of single geotextile-encased granular column was examined. The influence of geotextile-encased length on the vertical bearing capacity of single geotextile-encased granular column was investigated by building a finite element model of single column. Results unveiled that the characteristic value of vertical bearing capacity of single geotextile-encased granular column is about 2.4 times that of single ordinary granular column. Scale effect was found in the lateral constraint and contribution of bearing capacity to the column: the improvement to lateral constraint and bearing capacity weakens and the granular stone works as main component when the diameter of column is 1 200 mm with geotextile type of HP470. The compactness of granular stone exerts a remarkable influence on vertical bearing capacity in the depth ranging from (2-3)d (d represents diameter of column). Through dynamic compaction (3 000 kN·m) on granular stones in the depth range from column top to 3d, the vertical bearing capacity of the column increased by about 4.1 times. Under the requisite of guaranteeing bearing capacity and deformation, we suggest 6d as the minimum encased length (geotextile type of HP470) when vertical load is 200-250 kPa.