深厚自重湿陷性黄土场地灌注桩基础设计

Design of cast-in-place pile foundation in deep self-weight collapsible loess site

对于深厚自重湿陷性场地的桩基础设计,通过桩端后注浆工艺减少桩基沉降、提高桩端持力层的端阻力,通过桩基静载试验确定注浆后桩端持力层的实际承载力,采用强夯处理或回填压实消除深厚自重湿陷性黄土场地上部一定深度范围内湿陷性土层的湿陷性,同时提高上部土层的密实性以提高桩侧摩阻力以及加强上部土层防水效果以达到减少桩侧负摩阻力的目的,结合三七灰土防水垫层的防水作用,将湿陷性土层有害的桩侧负摩阻力变为对桩基竖向承载力有利的桩侧正摩阻力,可以大幅度提高桩基的竖向承载力,使位于深厚自重湿陷性场地的桩基础设计做到技术可行且经济合理。

For the design of pile foundation in deep self-weight collapsible site,the settlement of pile foundation was reduced and the end resistance of pile end bearing layer was increased by post-grouting technology at pile end.The actual bearing capacity of pile end bearing layer after grouting was determined by static load test of pile foundation.The collapsibility of collapsible soil layer in a certain depth in the upper part of deep self-weight collapsible loess site was eliminated by dynamic compaction treatment or backfilling compaction.At the same time,the compactness of the upper soil layer was improved to improve the pile side friction resistance and enhance the waterproofing effect of the upper soil layer in order to reduce the pile side negative friction resistance.Combined with the waterproofing effect of lime-soil waterproof cushion,the negative skin friction resistance of collapsible soil layer was changed into the positive skin friction resistance of pile side,which was beneficial to the vertical bearing capacity of pile foundation.The vertical bearing capacity of pile foundation could be greatly improved,and the design of pile foundation in deep self-weight collapsible site could be technically feasible and economically reasonable.