冲填软土地基深层加固的优化方案分析

OPTIMIZATION PLAN OF REINFORCEMENT ON DEEP DREDGER FILL OF SOFT GROUND

冲填软土地基需要经过地基处理后才能投入工程使用,处理方案一般为浅层地基处理如真空预压处理,但对于大面积大荷载堆载场地,浅层地基处理不足以保证地基稳定性,需进一步做深层地基加固。本文针对广州某造船基地大面积堆载场地,对经真空预压处理后的该类深厚冲填软土地基提出了搅拌桩地基、微型桩地基以及搅拌桩微型桩交错布设地基加固方案,并基于Biot固结理论和有效应力原理,采用有限元分析软件PLAXIS进行数值模拟,对土体选取基于修正剑桥模型的软土模型和Mohr-Coulomb模型,对搅拌桩和微型桩依次选取线弹性模型和弹性模型,计算得到不同加固方案的基础沉降量。基于不同桩型加固机理对计算结果进行进一步分析得出,对此类深厚冲填软土地基,相同桩长的搅拌桩地基加固效果较微型桩效果更明显;另通过对不同桩长搅拌桩地基加固效果的模拟计算,发现桩长为10m到15m的搅拌桩均能有效加固地基,但随着桩长的增加,加固效果未能显著提高。本研究为冲填软土地基深层加固的设计提供了一定的依据。

Dredger fill of soft ground can't be put into engineering until foundation treatment is finished.Shallow foundation treatment such as vacuum preloading is generally utilized to improve the strength of foundation.But for a large area loading ground,shallow foundation treatment is not sufficient to ensure the stability of the foundation. Therefore,a deep foundation reinforcement is needed.Three plans of deep foundation reinforcement are the mixing pile foundation,micro-pile foundation and the mixture of the two piles.They are proposed after vacuum preloading treatment for the dredger fill of soft ground of the shipbuilding base in this paper.Besides,the finite element method software PLAXIS is utilized to simulate the proposed plans in the framework of the Biot's consolidation theory and the effective stress theory.Soft Soil Model based on the modified Cam-clay Model is selected for muck and mucky soil.Mohr-Coulomb Model is selected for sand,clay and silty clay.Linear elastic model and elastic model are respectively for mixing piles and micro piles.Settlements of different plans are obtained by the calculation.Further analysis on the different types of foundation reinforcement is made with different mechanism. For this deep dredger fill of soft ground,the mixing pile foundation is better than the micro-pile foundation with the same length in improving the ground strength.Additionally,settlements of mixing pile foundation with different lengths are calculated.The mixing pile foundation with the length from 1 0m to 1 5m can improve the ground strength.However,the effect is not improved obviously as the length increases.The results can provide some basis for the design of a deep dredger fill of soft ground reinforcement.