【作者】 何永强；

【导师】 朱彦鹏；

【作者基本信息】 兰州理工大学 ， 结构工程， 2010， 博士

【摘要】 随着国家经济的不断发展,我国西北黄土地区建设中遇到的大厚度湿陷性黄上地基处理问题越来越多,消除湿陷性黄土地基的湿陷性,降低压缩变形,提高承载力成为当前工程界探求解决的一项技术难题。本论文结合挤密桩复合地基在湿陷性黄土地区地基处理中的应用现状,对素土挤密桩复合地基、灰土挤密桩复合地基及生石灰挤密桩复合地基在大厚度湿陷性黄土地基处理中的理论和应用进行了深入研究,并取得了一定的成果。本论文的主要工作包括：首先,基于圆孔扩张理论,采用弹塑性理论分析了三种挤密桩复合地基成桩过程中桩间土体的应力变化规律,并把土体看作Mohr-Coulomb材料,得到了挤密桩圆孔扩张理论的统一解。其次,根据挤密桩复合地基的特点,详细研究了横向挤密条件下桩间土的物理力学参数变化规律,并建立了相应的桩间土物理力学参数变化规律的量化计算公式；同时,基于孔隙挤密原理,推导出了生石灰挤密桩加固地基时所需生石灰桩数和生石灰体积的计算公式。第三,通过对挤密桩复合地基承载力计算方法的研究,综合分析了各影响因素对生石灰挤密桩复合地基承载力的影响,并分别推导出了生石灰桩膨胀量的理论值、桩体侧向膨胀引起的单桩总侧阻力增量、膨胀率对桩土界面法向正应力的影响、膨胀率对单桩竖向承载力的影响及生石灰桩膨胀对桩间土承载力影响的量化公式。最后,利用数值模拟(FLAC 3D)和实际工程的现场、室内土工试验,综合评价了采用素土挤密桩、灰土挤密桩、生石灰挤密桩复合地基时桩间土的挤密效果及复合地基承载力。试验结果表明生石灰挤密桩复合地基承载力远大于现行规范值,可见在实际工程中,规范值偏于保守,建议在有试验条件的情况下适当提高生石灰挤密桩复合地基的承载力设计值。生石灰挤密桩复合地基探井开挖试验表明,在大厚度湿陷性黄土地区,由于地基土的含水率较低,在采用生石灰挤密桩进行地基处理时,现行28d休止期内生石灰不能达到充分熟化,对桩间土的挤密效果不能完全发挥,建议适当延长休止期,这将对工程建设有利。综上所述,本文工作较全面地研究了挤密桩复合地基的加固机理,并为挤密桩在大厚度湿陷性黄土地基处理的设计计算提供了可靠的理论和技术支撑,从而丰富和完善了挤密桩复合地基理论和技术更多还原

【Abstract】 With the development of economy, more and more foundation treatment problems of collapse loess with large thickness in construction field should be solved on loess of northwest China. To eliminate the collapsibility, decrease the Compression Deformation and enhance the bearing strength of collapse loess has become a difficult technical problem that need to be solved by engineers. In this thesis, by associated with the practical situation of applications in compaction pile composite foundation in loess, the theories and applications of loess compaction pile, lime-loess compaction pile and quicklime compaction pile composite foundation were lucubrated, and some suggestions were given to serve reference for further projects. The main content of this thesis includes:Firstly, based on the cavity expansion method, the stress variety discipline of soil between compaction piles during three different types piling process were studied according to elasto-plasticity theory. Moreover, when the soil was considered as the ideal Mohr-Coulomb material, its unified solutions were obtained.Secondly, based on the characteristics of compaction pile composite foundation, the variety discipline of physical and mechanical parameters of soil between piles were researched under the condition of horizontal pack-press, and its calculating formula of physical and mechanical parameters and compression modulus are presented. On the other hand, based on the principle of pore extruding, the computational formula for calculating the amount of expanding material of quicklime pile was deduced.Thirdly, by studying the calculate method of compaction pile composite foundation, the effect of influence factors of its bearing capacity was analyzed. Furthermore, the theoretical value of quicklime pile’s swell, the total pile side resistance increment which caused by quicklime lateral swelling, the influence of normal stress and vertical bearing capacity of quicklime expansion ratio at interface of pile-soil, and the quantitative management formula of soil between quicklime piles were deduced.Lastly, by utilizing laboratory and in-situ test of practical project and numerical simulation (FLAC 3D), the compaction effects of soil between piles and bearing capacity of composite foundation are synthetic evaluated. The test results of quicklime compaction pile show that the bearing capacity is great larger than guild regulations suggested value. So, it is suggest that the design ultimate bearing capacity can be improved in engineering practice. By the test result of dig well, it shows that the quicklime hasn’t cured completely in 28 days, it is because that the water content is low in loess. So we proposed that the time limit of repose need to be extend for more than 28 days.In summary, the work of this thesis present a comprehensive study of the compaction pile composite foundation strengthening mechanism, and provide a new theoretical and technical support to compaction pile composite foundation in thick loess ground treatment design and calculation. This will enrich and improve the compaction pile composite foundation theory and technology.更多还原