【作者】 李其泽；

【导师】 陈昌富；

【作者基本信息】 湖南大学 ， 岩土工程， 2011， 硕士

【摘要】 碎石桩复合地基以其良好的工程性能被广泛应用于路堤、桥梁、蓄水池、港口以及低矮民用建筑的加固处理中。当采用碎石桩加固软土时,其承载性能的发挥主要取决于桩侧土体水平方向约束力的大小。为了提高侧向约束力,实际工程在桩顶设置土工合成材料或钢筋混凝土套筒,通过采用这一新型技术,碎石桩承载性能得到了极大改善。针对加箍碎石桩承载力研究不足的现状,本文以圆孔扩张理论为基础,主要进行了以下工作:⑴探讨了荷载作用下加箍碎石桩的承载机理及其破坏模式。在传统圆孔扩张理论的基础上,采用Mohr- Coulomb屈服准则,考虑土体自重效应和加箍段桩侧摩阻力的影响,推导出加箍碎石桩单桩极限承载力的计算公式。⑵以弹性力学平面问题基本方程和塑性理论为基础,考虑扩张重叠作用的影响,建立了新的加箍碎石桩群桩计算模型,推导出考虑群桩相互作用的承载力计算公式。通过对相关参数进行分析,探讨了本文方法与传统扩张理论在加箍碎石桩承载力计算上的差异。⑶基于统一强度理论,提出了加箍碎石桩径向应力计算式,推导出加箍碎石桩单桩和群桩承载力计算公式,并进一步研究了强度计算准则对加箍碎石桩承载力计算结果的影响。⑷结合工程实例,比较分析现场载荷实验与本文方法的计算结果,验证了本文群桩模型承载力计算公式的可行性。通过分析研究单桩模型与群桩模型在计算结果上的差异,探讨了群桩作用在加箍碎石桩承载力计算中的必要性。更多还原

【Abstract】 Owing to its good engineering performances, stone columns composite foundation has been widely used in the reinforcement processing of road embankment, bridges, ports and civil buildings. When stone column be used in soft soil,the perofrmances of it’s bearing capacity usually limited by lateral confinemet from the soil. And setting geosynthetics at the top of stone column or using reinforced concrete sleeves are being applied in projects, through which technology bearing capacity of stone column is greatly improved. In this paper,the cavity expansion theoren was considering,and on the basis of which it also completes other main work as follows:⑴In order to analyse the geosynthetic-encased stone column,based on the column cavity expansion theorem and considering the influence of the soil gravidity stress,the ultimate bearing capacity calculation formula of single pile was deduced when Mohr-Coulomb yield criterion was adpoted.⑵The bearing capacity calculation method of geosynthetic-encased gravel piles was established in the premise of considering expansion overlap.And the bearing capacity calculation formula of pile groups also given in this paper.It was further pointed out that this method was very different from the traditional cavity expansion theory.⑶On the basis of the unified strength theory, the bearing capacity formula for both single pile and pile groups was proposed.Under the further study of effects by different strength criteria,the infulence to the ultimate bearing capacity was also analyzed in this paper.⑷In order to validate the proposed method,a case history was illustrated. the result demonstrates that the calculation models of single pile and pile groups was practicability. And the further analyses indicates that in the calculation of bearing capacity of geosynthetic-encased stone columns considering the effects between pile groups were very necessary.更多还原