强夯置换碎石墩复合地基承载机理及稳定评价

发布时间：2018-03-22 15:56

本文选题：体积置换率　切入点：强夯置换碎石墩　出处：《东北大学》2014年硕士论文　论文类型：学位论文

【摘要】：强夯置换碎石墩复合地基同时具有强夯置换和排水固结加固软弱地基的优势,在加固填海地层方面有着巨大的优势。强夯置换法是在强夯法的基础上发展起来的,但又和强夯法有着显著的不同点,然而目前针对强夯置换的研究工作十分匮乏,参考文献极其稀少,机理还不明确。本文结合大连航天城实际工程,围绕强夯置换碎石墩复合地基的基本特性、承载机理开展了以下研究工作：在总结分析强夯碎石墩基本特性的基础上,发现强夯置换形成的碎石墩由于受到夯锤的影响,会产生明显的鼓出效应,用碎石墩表面积与周围加固土体的面积之比已经不能准确地反映出实际工程中复合地基的置换率,提出了体积置换率的概念,用墩体体积与被加固土体体积之比来表示,同时得出了体积置换率与面积置换率的换算关系,即在原有的面积置换率公式之上乘以一个增大系数α(α=1.25～1.6)来表示体积置换率。考虑到墩体的鼓出效应,提出了适当减小设计墩径,利用简化的鼓形和漏斗形模型确定了工程上可以使用的墩体改进值,并且用数值模拟手段证明了此方法的合理性。同时,利用有限差分软件FLAC3D,考虑垫层厚度、墩体形式、墩体直径、置换率等因素对复合地基极限承载力的影响,建立了不同工况下的复合地基三维数值模型,详细模拟和讨论了墩间土和墩体的极限承载力随着这些因素的变化规律,给出了这些因素的影响范围,为可以最大限度发挥极限承载力的复合地基方案提供了参考。系统讨论了强夯置换法中的各项参数,提出了强夯置换碎石墩复合地基的施工工艺、质量控制指标和要求,将上述强夯参数和数值分析得到的参数运用到实际工程中,检测施工后的地基承载力,验证参数的合理性；采用提出的体积置换率进行了地基承载力的计算,说明了此方法的合理性。
[Abstract]:The composite foundation of dynamic tamping replacement gravel pier has the advantages of dynamic tamping replacement and drainage consolidation to reinforce weak foundation, and has great advantages in strengthening the reclaimed ground. The dynamic tamping replacement method is developed on the basis of dynamic compaction method. However, there are significant differences between the dynamic compaction method and the dynamic compaction method. However, the research work on the dynamic tamping replacement is very scarce, the references are extremely rare and the mechanism is not clear. This paper combines the actual project of Dalian Aerospace City, According to the basic characteristics of dynamic tamping replacement macadam pier composite foundation, the following research work is carried out on the bearing mechanism: on the basis of summarizing and analyzing the basic characteristics of dynamic tamping crushed stone pier, it is found that the macadam pier formed by dynamic tamping replacement is affected by rammer. The ratio of surface area of gravel pier to the area of surrounding reinforced soil can no longer accurately reflect the replacement rate of composite foundation in actual engineering, and the concept of volume replacement rate is put forward. The ratio of the volume of the pier body to the volume of the reinforced soil is expressed, and the conversion relationship between the volume replacement rate and the area replacement rate is obtained. That is to say, the volume displacement rate is expressed by multiplying an increase coefficient 伪 (伪 ~ (1. 25) ~ (1.6)) over the original formula of area replacement rate. Considering the bulging effect of the pier body, a proper reduction of the diameter of the designed pier is put forward. Using the simplified drum and funnel models, the improved values of the piers can be used in engineering are determined, and the rationality of the method is proved by numerical simulation. At the same time, by using the finite difference software FLAC3D, the thickness of cushion and the form of pier are considered. The influence of piers diameter and replacement ratio on ultimate bearing capacity of composite foundation is studied. A three-dimensional numerical model of composite foundation under different working conditions is established, and the variation law of ultimate bearing capacity of soil and pier body between piers with these factors is simulated and discussed in detail. The influence range of these factors is given, which provides a reference for the scheme of composite foundation which can maximize the ultimate bearing capacity. The parameters of dynamic tamping replacement method are discussed systematically, and the construction technology of dynamic tamping replacement gravel pier composite foundation is put forward. The parameters of dynamic compaction and numerical analysis are applied to the actual engineering to test the bearing capacity of the foundation after construction and verify the rationality of the parameters. The calculation of the bearing capacity of the foundation is carried out by using the proposed volume replacement ratio, which shows the rationality of the method.
【学位授予单位】：东北大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU472.31

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