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深厚软弱土层中水泥土加固被动区的基坑稳定分析

更新时间 2009-9-5 12:12:46 点击数:

毕业论文标题】 深厚软弱土层中水泥土加固被动区的基坑稳定分析
【英文标题】 Stability Analysis of Deep Soft Soil Excavation of Cement-soil Reinforcement in Passive Zone
【中文摘要】 在深厚软土地区的基坑工程,由于软土土质条件较差且土层较厚,会出现坑内被动区土压力不足,坑底对支护桩的约束作用较弱的现象。在基坑支护设计中需要通过增加桩长来增强土体对支护桩的约束,但是这样不但增加了工程造价且约束效果不太明显。在基坑被动区进行水泥土加固,可以提高被动区抗力,提高基坑稳定性,为支护桩提供很好的嵌固层,是一种较为经济有效的技术措施。由于加固土强度具有时效性,目前还没有配套的理论同时考虑水泥土、软土、支护桩三者的共同作用。围绕这一问题,本文针对南沙地区的软土,对其掺加水泥加固,研究水泥土强度的时效性,并将试验成果运用到计算之中,具体内容如下:1.以实际工程为背景,研究分析水泥土微观结构,探讨其加固机理;同时对不同水泥掺量、水灰比、外加剂的水泥土土分别进行龄期为7d、14d、28d、90d龄期的无侧限强度试验,获得相应的水泥土基本特性及其强度随时间变化的规律。2.归纳总结深厚软土地区的基坑支护方式。结合具体基坑工程,对被动区进行加固设计及基坑稳定性分析,通过在计算中采取不同的被动区强度参数而将水泥土强度随时间变化的特性考虑在内。3.对深厚软土层被动区加固的基坑开挖与支护过程进行数值模拟和有限元分析。在建模的过程中水泥土和软土采用Drucker-Prage材料模型,支护桩和支撑采用梁单元。将试验成果运用到计算中,考虑施工时间间隔而采用不同龄期的水泥土强度。获得考虑水泥土、软弱土、支护结构共同作用的基坑变形特征和稳定特征;分析水泥土强度变化在各步施工工序中对基坑稳定及变形的影响,为此类深厚软土层下的中小型基坑支护及施工工序提供理论依据和实用参考

【英文摘要】 In the soft soil excavation,due to the properties and thick soil layer,soil pressure in the passive zone is not enough,this leads to the restriction from the base to pile becoming weak.In the design of excavation supporting system,the improvement of restriction is achieved by increasing the pile length.But this will result in higher budget and the effect is not very obvious.Reinforcement in passive zone by using cement-soil will generate soil pressure,enhance excavation capacity and provide build-in force for piles.Overall,reinforcement in passive zone is an economical and effective technical method.Due to the time effect on properties of reinforced soil,until now,no theory is raised which considers cement-soil,soft soil and supporting pile at the same time. Based on this topic,this paper focuses on the research of cement-soil reinforcement, time-effects on its strength in Nansha area.And apply experiment result into calculations,which is described as follows.Take a practical project for case study,analyze the micro structure of cement-soil,research on its reinforcement mechanism;in the meanwhile,conduct unconfined strength test respectively under 7d,14d,28d,90d,as per different cement content,water cement ratio,additive.Obtain relevant properties of cement-soil as well as the fact that strength changes in terms of time.Conclusion is derived on the methods for the excavation supporting system in deep soft soil zone.Reinforcement design for passive zone and analysis of excavation stability are presented via specific project case study.The analysis is undertaken in consideration of the fact that the cement-soil strength is changing towards time,this is achieved by adopting different strength factors in passive zone.Numerical modeling and finite element analysis are performed for the reinforced deep soft soil excavation and excavation supporting system in the passive zone. Drucker-Prage material model is adopted for the cement-soil and soft soil in the modeling process;pile and excavation support is modeled as beam element.Result which is derived from experiment is applied,and consider construction time interval, different cement-soil strength regarding to different concrete age are used.The characteristic of excavation deformation and stability is monitored,which is under the consideration of cement-soil,soft soil and supporting element.Moreover,accurate analysis is undertaken,which is on the effects of cement-soil strength change towards excavation stability and deformation in terms of construction steps.Therefore, theoretical basis and practical reference are provided to such medium-small excavation supporting system and construction procedures in deep soft soil.

【中文关键词】 深厚软土基坑; 水泥土被动区加固; Drucker-Prager模型; 室内试验; 数值方法
【英文关键词】 deep soft soil excavation ; cement-soil reinforcement in passive zone; Drucker-Prager model ; indoor experiment ; numerical method
【论文目录】
摘要 4-5
Abstract 5-6
第1章 绪论 8-24
    1.1 引言 8
    1.2 软土的特性 8-11
    1.3 深厚软弱土层中基坑工程研究现状 11-13
    1.4 被动区加固的研究现状 13-23
    1.5 本文研究目的及主要研究内容 23-24
第2章 深厚软土基坑被动区加固设计 24-35
    2.1 深厚软土层的基坑支护方法 24-28
    2.2 坑内被动区土体土质加固设计算例 28-35
第3章 被动区加固的水泥土室内试验 35-53
    3.1 水泥土的加固机理及微观试验 35-41
    3.2 水泥土的力学特性 41-44
    3.3 水泥土室内试验 44-53
第4章 考虑被动区加固的软弱基坑稳定有限元模型 53-76
    4.1 有限元单元法 53-55
    4.2 材料模型的选择 55-61
    4.3 有限元模型的建立及网格的划分 61-64
    4.4 计算成果及分析 64-76
第5章 结论与展望 76-78
    5.1 结论 76-77
    5.2 有待于进一步研究的问题 77-78
参考文献 78-82
致谢 82

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