深层搅拌桩论文：黄河三角洲咸水区水泥土深层搅拌桩复合地基承载与沉降特性研究.doc

深层搅拌桩论文：黄河三角洲咸水区水泥土深层搅拌桩复合地基承载与沉降特性研究【中文摘要】黄河三角洲是年轻陆地,广泛分布着以低液限粉土、含砂的亚粘土、粉砂土为主的沉积土,工程性质差,有些地区甚至是欠固结土,为减小高填方路基等上部建筑物过大的不均匀沉降,往往采用水泥土深层搅拌桩对地基进行加固,但黄河三角洲地区存在大面积地下咸水,地下水和土的矿化度都很高。前期研究已表明,咸水拌和水泥土的耐久性很差,由此会引起搅拌桩复合地基承载性能发生衰变,最终导致路基等上部建筑发生过大沉降(如桥头跳车现象)或失稳破坏,这将导致复合地基实际短寿命与道路等上部结构设计长寿命不协调的现象,不仅带来国有资产的浪费,而且产生很坏的社会影响。本文在对黄河三角洲典型区域地下水质和土力学性质进行调查和分析基础上,利用试验和理论等综合手段,对水泥土力学性能的衰变特性及其对复合地基整体承载性的影响等进行了系统研究：1、以滨德高速公路k15+155.5-k15+205.5段作为试验段,对黄河三角洲咸水区土和水的特性进行了调查与分析；2、基于室内试验,研究了黄河三角洲咸水区水泥土力学特性随时间的变化规律,并与正常水泥土进行了比较分析；3、为了研究黄河三角洲咸水区水泥土桩复合地基的沉降和承载特性,进行了1：50的模型试验研究。研究发现水泥土劣化将使复合地基沉降明显增大,复合地基承载性能降低；桩体缺陷将加快严酷地下咸水环境下的水泥土劣化,进而导致搅拌桩复合地基的沉降明显增大,所以在黄河三角洲搅拌桩施工中更应该严格控制施工质量；适当减小边桩长度,工程成本明显减小,但复合地基总体承载性能变化不大,在设计中值得推荐。本文为黄河三角洲咸水区复合地基的耐久性设计提供了理论支撑和技术指导,具有重要的经济和社会意义。本文受到国家自然科学基金项目(51078222；50708056)和山东大学自主创新基金杰出青年培养项目(2010JQ001)的资助。【英文摘要】The Yellow River Delta is a new-formed land, with the wide distribution of the sedimentary soil mainly composed of low liquid limit powder soil, sand-contained sub-clay and silty soil, all of which above show poor engineering properties and even parts have developed the underconsolidated soils. To reduce the excessive uneven settlement brought by the upper buildings, for instance the high-fill subgrade, soil-cement deep mixing pile of foundation reinforcement is frequently adopted. However in the Yellow River Delta areas, there exists a large scale of salty water, groundwater and subsurface soil with high level of salinity. Previous research has shown that the durability of cement-soil mixed with salt-water is poor, which may cause the bearing capacity of mixing pile composite foundation decay, and eventually lead to the excessive settlement of upper buildings such as roadbed (this settlement probably induce the phenomenon of bridge head bump) or instability and failure of composite foundation. Those distresses will result in the uncoordinated phenomenon between the short life of the composite foundation and the long life of upper structure design, bringing in state-owned assets waste.This paper,based on the survey data on the quality of groundwater and the mechanical properities of soils spreading around the Yellow River Delta regions systematically study the decay of cement-soil characteristics and its mechanical properties of composite foundation,exploring a comprehensive methods including test, theory numerical analysis and etc.1. This research chooses Binzhou-Dezhou Highway K15+155.5K15+205.5 as the testing area to analyse the characteristics of soil and water of salt-water area in the Yellow River Delta.2. Based on the laboratory test, this paper studies the regulations over time on the soil-cement mechanics properties of salt water area in the Yellow River Delta, compared with the normal soil-cement, meanwhile.3. The model simulation test with the ratio of 1:50 was conducted to study the settlement and bearing capacity of cement pile composite foundation in the salt-water area of the Yellow River delta. And it was found that the cemen-soil degradation caused settlement increase obviously and bearing capacity of the composite foundation decay, then the design scheme taking the durability of cement-soil into account. In the meanwhile, pile defection will speed up cement-soil degradation in the salt-water area, leading to the settlement of the mixing composite foundation increases obviously, so its necessary to pay more attention to controlling construction quality in the Yellow River delta; At last, its wise to decrease the length of pile in the edge, for it can save the construction cost without affecting the composite foundation bearing capacity.Based on above fundementaly research, this study provided theoretical support and technical guidance on the the durability design of composite foundation. And it will gain vast economic benefit and social meaning.This work was supported by the Chinese Natural Science Foundations (Nos.51078222,50708056 and 50978207) and Independent Innovation Foundation of Shandong University, IIFSDU (No.2010JQ001).【关键词】深层搅拌桩 黄河三角洲 咸水区 腐蚀 模型试验【英文关键词】Deep mixed pile Yellow River Delta salt-water area corrosion model test【目录】黄河三角洲咸水区水泥土深层搅拌桩复合地基承载与沉降特性研究摘要8-9ABSTRACT9-10第一章 绪论11-211.1 研究背景与意义11-121.2 国内外研究进展与分析12-171.3 研究内容17-181.4 创新点181.5 技术路线18-21第二章 黄河三角洲地下咸水区土水特性调查与分析21-272.1 黄河三角洲地下水的演化21-222.1.1 古黄河三角洲21-222.1.2 近代和现代黄河三角洲222.2 试验段土的化学特征分析22-252.2.1 取土样位置22-232.2.2 土样的易溶盐含量试验23-242.2.3 土样的定名及含盐量分析24-252.3 地下咸水理化分析25-262.4 小结26-27第三章 黄河三角洲含盐水泥土力学特性时变规律试验研究27-453.1 水泥土固化原理27-293.2 水泥土室内试验29-453.2.1 试验目的29-303.2.2 试验内容303.2.3 试验方案303.2.4 试验准备30-313.2.5 测试结果及分析31-433.2.6 小结43-45第四章 黄河三角洲咸水区水泥土桩复合地基模型试验研究45-674.1 模型试验基本原理45-484.1.1 量纲分析45-464.1.2 量纲分析的方法46-474.1.3 模型比尺47-484.2 试验方案48-494.3 模型箱研制49-514.4 桩体和复合地基模拟51-524.5 路堤荷载模拟方法52-534.6 模型试验过程及测试53-