Transport of Gellan Gum Microbeads in Soil Columns of Various Grain Size Distributions

The transport of gellan gum microbeads as potential cell carriers was investigated in horizontal columns packed with different grain size classes of gravel (2–16 mm) and sand (0.25–2 mm). A suspension of microbeads was pulsed into each column for 6 h, followed by injection of water for 42 h. In general, the total amount of microbeads travelling across a given section of the column increased with injection time but decreased towards the column outlet, varying as a direct function of grain size. The results of this study demonstrate the feasibility of the transport of gellan gum microbeads through medium sand to medium gravel across distances up to 110 cm.     

基于粗糙集的载体桩质量核心影响因素分析

针对载体桩质量不容易控制的特点,在剖析载体桩承载机理的基础上,分析了影响载体桩质量的各因素,并引入粗糙集理论,建立了影响因素约简模型。以邯郸地区载体桩工程为例,通过模型约简得出最小的影响因素集,从而确立了影响载体桩质量的核心影响因素,为载体桩的质量预测和控制提供理论依据。结果显示该方法克服了目前人们以主观和定性分析为主的缺点,可信度较高。     

长短桩复合地基设计计算方法探讨

分别从长桩和短桩作用机理两方面阐述了长短桩复合地基的作用机理。以刚性长桩和柔性短桩组合成的长短桩复合地基为例,对常用的长短桩复合地基承载力计算方法之面积加权法和分步叠加法进行了介绍和对比分析,得出两种方法计算结果的一致性,并通过工程实例进行了验证。对长短桩复合地基沉降计算方法之复合模量法和增大系数法进行了介绍,分析了两种计算方法产生误差的原因,给出了一个采用增大系数法计算长短桩复合地基沉降的工程实例,工程实例计算结果与实际观测结果较吻合。建议采用增大系数法计算长短桩复合地基沉降时有必要对加固区桩间土模量增大系数进行适当修正,修正系数的取值范围需通过对大量工程实例进行分析后确定。     

Evaluation of group effect of pile group under dragload embedded in clay

A simple semi-empirical analysis method for predicting the group effect of pile group under dragload embedded in clay was described assuming an effective influence area around various locations of pile group. Various pile and soil parameters such as the array of pile group, spacing of the piles (S), embedment length to diameter ratio of piles (L/D) and the soil properties such as density (γ), angle of internal friction (φ) and pile-soil interface friction coefficient (μ) were considered in the analysis. Model test for dragload of pile group on viscosity soil layer under surface load consolidation conditions was studied. The variations of dragload of pile, resistance of pile tip and the layered settlement of soil with consolidation time were measured. In order to perform comparative analysis, single pile was tested in the same conditions. The predicted group effect values of pile group under dragload were then compared with model test results carried out as a part of the present investigation and also with the values reported in literatures. The predicted values were found to be in good agreement with the measured values, validating the developed analysis method. The model test results show that negative skin friction of pile shaft will reach 80%–90% of its maximum value, when pile-soil relative displacement reaches 2 mm. Foundation item: Project(50679015) supported by the National Natural Science Foundation of China     

高压旋喷桩复合地基承载特性的有限元分析

结合工程实际,运用大型有限元分析软件ANSYS分析了不同桩长、不同桩土模量比和不同桩间距情况下高压旋喷桩复合地基的承载特性.结果表明,该地基存在有效桩长,当桩土模量较合适时,该地基能够发挥最大作用;同时运用ANSYS优化功能,得出了最优桩长、最优桩体弹性模量和最优桩间距,为实际工程提供一些参考.     

螺纹桩在软弱地层中的应用

分析了螺纹桩的受力机理,探讨了螺纹桩单桩承载力的确定方法,指出螺纹桩单桩承载力高、节约材料显著、能充分利用地基土的特性,在软弱地层中的应用优势显著,并通过实际工程实例给予具体说明.     

静压挤密桩在湿险性黄土地基处理中的应用

为了解决水泥土挤密桩施工过程中噪音过大的问题,提出了地基处理的静压挤密桩施工法,并结合工程实际测试了静压挤密桩在湿险性黄土地基处理中应用的效果.测试结果表明,该方法在施工时噪音较小,施工速度高,满足设计要求,此为该地基处理方法的应用和推广提供了依据.     

基于远程监控的基桩检测监督管理实践探索

基桩检测是检验基桩承载力的重要手段,依靠网络对基桩检测实施远程监控,可以规范检测单位的质量行为,确保基桩工程质量控制。文章以江苏省南通市建设工程质量监督站远程监控基桩为例,分析了基桩静载检测行为不规范的主要表现,阐述了基桩静载检测远程监控的实施程序、方法及其配套措施。     

夯扩挤密碎石桩处理液化砂土

目的 消除砂土液化,保证处理深度范围内地基土上下均匀,为液化砂土桩处理探索新的途径.方法 夯扩挤密碎石桩采用相同的夯击能量和贯入度控制桩体质量,以高能量施工设备进行孔内夯击填料,振动和挤密桩底和桩间土,使松散砂土颗粒重排,提高砂土的承载力和压缩模量.笔者对比分析夯扩挤密碎石桩在沿海高速路基工程上的应用实例.结果 采用夯扩挤密碎石桩复合加固地基,可提高砂层标贯锤击数30%,消除砂土液化现象,提高地基承载力,与振冲桩相比节省造价约20%.结论 夯扩挤密碎石桩方法工艺简单,施工质量易保证,节约水资源;夯扩挤密碎石桩对于公路路基工程,具有广阔的应用前景,开辟了处理砂土液化的新途径.     

盐渍化软弱土地基处治措施对比分析

为了综合提高西北地区盐渍化软弱土地段公路地基处理的工程质量,以嘉—安一级公路盐渍化软弱土地段的地基处治项目为工程依托,通过MARC有限元数值计算分析、现场实际监测数据结果以及地基处治措施的社会经济效果评价,研究了适用于西北盐渍化软弱土地基处治的合理措施.结果表明,在处理该特殊土地基时,水泥粉喷桩、强夯置换、振动沉管挤密砂石桩都符合规范要求;从处治效果上来看,后两者的效果要优于水泥粉喷桩,振动沉管挤密砂石桩的效果最好;从社会经济效益评价结果来看,强夯置换在处理盐渍化软弱土地基时的费用最低,最省时,经济效果明显.