Dragload and Downdrag Performances of Inclined Pile Group Embedded in Consolidating Soil

The performance of inclined pile group embedded in consolidating soil under surcharge load was investigated by experiment in comparison with vertical pile group and single pile under the same conditions; dragload, downdrag, and layered soil settlement were measured. A three-dimensional numerical model was built via FLAC3D software, and verified by the experimental results. Influence factors, such as consolidation time, pile spacing, and pile tilt angle were analyzed. The results show that dragload of inclined pile group increases with the increase of consolidation time and pile spacing or the decrease of pile tilt angle. Downdrag of inclined pile group increases with the increase of consolidation time, pile spacing and pile tilt angle.     

浅谈桩的负摩阻力

本文主要分析了桩侧负摩阻力的产生及影响因素,重点介绍了目前常用的桩侧负摩阻力的计算方法。     

两种形式深水桩基施工平台的有限元分析

水上构筑物的大量出现导致了基础施工平台形式的不断发展。通过对两种不同形式的基础施工平台的比较，揭示了两种平台各自的特点。     

Static load test and load transfer mechanism study of squeezed branch and plate pile in collapsible loess foundation

As a special geological phenomenon, the character of collapsible loess foundation is collapsible when penetrated by water. This character leads to the soil losing load bearing capacity largely and may lead to foundation failure. Pile is a popular foundation used in collapsible loess. The squeezed branch and plate pile is a new type of pile developed in recent years and has not be used in a project before. In this paper three squeezed branch and plate piles are tested in collapsible loess after immersion processing. The results may be used for reference in similar construction project, and to provide theoretical references for de- signing of the squeezed branch and plate piles in engineering practice.     

路堤荷载下挤密螺纹桩复合地基沉降现场试验

对新建兴泉铁路黄塘车站挤密螺纹桩复合地基的桩、土沉降及应力进行监测,分析了路堤荷载下桩、土沉降及差异沉降变化规律,桩土应力比与差异沉降关系。结果表明:桩、土沉降及差异沉降均随路堤填土高度的增加而呈线性增大;桩顶和桩间土应力随路堤填土高度的增加均不断增大,且桩顶应力大于桩间土应力;桩土应力比随着桩土差异沉降的增加先增加后减小,最终趋于稳定。结合修正的Terzaghi土拱理论提出了简化桩土应力比随桩土差异沉降变化曲线。现场试验分析结果有助于完善挤密螺纹桩复合地基设计理论,为工程实践提供一定的参考。     

厚层软弱下卧层固结沉降对桩基础变形的影响

在桩基础设计中,由于认识上的问题,往往只考虑持力层是否会破坏,而忽略了特定应用条件下持力层下卧软土固结变形带来的问题。通过工程实例的分析对该问题进行了分析阐述。     

大连地铁旁穿桥梁桩基础数值模拟与现场监测

以大连地铁隧道某区间旁穿高架桥桩基础为背景,利用有限元软件MIDAS/GTS建立了三维数值模型,研究了地面沿隧道轴线方向和横向方向的沉降规律及桥墩的沉降问题。对比数值分析结果和现场监测数据发现:隧道轴线监测点变化趋势都是先微微隆起,再逐渐沉降,最终趋于稳定,测值比模拟值大;地表隧道中心线处沉降值及沉降速度大于轴线两侧地表沉降量及沉降速度,并且随着向两边距离的增大而减小,后达到趋近于零,实测沉降值比数值模拟结果小8 mm,经过60天的观测发现,桥墩的沉降值随隧道的掘进逐渐增大,然后趋于稳定,最大沉降量为8.9 mm,平均沉降速率为1.5 mm/d。     

CFG桩复合地基的研究现状及展望

介绍了CFG桩复合地基的研究现状及存在的问题,并对未来的研究进行了展望.     

某桥墩桩基偏位分析与纠偏实施效果

根据桥墩桩基施工现场的具体情况，通过理论计算，分析了两基桩产生偏位的主要原因。采用卸载止推、反向堆载、挖坑卸荷、强力牵拉等综合纠偏方法对产生偏位的两基桩实施纠偏，经过一个多月的缓慢纠偏使两桩基基本恢复原位，纠偏后经桩身低应变动测（反射波法）检测其桩身完整满足设计要求。     

Test on muddy soil reinforcement by negative pressure and electro-osmosis inside cover-bearing-type bucket foundation for offshore wind turbines

Cover-bearing-type bucket foundation for offshore wind turbines has been paid more and more attention due to its low cost and great bearing capacity. In order to ensure the cover-bearing mode, the muddy soil inside the bucket foundation should be reinforced by some soil consolidation methods, such as negative pressure and electro-osmosis. Firstly, tests were conducted to obtain the reasonable current density. Meanwhile, to improve the electro-osmotic speed and effectiveness, other factors such as intermittent power and layout of electrode, were also studied in the tests. Then, the soil reinforcing tests by negative pressure combined with electro-osmosis were performed for the muddy soil consolidation inside the bucket foundation. The results showed that soil reinforcement by negative pressure was quicker and more obvious during the early phase, and electro-osmotic method can affect more range of soil by rational arrangement of electrodes. Compared with negative pressure, the electro-osmotic method was a continuous and relatively slow process of reinforcement, which was complementary to the negative pressure method. The voltage value of electro-osmosis had little effect on the muddy soil reinforcement inside the bucket foundation, and 1.5 A was chosen as the most reasonable current value for scale model testing in the electro-osmotic method.     

Exothermic process of cast-in-place pile foundation and its thermal agitation of the frozen ground under a long dry bridge on the Qinghai-Tibet Railway

A number of dry bridges have been built to substitute for the roadbed on the Qinghai-Tibet Railway, China. The aim of this study was to investigate the exothermic process of cast-in-place （CIP） pile foundation of a dry bridge and its harm to the stability of nearby frozen ground. We present 3D heat conduction functions of a concrete pile and of frozen ground with related boundaries. Our analysis is based on the theory of heat conduction and the exponent law describing the adiabatic temperature rise caused by hydration heat. Results under continuous and initial conditions were combined to establish a finite element model of a CIP pile-frozen ground system for a dry bridge under actual field conditions in cold regions. Numerical results indicated that the process could effectively simulate the exothermic process of CIP pile foundation. Thermal disturbance to frozen ground under a long dry bridge caused by the casting temperature and hydration heat of CIP piles was substantial and long-lasting. The simulated thermal analysis results agreed with field measurements and some significant rules relating to the problem were deduced and conclusions reached.     

词汇衔接理论在大学英语阅读教学中的应用

英语语篇的词汇衔接手段分为两大类:复现关系和同现关系。本文根据词汇衔接理论的主要内容,阐述了词汇衔接在英语阅读教学中的具体应用。     

超长钻孔灌注群桩承载特性的实验研究和数值分析

采用离心机模型试验和三维有限元模型对天兴洲大桥的超长嵌岩钻孔灌注群桩进行了分析.离心机试验中,根据相似理论,不同的原型材料用不同的指标进行模拟,细砂、桩身、承台分别以天然密度、抗压刚度、抗弯刚度作为指标进行模拟.对土体未开挖阶段、钻孔阶段、混凝土灌注阶段和养护阶段的应力场进行了详细的讨论,并应用ANSYS进行了分析.根据2种方法得到的结果,从荷载沉降曲线、桩身轴力分布和侧向摩阻分布等方面,对比分析了加载和卸载条件下超长钻孔群桩的承载特性.结果表明,有限元计算模型与离心机试验模型沉降观测的结果吻合得很好;桩顶反力的分布规律复杂,与承台的自身刚度、相应的假定和分析方法有关;轴力随着深度先稍微增加,后逐渐减少,并且在岩层中减少的速度远比砂土中快.     

Dynamic response of a beam on a Pasternak foundation and under a moving load

The dynamic response of an infinite beam placed on a Pasternak foundation when the system was subjected to a moving load was investigated. We used the double Fourier transform and its inversion to solve the formulations of the problem. A closed form analytic solution of the beam was obtained by the theorem of residues. We selected a numerical example to illustrate the dynamic response of the beam on Pasternak and Winkler foundations, respectively. We discuss the effect of the moving load velocity on the dynamic displacement response of the beam. The maximum deflection of the beam increases slightly with increased load velocity but increases significantly with reduced shear modulus of subgrade at a given velocity. The maximum deflection of a beam resting on a Pasternak foundation is much smaller than that of a beam on a Winkler foundation.     

Elastoplastic numerical analysis of layered soil foundation under the rectangular shallow footing subjected to vertical load

1 Introduction a Shallow foundation is widely used in civil engineering. Its bearing capacity and settlement are important research subjects in soil mechanics and foundation engineering [1]. Because of the complexity of soil engineering properties, the subject is still under development and improvement. Now the rigid-plastic limit equilibrium method based on the classic plasticity theory is widely used in the engineering practice in China. But soil is not rigid- plastic actually. Hence, the …     

深基坑冻结排桩支护变形性状分析

分析冻结围护技术应用历史和现状，解析、推导其变形方程，并以工程实例为原型，探讨其变形性状特征等，以表明此技术的可靠性和优越性。     

基于混沌序列的数字水印的嵌入和提取方法

提出了一种基于混沌序列的数字水印嵌入和提取方法.因为混沌序列具有随机性,不容易被窃取,从而使得数字作品具有较强的抗攻击性,从而实现信息的隐藏.     

A modified refutation text design: effects on instructional efficiency for experts and novices

Recently, cognitive load theory has been considered within conceptual change research. Although the effectiveness of refutation texts (RT) has been proven, the conceptual change process involved and the influencing factors remain unclear. To contribute to this research, we investigate the efficiency of pupils working with a modified RT design in which the alternative and scientific conceptions are not explicitly contrasted, and we examine the level of learner expertise as a possible influencing factor. We investigated the efficiency based on the scientific conceptions learned and the mental effort invested (reflecting cognitive load) during instruction (N = 195, 9th graders). Only pupils with high prior knowledge (experts) showed low efficiency and higher mental effort when dealing with alternative conceptions. Our results indicate that the experts did not profit from the mental effort they invested in the learning process, whereas the novices seemed to profit from their invested mental effort.     

用电安全实时监测与隐患预警系统设计

随着电气设备使用人数的逐渐增多,用电安全管理水平也亟需提高。传统的用电安全保障主要是通过安全保护装置、人工排查及传统监控报警系统来实现,漏报误报问题较为严重。针对这种情况,提出基于物联网和大数据分析技术的用电安全实时监测与隐患预警系统。结合基于谐波的负载分析、反时限特性实现自适应的预警阈值设置方法和以“数据录波”为基础的数据处理技术,较好地优化了隐患预警算法,提高了系统在线监测及综合分析能力。测试结果表明:系统能根据电气特征参数快速分析出电气安全隐患并实施预警,在对学生宿舍用电进行的负载分析试验中,负载识别准确度达到85%,可以投入实际应用。     

基于SOLIDWORKS电加热器三维建模与数值分析

分析了电加热器的结构特点与SolidWorks软件的三维建模步骤。在几何模型上直接定义了载荷和边界条件,对电加热器温度场与速度场进行了模拟,模拟结果与工程实际吻合较好。探索了有无折流板对电加热器换热的影响,结果显示无折流板的出口温度高于有折流板情况,这对电加热管不利,局部温度过高,长时间工作,容易导致电加热管烧坏。可见利用SolidWorks软件可为电加热器的结构优化与换热等性能的研究提供新的设计手段。