Behavior of transporting pipeline sections without and with hydrogen exposure based on full-scale tests

Pipeline transport of hydrogen is one of today’s economic and environmental challenges.In order to find safe and reliable application of both existing gas and build new pipelines,it is essential to carry out tests on full-scale pipeline section,including the potentially more dangerous places than the main pipe,the girth welds.For the investigations,pipeline sections of P355NH steel with girth welds were prepared and exposed to pure hydrogen at twice the maximum allowable operating pressure for 41 days.Subsequently,full-scale burst tests were carried out and specimens were cut and prepared from the typical locations of the failed pipeline sections for mechanical,and macro-and microstructural investigations.The results obtained were evaluated and compared with data from previous full-scale tests on pipeline sections without hydrogen exposure.The results showed differences in the behavior of pipeline sections loaded in different ways,with different characteristics of the materials and the welded joints,both in the cases without hydrogen exposure and in the cases exposed to hydrogen.

Analysis of the Application of Static Load Test in Bridge Bearing Capacity Testing

This article uses real engineering projects as examples to analyze how static load test technology is applied in testing the bridge-bearing capacity.The analysis covers aspects such as testing section layout,test load and efficiency coefficient,loading plan,evaluation optimization,test result modification,and result evaluation.The aim is to support the accurate detection and evaluation of bridge-bearing capacity.

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.

Application of bi-directional static loading test to deep foundations

Bi-directional static loading test adopting load cells is widely used around the world at present, with increase in diameter and length of deep foundations. In this paper, a new simple conversion method to predict the equivalent pile head load-settlement curve considering elastic shortening of deep foundation was put forward according to the load transfer mechanism. The proposed conversion method was applied to root caisson foundation in a bridge and to large diameter pipe piles in a sea wind power plant. Some new load cells, test procedure, and construction technology were adopted based on the applications to different deep foundations, which could enlarge the application scopes of bi-directional loading test. A new type of bi-directional loading test for pipe pile was conducted, in which the load cell was installed and loaded after the pipe pile with special connector has been set up. Unlike the conventional bi-directional loading test, the load cell can be reused and shows an evident economic benefit.

Technical Analysis of Highway Bridge Static Load Test

Highway bridges are an important part of the transportation industry and can promote social economic construction and development.In actual operation,highway bridges are often damaged due to overload and natural factors,which tend to affect the safety and shorten the service life of these bridges.Assessing the overall state and performance of highway bridges is therefore a key element.Static load test,which is a type of sustainable detection experiment,has many advantages,including low cost,high efficiency,and high accuracy.In this paper,the bridge structure is analyzed through the application of theoretical calculations and relevant comparisons,so as to judge the operating state of the bridge.

Static Load Test Detection of Continuous Rigid- Frame Railway Bridge

The quality of the continuous rigid-frame railway bridge is related to the safety of train operation,so it is necessary to test its stiffness,strength,and other indicators.Static load test is a common technique for bridge inspection.This article summarizes the purpose of the static load test for a continuous rigid-frame railway bridge,including the required equipment,operation methods,etc.,and lists examples to analyze the operation process and precautions of static load test,hoping to provide reference information for relevant personnel.

Mechanical properties of rock under coupled static-dynamic loads

Rock drilling machine,INSTRON testing system,and SHPB device are updated to investigate the characteristics of rocks at great depth,with high loads from overburden,tectonic stresses and dynamic impacts due to blasting and boring.It is verified that these testing systems can be used to study the mechanical properties of rock material under coupled static and dynamic loading condition and give useful guidance for the deep mining and underground cavern excavation.Various tests to determine the rock strength,fragmentation behavior,and energy absorption were conducted using the updated testing systems.It is shown that under coupled static-dynamic loads,if the axial prestress is lower than its elastic limit,the rock strength is higher than the individual static or dynamic strength.At the same axial prestress,rock strength under coupled loads rises with the increasing strain rates.Under coupled static and dynamic loads,rock is observed to fail with tensile mode.While shear failure may exist if axial prestress is high enough.In addition,it is shown that the percentage of small particles increases with the increasing axial prestress and impact load based on the analysis of the particle-size distribution of fragments.It is also suggested that the energy absorption ratio of a specimen varies with coupled loads,and the maximum energy absorption ratio for a rock can be obtained with an appropriate combination of static and dynamic loads.

Effects of Microstructure on Quasi⁃Static Transverse Loading Behavior of 3D Circular Braided Composite Tubes

The effects of microstructure on quasi-static transverse loading behavior of 3D circular braided composite tubes were studied. Transverse loading tests were conducted. Transverse load-deflection curves were obtained to analyze the effects of braiding parameters including the braiding angle, the wall thickness, and the diameter on the transverse loading of 3D circular braided composite tubes. Breaking loads, moduli and strengths had also been used to describe the transverse loading behaviors. The failure morphologies were shown to reveal damage mechanisms. From the results, the increase in braiding angle, wall thickness and diameter increases the ability of anti-deformation and breaking load of braided tubes. The breaking load of specimen with a braiding angle of 45° is about 1.68 times that of specimen with a braiding angle of 15°. The breaking load of specimen with 4 layers of yarns is about 2.15 times that of specimen with 2 layers of yarns. The breaking load of the tube with a diameter of 25.5 mm is about 2.39 times that of the tube with a diameter of 20.5 mm.

基于SmartRock传感技术的道砟静力循环平板载荷试验研究

基床道砟在交通荷载重复作用下的位移变形机制尚不清晰,为了研究道砟在静力循环荷载作用下的沉降规律和道砟颗粒的位移旋转特性,利用自行设计的静力循环平板试验模型装置,对道砟填料开展不同幅值下的静力循环平板载荷试验,结合SmartRock无线传感器技术分析道砟层不同位置颗粒接触变形特性,揭示循环加卸载过程中道砟沉降及旋转特性。结果表明:低、中、高3种幅值下的累积塑性变形分别为2.92、3.91、12.37 mm,且低幅值和中幅值工况的累积塑性变形量为高幅值工况的22.94%、30.71%,表现为道砟承载塑性变形对基底高压力敏感性高;建立峰值沉降量与循环次数和荷载幅值之间数学模型,可较好预测经过多次循环后道砟的峰值沉降量;在静力循环加卸载过程中,低幅值和中幅值工况的x、y轴转角的最大值分别为高幅值工况的22.19%、34.90%和32.45%、39.55%,颗粒绕x、y轴转动的概率远大于z轴,在一个方向的转动响应弱,必然会在另一个方向的转动响应强,且循环荷载作用是道砟填料磨损严重的重要原因之一。

钢-混工字组合简支梁桥静动载试验及冲击系数研究

近年来钢-混工字组合简支梁桥因其能充分发挥不同材料特性而被广泛应用,但评价动力特性的重要指标———冲击系数的计算尚缺少相关试验积累和理论研究。以一座新建钢-混工字组合简支梁桥为依托,详细介绍了该桥的静载试验以及脉动、跑车、跳车等动载试验过程,探讨了此类结构冲击系数的试验计算值,并与各规范计算值进行了对比。结果表明:该桥整体刚度好,承载安全度高;冲击系数的试验计算值多数大于各规范计算值,采用规范设计相对不安全;跨中冲击系数试验计算平均值等于我国规范《公路桥涵设计通用规范》(JTG D60—2015)计算值,但也出现了试验值大于规范值的情况。因此,今后进行高速公路30m跨径钢-混工字组合简支梁桥设计时,应对桥梁跨中冲击系数适当放大。

深厚火山灰堆积区大直径灌注桩水平静载试验研究

富含火山灰土层具有特殊的物理力学性质和工程特性,其水平抗力系数的比例系数m的取值不清,途径该地区的高速铁路桩基水平承载特性不明。为此开展了火山灰堆积地区高速铁路桥梁单桩的水平静载试验,分析了该地区桩基的水平承载变形特性,综合分析了不同行业规范对m值折减系数的具体要求,开展了富含火山灰土层m值的取值研究。研究结果表明:富含火山灰土层m值随水平荷载的增大呈非线性衰减,随水平位移的增大而近似呈幂函数形式衰减。获得了单桩水平临界荷载和极限水平承载力,并提出了考虑工作折减系数后的火山灰粉质黏土m的取值建议。研究成果可为我国富含火山灰土层m的合理取值和该地区高铁桥梁桩基水平承载力计算、安全评估提供重要参考。

大直径超长灌注桩承载特性研究

为明确黄河中下游地区粉土、粉细砂地层中长大桩基承载特性及荷载传递机理,依托实际工程,结合室内土工试验、现场原位测试和数值模拟手段开展了系统性研究。采用自制的大型直剪仪开展了不同含水率条件下粉土-混凝土界面直剪试验,设计拉压锚法加载反力装置实现了桥梁钻孔灌注桩36000 kN大吨位加载,基于直剪试验和静载试验结果,运用ABAQUS试算拟合土体与界面参数,进一步研究了基桩水平承载能力。结果表明:粉土-混凝土界面剪切强度随粉土含水量的增大而减小,粉土含水量的增加会显著减弱土体与混凝土结构界面的剪切作用。粉土-混凝土界面剪切强度包络线基本符合摩尔库仑强度理论,土体含水量与界面的黏聚力和摩擦角呈负相关变化规律。在建立的桩土竖向静载试验模型与原位测试数据吻合性良好的前提下,开展桩基水平承载力数值模拟,发现所得结果与设计方案基本相当,满足规范要求,文中相关结论可为相关工程设计提供借鉴。

基于BIM的桥梁荷载试验可视化研究

为保障桥梁结构安全,增强荷载试验布载现场与检测结果的可视化,以某先张法预应力简支空心板梁桥为例,结合有限元分析与BIM技术,提出并采用Revit+Civil模式构建桥梁荷载试验的三维可视化参数模型体系。在静载工况下,对各测试截面的应力、挠度理论数据进行提取,绑定参数,实现了桥梁荷载试验测点位置、测试过程及测试结果的三维可视化和准确表达。

静载试验在水利工程基桩检测中的应用研究

本文旨在探索静载试验在水利工程基桩检测中的应用。本文介绍了静载试验的主要方法和过程,并详细叙述了该试验在水利工程基桩检测中的应用,简要总结了静载试验得出的关键结果和发现,涵盖了基桩的承载力、变形特性以及安全性等方面。本文强调了该研究的主要结论和意义,并强调了在水利工程基桩设计和施工中使用静载试验的重要性。

水运工程码头竖向静载试验中不确定性因素分析

文章结合文献分析法对水运工程码头竖向静载试验中的不确定性因素、不确定性因素对竖向静载试验的影响及其控制策略方面进行了研究。研究结果显示,材料特性、结构尺寸、环境条件以及测试设备和方法是水运工程码头竖向静载试验中的不确定性因素。针对这些因素,从材料质量控制、结构设计优化、环境适应性设计以及测试设备与方法的标准化方面提出了控制措施。

软土地区大直径复合后注浆超长灌注桩承载特性研究

由于复合后注浆超长灌注桩荷载传递规律尚不明晰,因此开展了软土场地超长灌注桩大吨位静载试验,系统分析了直径为1.0 m、桩长为110 m超长桩的荷载-位移(Q-s)关系,桩身轴力、桩侧摩阻力的变化特性。研究结果表明:Q-s曲线多呈缓变型特征,在极限荷载作用下,灌注桩身出现了一定的塑性变形;复合后注浆作用使得桩侧摩阻力发挥所需相对位移变小,而桩端阻力则受影响较小,在加载至极限状态下其端阻比仍不足2%,表明场地内超长灌注桩呈摩擦桩特性;此外,桩端阻力和桩端附近的桩侧摩阻力存在显著的耦合效应,也就是桩端后注浆促使桩端附近桩侧摩阻力出现了一定的增长。该研究成果可为超长灌注桩的理论研究与工程实践提供参考。

预应力混凝土连续箱梁单梁模型与梁格模型有限元对比分析与研究

以某预应力混凝土变截面连续箱梁为研究对象,采用MIDAS Civil对其分别进行单梁模型和梁格模型的内力计算,通过两种模型的计算结果与静载试验实测结果的对比分析,探究基于两种模型计算变截面连续箱梁受力状态和结构变形的可靠性和合理性。研究结果表明:在恒载和设计荷载作用下,对于预应力混凝土连续箱梁,在采用单梁模型和梁格模型进行计算分析时,两种模型的计算结果基本相同;在偏载作用下,通过静载试验计算结果分析,梁格模型内力计算结果比单梁模型内力计算结果均偏小,并且两种模型误差超过了5%,对结果影响评价的准确度不容忽略;梁格模型能够准确地计算连续箱梁在横桥向的应力分布、应力大小和结构变形,相较于单梁模型,梁格模型更能反映结构的空间受力特性,表明采用梁格法计算分析变截面连续箱梁桥更符合工程要求。

预制管桩在黏土地质的应用可行性及承载性能研究

本文旨在探讨预制管桩在黏土地质条件下的应用可行性及其承载性能。根据预制管桩设计允许荷载的50%、100%、150%、200%设置了4种循环加载模式,通过锚桩横梁反力装置对试桩施加不同等级的竖向循环压载,观察并分析加载过程中试桩的沉降响应,最终估算出桩基的极限荷载。研究结果表明,在200吨超载条件下,预制管桩在黏土地质中表现出良好的承载性能;根据竖向荷载的加载时间与试桩的沉降量之间的关系,估算出了桩基的极限荷载为262吨。这一结果远高于设计允许荷载(100吨),进一步验证了预制管桩在黏土地质中的高承载能力和稳定性。

NMR-based damage characterisation of backfill material in host rock under dynamic loading

It is not uncommon that backfill material used in underground mining being exposed to repetitive dynamic stresses induced by blasting operations or rockburst events. Understanding the strength and fracture evolution of backfilled stopes is critical to maintain the long-term stope stability and ensure safe mining activities. This paper aims to study the damage evolution of the backfill material and its host rock behaviour under three-dimensional(3D) dynamic loading. Using a true-triaxial testing machine, multiple samples of backfill material enclosed by country rock were fabricated and tested under various dynamic loadings with different true-triaxial confining stress conditions. In addition, the nuclear magnetic resonance(NMR) measurement was conducted on the samples before and after exerting static and dynamic loading to obtain their porosity distribution changes. The experiment results suggested that with the increase of the dynamic loading, the porosity of the backfill sample goes through a two-stage process,which shows a slightly linear decrease and then followed by an exponential increase. The research findings can help understand the damage mechanism and fracture development of backfilled stopes and its host rock in deep underground mines, which are constantly subject to the combination of 3D static confining stress and dynamic loading.

Destructive field tests on mobilization of end resistance of cast-in-situ bored piles

A series of well-designed full-scale destructive load tests were conducted on six bored piles to investigate the influence of loose debris at the pile tip on end resistance. The results show that soft debris below the pile tip will weaken the mobilization of end resistance. The ultimate tip resistance of post-grouted pile is 2.05 times that of the pile without post-grouting and the ultimate tip resistance in the second load cycle is 2.31 times that of pile in the first load cycle. The relationship between unit end resistance and displacement follows a linear model and a bilinear mode in the first load cycle and the second load cycle, respectively, whereas the unit end resistance-displacement response of post-grouted bored pile can be simulated using a bilinear mode. The critical end resistance ranges between 2 000 kN and 3 000 kN and the critical displacement ranges between 2.5 mm and 4.5 mm in the bilinear mode. As for piles rested on moderately-weathered peliticsiltstone, the socketed length has no effect on the end resistance because of the existence of loose debris.