共查询到20条相似文献，搜索用时 46 毫秒
1.
Open-ended pipe piles are commonly driven into the seabed to support offshore platforms. This paper presents a case of practical offshore driven pile installation experiences associating with premature refusal. Pile drivability and capacity are analyzed using sufficient driving records. Dynamic loading tests were performed three months after the driving in order to determine the pile capacity after refusal. The test results are detailed in this paper compared with back analysis of measured pile driving records. Empirical equations are provided to predict soil resistance during driving and after setup according to the driving records and dynamic loading tests. Analyzing this practical engineering case is hoped to lead to a better understanding of pile driving, especially when premature refusal occurs. The sufficient details of the engineering data in this paper are also expected to enrich the engineering experience and literature of offshore piles in offshore engineering. 相似文献
2.
Samuel G. Paikowsky Robert V. Whitman Mohsen M. Baligh 《Marine Georesources & Geotechnology》2013,31(3):213-230
Abstract Open‐pipe piles are widely used for offshore structures. During the initial stage of installation, soil enters the pile at a rate equal to the pile penetration. As penetration continues, the inner soil cylinder may develop sufficient frictional resistance to prevent further soil intrusion, causing the pile to become plugged. The open‐ended pile then assumes the penetration characteristics of a closed‐ended pile. The mode of pile penetration significantly alters the soil‐pile interaction during and after installation. This affects the ultimate static bearing capacity (mainly in granular materials), the time‐dependent pile capacity (in clays), and the dynamic behavior and analysis of the piles. Following a summary demonstrating the effects of pile plugging, a review of the common view of offshore pile plugging is undertaken. The interpretation of plugging by referring to the average plug length has led to the erroneous conclusion that in most piles significant plugging action does not occur. Establishment of an analogy between soil samplers and open‐ended piles enabled correct identification of plugging by referring to the incremental changes in plug length. Examination of case histories of plugging of offshore piles revealed that beyond a certain penetration depth‐to‐diameter ratio, most piles are plugged. 相似文献
3.
Jingbo Su Jianfeng Li Ruihu Zhu Wanggen Qin Qiu Zhai 《Marine Georesources & Geotechnology》2016,34(7):689-702
To assess the impact of pile driving on adjacent submarine pipelines during the reconstruction of a pier berth, the local damage model of submarine pipelines is established to explore the safety thresholds of the particle peak velocity and horizontal displacement. The results are analyzed and adjusted by the existing standards and the corresponding literatures. Then, a three-dimensional numerical model is presented to assess the feasibility of the construction of piles by the obtained safety limits, in which the nonlinear behavior of the soil and stress–seepage coupling analysis are considered. After the construction, the safety of submarine pipelines is rechecked by the measured value of the particle peak velocity and horizontal displacement. Meanwhile, the propagation law of vibration, the horizontal displacement of underground soil, and the pore pressure during pile driving are explored. The results indicate that the construction of piles of 2# mooring pier did not cause damage to adjacent submarine pipelines. However, the construction of piles of 1# mooring pier which is nearer may cause damage to submarine pipelines. 相似文献
4.
AbstractAn experimental study of the performance of concrete pipe piles during installation under different penetration speeds and static load tests on the piles in sand is presented. The applied jacking force, the amount of pile penetration, length of soil plug formed and ultimate bearing capacity were measured during the model tests. The results showed that the concrete pipe piles were partially plugged and the behavior of the soil plug was significantly affected by the penetration speed. The lower the penetration speed, the larger the soil plug formed which in turn leads to a greater ultimate bearing capacity. The size of soil plug can be evaluated by the m value defined as the ratio of the volume of the soil plug to that of the penetrated pile wall. The relationship between the m value and the penetration speeds can be used to estimate the amount of soil plug and the depth of penetration for an open-ended concrete pipe pile jacked into sand. 相似文献
5.
Liqiang Sun Yandi Wang Shuwang Yan Jian Chu Xiaoqiang Liu 《Marine Georesources & Geotechnology》2018,36(6):709-721
The super-long and large-diameter steel pipe piles are often adopted for the construction of offshore oil platforms in deep sea. One constructability issue related to driving heavy pipe piles is the pile running. The term pile running refers to the quick penetration of a pile into the seabed as a result of its high self-weight and low resistance from the seabed. The unexpected pile running can cause the steel wire of the hammer to break or even the loss of the hammer. A case study of pile running at an oil platform is introduced in this paper. A simplified theoretical method is proposed to explain the mechanisms of the pile running in this case. A factor of friction degradation is proposed to calculate the dynamic skin friction from the static ultimate skin friction of surrounding soil. The comparisons between the predictions to the case history show that the proposed simplified method can be used to predict the pile running condition. 相似文献
6.
辽河三角洲潮道沉积物为软弱淤泥质土，管桩在波流荷载作用下的弹性变形或振动，可以导致潮道软土强度衰减并发生变形位移，随着悬臂段加长和波流荷载振动作用，下部扮土会自上而下发生液化。简单管桩的抗倾验算可以按照波流力与被动土压力的作用力矩分析，并考虑到海底的冲刷淘空深度。管桩打入下卧高强度粉土时，在保证打入深度的同时，应适当增大管桩的强度，加大管桩自振周期与波浪周期的差值。 相似文献
7.
AbstractIn this article, the drivability of stepped and tapered offshore piles with the same length and volume has been investigated under hammer blows. To justify the obtained results from field testing and numerical methods, this pile driving procedure has been analyzed and discussed with wave propagation mechanism. It will be shown that tapered pile can be confidently idealized as a number of prismatic segments connected rigidly to each other. This is an interesting finding that fully tapered or stepped piles have a better performance in pile driving and enable users to apply simple one dimensional numerical analysis for simulating pile drivability. 相似文献
8.
钢管斜桩是潮间带风电的常用基础形式,常采用吊打沉桩的方式。文章针对潮间带吊打沉桩方式的难点开发吊打导向装置,并总结沉桩参数的确定方法。该导向装置包括定位桩、定位架和调向限位架,总体平面布局为六边形,可一次定位并完成整个风电基础的基桩施工,既能可靠保证桩的施工精度,又能极大地提高施工效率和降低安全风险;在应用该施工关键装备时,采用GRLWEAP打桩分析功能确定桩顶动荷载,采用有限元软件建立导向装置有限元模型,对导向装置和沉桩参数进行分析,从而实现斜桩顺利沉桩的目的。该装置和方法已成功应用于越南朔庄一期海上风电场项目,为潮间带风电钢管斜桩吊打施工提供沉桩装备和方法经验。 相似文献
9.
AbstractThe ground vibrations during pile driving operation have a drastic potential to undermine the surrounding structures both in land and reclaimed land. Particularly, reclaimed land necessitates ample application of pile driving due to the weak land condition. To prevent the structural damage, attenuation of the ground vibrations to an allowable level through active isolation of circular open trench is the scope of this study. In this research, finite element simulations of continuous impact pile driving process from the ground surface was executed with particular attention to the pile-soil interaction, and thereby, the efficiency of open trench application in attenuation of the unsafe distance of different structures was surveyed using the vibration sensitivity degree. Regarding the crucial parameters of an open trench (depth, width, and location), it was concluded that a sufficient high depth can attenuate the unsafe distance up to 68%, the trench width variations are less effective, and an average pile-trench distance is the most efficient option. The excavation volume was also concluded as another crucial parameter in open trench design which takes all three parameters into account. The trench depth equal to the pile’s maximum critical depth of vibration was inferred for an optimum design. 相似文献
10.
AbstractThis study investigates the impact of pile cap size, soft layer thickness and pile strength on load transfer and settlement behaviors of embankments supported by floating and fixed T-shaped deep cement mixing piles and conventional DCM piles under volume control. Preliminary investigation is performed by a series of small-scale physical model tests. The results reveal that the differential settlement can be substantially reduced with an enlarging pile cap as a result of larger embankment load transferred to the piles. The extended numerical analysis results demonstrate that the pile efficacy is related to the individual pile bearing capacity, which, in turn, depends on the pile cap size. The soft layer thickness has an insignificant effect on differential settlement but a significant effect on average settlement, while the pile strength plays an important role in differential settlement only when the cap size is not very large. Shape factor of at least 3.0 is recommended to ensure the reduction in differential settlement and minimize the effect of the change in pile strength. 相似文献
11.
近年来海上工程的规模越来越大,为了满足工程需要,桩基设计常常采用大直径,大长度的钢管桩。打桩过程是个相当复杂的过程,不仅涉及到几何非线性、材料非线性、边界非线性,而且是个动力过程。有限元法在处理打桩分析方面具有很强的优势,采用PLAXIS对不同条件下的打桩问题进行了动力模拟分析。分析显示在打桩过程中,桩端土体会产生较大的水平位移和竖向位移,桩端土体和靠近桩端的部分土塞内会产生较大的超孔隙水压力。在砂土中,停锤较短时间也会使孔压迅速消散,这也是打桩中间的停锤会造成后续打桩困难的主要原因。 相似文献
12.
Long steel piles with large diameters have been more widely used in the field of ocean engineering.Owing to the pile with a large diameter,soil plug development during pile driving has great influences on pile driveability and beating capacity.The response of soil plug developed inside the open-ended pipe pile during the dynamic condition of pile-driving is different from the response under the static condition of loading during service.This paper addresses the former aspect.A numerical procedure for soil plng effect prediction and pile driveability analysis is proposed and described.By taking into consideration of the pile dimension effect on side and tip resistance,this approach introduces a dimensional coefficient to the conventional static equilibrium equations for the plug differential unit and proposes an improved static equity method for the plug effect prediction.At the same time,this approach introduces a simplified model by use of one-dimensional stress wave equation to simulate the interaction between soft ping and pile inner wall.The proposed approach has been applied in practical engineering analyses.Results show that the calculated plug effect and pile driveability based on the proposed approach agree well with the observed data. 相似文献
13.
Large-scale field tests were conducted to study set-up effect in open-ended prestressed high-strength concrete pipe piles jacked into stratified soil. Four open-ended prestressed high-strength concrete pipe piles with 13 and 18 m in embedment depth were fully instrumented with fiber Bragg grating sensors and installed. Several restrike dynamic tests were performed on each test pile, with the time interval from 21.5 to 284 hours after installation. Static loading tests (SLTs) were later performed on each test pile at 408 hours after installation to substantiate the dynamic tests. Changes with time in pile bearing capacity and in the shaft and toe resistances were studied based on the results of the pile tests. The development of shaft resistance set-up in different layers was studied in particular. It was found that set-up effect in the shaft resistance is significant and the toe resistance increment was minor. The overall set-up factor of total bearing capacity was found to range from 0.09 to 0.53, and the set-up effect of friction pile is much larger than the end bearing pile. More significant set-up in shaft resistance was observed in fill and alluvium layer. The dimensionless set-up factor A for shaft resistance in marine deposits ranges from 0.5 to 1.43, and it contributes the most to the shaft resistance as the shaft resistance in marine deposits is higher. 相似文献
14.
大直径超长桩的可打入分析是海洋平台打桩施工顺利进行的重要保障,土塞是否闭合的判断对于桩基可打入性分析具有较大的影响,因此,合理准确的土塞判断结果对提高桩的可打入分析的准确性具有重要的意义。以现场静力触探(CPTU)试验数据为依据,采用孔扩张理论推导了基于CPTU测试结果的桩端土的极限承载力计算公式;在求解桩端土体承载力时考虑了管桩与土体的刚度差异,同时考虑到打桩过程中的土体扰动。采用Randolph推荐的方法得到了土塞阻力,将两者进行比较,进而判断土塞的状态。通过实际工程的实测数据,对各个土层的土塞状况进行了判别,并根据判别情况采用波动方程的方法对桩基的可打入性进行了分析,将预测结果和现场的打桩记录进行了比较。计算结果显示,提出的方法与实测结果更为接近,有效地提高了桩的可打入性的预测精度。 相似文献
15.
海上复杂地质条件下大直径钢管桩时效性试验研究 总被引：1，自引：1，他引：0
通过对3根海上复杂地质条件下的大直径钢管桩采取高应变初打与不同休止时间复打相结合的试验方法,得到不同休止时间钢管桩承载力、侧阻力及端阻力大小,以此对不同桩侧土及持力层对钢管桩时效性的影响进行了研究。研究结果表明:1)钢管桩承载力时效性现象明显,且随时间增长迅速; 2)钢管桩侧阻力的恢复系数远大于端阻力; 3)桩侧黏性土强度的恢复是钢管桩侧阻力增加的主要原因; 4)砂土层虽提供的侧阻力较大,但其对侧阻力增长的贡献不如黏性土; 5)持力层越硬,端阻力与承载力的恢复性越差。 相似文献
16.
鉴于海底管道的服役水深越来越深,主要采用犁式挖沟机对预铺设于海床之上的海底管道采取后挖沟的方式将海底管道埋设于海床之下,以保护其免受不必要的损伤。针对后挖沟深度H是海底挖沟机的重要设计参数,也是影响管道悬跨的重要因素的问题,对SMD(UK)犁式挖沟机展开参数优化,确保作业过程中悬跨段管道在外部静水压力作用下,海底管道不会发生屈曲破坏。采用ABAQUS软件,分别建立了作业前和作业中两种工况下的悬跨模型,分析机械手对接触部分管道的损伤,结果显示,作业中的机械手对悬跨管道的损伤更大;同时,建立了作业中不同管径下,后挖沟深度对管道损伤的安全裕量关系曲线。进一步,结合作业中不同挖沟深度下的管跨段屈曲数值模型,对处于外部静水压力作用下的悬跨管的屈曲失效展开分析,结果显示,随着后挖沟深度的加大,不同管径下的悬跨段管道局部出现塑性压溃的临界压力值不断降低;管道外径的增大,降低了同一后挖沟深度下发生屈曲失效的压力值。最后,在后挖沟深度与外部静水压力组成的区域内,建立屈曲失效临界关系曲线,并划分出工作区和压溃区,为深海管道后挖沟埋管的施工提供工程参考。 相似文献
17.
18.
Energy transfer ratio is the basic-factor affecting the level of pipe damage during the impact between dropped object and submarine pipe. For the purpose of studying energy transfer and damage mechanism of submarine pipe impacted by dropped objects, series of experiments are designed and carried out. The effective yield strength is deduced to make the quasi-static analysis more reliable, and the normal distribution of energy transfer ratio caused by lateral impact on pipes is presented by statistic analysis of experimental results based on the effective yield strength, which provides experimental and theoretical basis for the risk analysis of submarine pipe system impacted by dropped objects. Failure strains of pipe material are confirmed by comparing experimental results with finite element simulation. In addition, impact contact area and impact time are proved to be the major influence factors of energy transfer by sensitivity analysis of the finite element simulation. 相似文献
19.
The high under-water sound pressure levels (SPLs) produced during pile driving to build offshore wind turbines may affect harbor porpoises. To estimate the discomfort threshold of pile driving sounds, a porpoise in a quiet pool was exposed to playbacks (46 strikes/min) at five SPLs (6 dB steps: 130–154 dB re 1 μPa). The spectrum of the impulsive sound resembled the spectrum of pile driving sound at tens of kilometers from the pile driving location in shallow water such as that found in the North Sea. The animal's behavior during test and baseline periods was compared. At and above a received broadband SPL of 136 dB re 1 μPa [zero-peak sound pressure level: 151 dB re 1 μPa; t90: 126 ms; sound exposure level of a single strike (SELss): 127 dB re 1 μPa2 s] the porpoise's respiration rate increased in response to the pile driving sounds. At higher levels, he also jumped out of the water more often. Wild porpoises are expected to move tens of kilometers away from offshore pile driving locations; response distances will vary with context, the sounds' source level, parameters influencing sound propagation, and background noise levels. 相似文献
20.
The static drill rooted nodular (SDRN) pile is a new type of precast pipe pile with equally spaced nodes distributed along the shaft and wrapped by the surrounding cemented soil. In this paper, the longitudinal dynamic response of the SDRN pile embedded in layered soil is investigated with respect to the complexity of the pile body structure and the pile–soil contact condition. First, the shear complex stiffness transfer model is used to simulate the radial inhomogeneity of the surrounding soil. Then, the governing Equations of the pile–soil system subjected to longitudinal dynamic loading are established. The analytical solution for the dynamic response at the pile head is obtained by the shear complex stiffness transfer method and the impedance function transfer method. The degenerate case of the present solution is compared with the published solution to verify its reliability, and the complex impedance of the SDRN pile is compared with that of the precast pipe pile and the bored pile. Finally, a parametric study is conducted to investigate the influence of pile–soil parameters on the complex impedance at the pile head within the low frequency range concerned in the design of the dynamic foundation. 相似文献