Axial compressive response of large-capacity helical and driven steel piles in cohesive soil
Axial compressive response of large-capacity helical and driven steel piles in cohesive soil
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DOI：
10.1139/cgj-2012-0331
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发表时间：
2015-02-01
影响因子：
3.6
通讯作者：
El Naggar, Hesham
中科院分区：
文献类型：
--
作者：
Elkasabgy, Mohamed;El Naggar, Hesham
大容量螺旋桩的轴向压缩性能是非常重要的，因为它们可以提供一个有效的替代传统的打桩系统在许多应用中，如在石油加工设施，输电塔，和工业建筑。本文介绍了7个全尺寸轴向压缩载荷试验的结果进行了6.0和9.0米的大容量螺旋桩和6.0米打入钢桩。研究结果对于定性和定量分析粘性土中大承载力螺旋桩的工作特性具有重要意义。测试桩是封闭端的钢轴，外径为324 mm。测试螺旋桩是单螺旋或双螺旋，螺旋直径为610 mm，螺旋间距为螺旋直径的1.5倍至4.5倍。使用现场和实验室测试方法确定了试验场地的地下土壤特性。6.0 m桩在安装后2周进行测试，而9.0 m桩在安装后9个月进行测试。为了更好地了解试桩的性状，给出了荷载-沉降曲线。提出了一种估算大承载力螺旋桩极限承载力的极限承载力准则。试验螺旋桩的极限阻力是打入桩的1.2-1.8倍。对大承载力螺旋桩的荷载传递机理进行了研究，发现无论螺旋间距与螺旋直径比大小如何，沉桩过程中土体扰动对桩的破坏机理有显著影响。反算了活化土强度参数，并与估计的原状土强度参数进行了比较。
The axial compression performance of large-capacity helical piles is of significant interest because they can offer an efficient alternative to conventional piling systems in many applications such as in oil processing facilities, transmission towers, and industrial buildings. This paper presents the results of seven full-scale axial compression load tests conducted on 6.0 and 9.0 m large-capacity helical piles and a 6.0 m driven steel pile. The results are considered essential to qualify and quantify the performance characteristics of large-capacity helical piles in cohesive soils. The test piles were close-ended steel shafts with an outer diameter of 324 mm. The test helical piles were either single or double helix, with a helix diameter of 610 mm and interhelix spacing that varied between 1.5 and 4.5 times the helix diameter. The subsurface soil properties at the test site were determined using field and laboratory testing methods. The 6.0 m piles were tested 2 weeks after installation, while the 9.0 m piles were tested 9 months after installation. The load-settlement curves were presented to better understand the behaviour of test piles. An ultimate capacity criterion was proposed to estimate the ultimate load of large-capacity helical piles. The test helical piles developed ultimate resistances up to 1.2-1.8 times that of the driven pile. The load-transfer mechanisms of large-capacity helical piles were studied, and it was found that soil disturbance during pile installation had a significant effect on the pile failure mechanism regardless the value of the interhelix spacing to helix diameter ratio. The mobilized soil strength parameters were back-calculated and compared with the estimated intact soil strength parameters.