大直径深长桩泥岩侧摩阻力试验研究——以吉林省龙华松花江特大桥工程试桩为例

Testing of skin friction of large diameter deep piles in mudstone: A case study of the test piles for the Songhua River large bridge in Jilin Province

摘要:

泥岩地基中泥岩的桩侧摩阻力设计参数比较缺乏。通过对吉林省龙华松花江特大桥工程试桩的自平衡静载试验分析，并结合室内桩和泥岩接触中型剪切摩擦试验，揭示了该地区泥岩地基中大直径深长灌注桩泥岩侧摩阻力作用机制及承载特征，得出了一些对泥岩地基中钻孔灌注桩的设计和深入研究具有指导意义的结论。结果表明：大直径深长桩桩端阻力分担的荷载只占总承载力的一小部分，属摩擦型桩。自平衡测试中，全风化泥岩侧摩阻力达到173 kPa，强风化泥岩侧摩阻力达到279 kPa，中等风化泥岩侧摩阻力达到336 kPa，实测值较规范参考值大很多。建议在桩基设计时通过室内桩和泥岩接触中型剪切摩擦试验，基于莫尔库伦理论预估泥岩侧摩阻力，为桩基承载力的确定提供参考。

Abstract:

The pile skin friction design parameters for the mudstone foundation are scant. According to the test data of large diameter deep piles of the Songhua River large bridge by means of the Osterberg cell pile test in Jilin Province, and in conjunction with the medium-scale shear test between the pile and mudstone, the interaction mechanism and load characteristics of mudstone skin friction were revealed, leading to some constructive conclusions for the design and in-depth research of the cast-in-place pile for mudstone foundation. The results show that: the end resistance of large diameter deep piles only accounts for a small part of the bearing capacity of the total load, so it belongs to the friction type pile. By means of the Osterberg cell pile test, skin friction in completely weathered mudstone, strongly weathered mudstone and moderately weathered mudstone reached 173kPa, 279kPa and 336kPa respectively. These values of mudstone skin friction are greater than specified reference ones. In the design of pile foundation, it is recommended that the mudstone skin friction estimated using the shear strength parameter measured by medium-scale shear tests, and based on the Mohr-Coulomb criterion, can provide economical and reliable parameters for estimating the bearing capacity of piles.