黄土塬地区大直径长桩承载性状与优化设计研究

doi:10.13722/j.cnki.jrme.2015.1675

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摘要黄土塬地区桩基问题研究匮乏，依托陇东首栋超高层建筑，在试验桩身上布置混凝土应变计、钢筋应力计，承台底板下和桩端布置土压力盒，对原地基土、单桩基础和单桩承台基础分别进行现场原位载荷试验；利用ANSYS有限元软件对全短桩基、全长桩基及长短桩组合桩基在竖向荷载作用下的筏板沉降变形、地基土应力场与沉降变化进行分析。结果发现：(1) 黄土塬场地地基土夹层交互分布、湿陷性不连续，存在由非湿陷性黄土变成湿陷性黄土的可能，桩周土层对桩基内力传递与分布影响显著，桩身出现多个中性点，湿陷性土层下限深度确定更加复杂；(2) 各级荷载作用下，桩基Q-S曲线呈缓变型发展，表现为典型的摩擦型桩，桩身内力发挥具有异步性；试验加载至8 000 kN时，桩顶最大沉降为8.15 mm，单桩和单桩承台端阻力分别仅占桩顶荷载的4.8%和2.1%；(3) 单桩承台基础中承台底部实测反力呈倒“盆”形分布、边缘应力较大，桩–土–承台体系的承载性能优于单桩基础；桩基础设计时，可结合经验以承载力和最大允许变形量进行控制，提高桩身线刚度抵抗自身压缩变形，减小桩基上部沉降；(4) 长短桩组合桩基础充分利用与发挥了长桩控制沉降的作用与地基土浅层承载的能力，减少了长桩数量，节省了桩基造价，值得进一步深入研究。

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	朱彦鹏1
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	杨校辉1
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	马天忠1
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	李安民1
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关键词 ：桩基础, 黄土塬地基, 大直径长桩, 载荷试验, 数值模拟, 长短桩组合桩基础

Abstract：The research of pile foundation in loess subsoil is insufficient. The first super high-rise building in Longdong was investigated with the concrete strain meters and stress gauges installed on the pile body，and the soil pressure cells placed under the pile cap and pile tip. The software ANSYS was used to analyze the raft settlement of the whole short pile，the whole long pile and the composite pile foundation with long and short piles and to analyze the stress field and settlement variation of soil foundation. The ground soil has the collapsible and non-collapsible loess layers. The non-collapsible loess may become collapsible. The soil layers around the pile has the major effect on the transmission and distribution of the internal pile force. There are several neutral points on the pile body，so the determination of the lower limit of collapsible soil is more complicated. Under the different load levels，the Q-S curves of the piles vary slowly, indicating that the piles are frictional ones. The internal force of pile body develops asynchronously. When the test load reaches up to 8 000 kN，the maximum settlement on the pile top is 8.15 mm and the resistance of the single pile and single pile cap is 4.8% and 2.1% of load on pile top respectively. The measured reaction force at cushion cap of the single pile shapes like an inverted basin and the edge stress is relatively greater. The load carrying properties of pile-soil-cushion cap system are better than the one of single pile foundation. The composite pile foundation with long and short piles makes the full use of the settlement control ability of long pile and the shallow bearing ability of foundation soil to reduce the number of long piles which reduces the cost of pile foundation.

Key words： pile foundation loess subsoil large-diameter long pile load test numerical simulation composite pile foundation with long and short piles

引用本文:

朱彦鹏1，2，杨校辉1，2，马天忠1，2，李安民1，2. 黄土塬地区大直径长桩承载性状与优化设计研究[J]. 岩石力学与工程学报, 2017, 36(4): 1012-1023.
ZHU Yanpeng1，2，YANG Xiaohui1，2，MA Tianzhong1，2，LI Anmin1，2. Bearing behavior and optimization design of large-diameter long pile #br# foundation in loess subsoil#br#. , 2017, 36(4): 1012-1023.

链接本文:

http://www.rockmech.org/CN/10.13722/j.cnki.jrme.2015.1675 或 http://www.rockmech.org/CN/Y2017/V36/I4/1012

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