酸性土腐蚀对钢桩基础承载性能的影响
Effects of corrosion on bearing capacity of steel pile foundation in acidic soil
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摘要: 土质酸性是导致钢桩腐蚀的主要原因之一。服役于酸性土中的钢桩将会被侵蚀,导致桩身材料劣化,影响了桩基的安全性和耐久性。为了了解腐蚀桩的承载性能,通过中性和模拟酸性土两种环境下的桩基室内模型试验,测得腐蚀前后承台沉降量和桩端阻力值随桩顶加卸载的变化规律以及地面堆载固结过程中各土层沉降量、桩端阻力值、桩身轴力值以及桩侧摩阻力的变化情况。研究表明,由于腐蚀钢桩表面产生大量疏松的锈蚀产物,使桩-土界面的黏着力大大降低。桩顶承台的沉降量较未腐蚀桩大,腐蚀桩的桩端阻力值比未腐蚀桩大。而在堆载固结条件下,由于堆载作用不仅加速了桩间土体的固结,桩-土界面再次挤密,单桩以及群桩中各桩的桩端阻力值减小。腐蚀桩的中性点位置明显下移,腐蚀率越大的桩,桩侧负摩阻力的增加值越大,腐蚀前后中性点位置处桩身轴力变化率越大。研究成果可以为腐蚀条件下各类桩基载荷性能研究提供参考。Abstract: Soil acidity is one of the reasons for corrosion of steel piles. The material deterioration of steel pile foundation served in the acidic soil will affect the safety and durability of pile foundation. In order to understand the bearing capacity of corroded piles, the indoor model tests are carried out under two kinds of neutral and simulated acidic soil environments. The pile cap settlement and the pile tip resistance changing with the loading and unloading of pile top are tested. The changes of the soil layer settlement, pile tip resistance, pile axial stress and friction resistance in the process of ground load-consolidation are also measured. The results show that because the steel pile surface produces a lot of loose rust, the adhesion of pile-soil interface is greatly reduced. So the settlement of corroded pile cap is larger than that of non-corroded pile, and the end resistance of the corroded pile is also larger than that of the non-corroded pile. But under the load-consolidation conditions, because the loading accelerates the consolidation of soil between piles, the pile-soil interface is re-compacted, and the pile end resistances of both single pile and pile groups decrease. The neutral point location of corroded piles descends. The more the corrosion rate of piles, the more the lateral negative friction resistance of piles, and the more the changes of axial force at the neutral point position. The results may provide references for the studies on the loading performance of all kinds of pile foundations under corrosion condition.