管桩静压侧摩阻力及桩土界面滑动摩擦机制研究

Skin Friction of Jacked Pipe Pile and Mechanism Study on Sliding Friction of Pile-soil Interface

为了探究静压沉桩力学机制,开展了饱和黏性土中静压沉桩的室内模型试验,获得了静压沉桩过程中不同壁厚、桩端形式及桩径下桩侧阻力和桩身单位侧摩阻力的变化规律.同时,结合摩擦学中的黏着-犁沟理论,分析了静压沉桩过程中桩侧阻力和桩身单位侧摩阻力的的变化机制.通过室内模型试验和理论分析表明:随着贯入深度的增加,桩侧阻力逐渐增大,且桩侧阻力均随着壁厚和桩径的增加而增大,但开口桩桩侧阻力小于闭口桩;开口管桩沉桩过程中形成的土塞,对外管和内管单位侧摩阻力产生显著影响,开口桩外管单位侧摩阻力小于闭口桩,开口桩外管和内管单位侧摩阻力均随着壁厚的增加而增大;闭口桩桩径越大桩身单位侧摩阻力越大;在同一深度处,随着贯入深度的增加,桩身单位侧摩阻力不断减小,即"侧阻退化"现象.黏着-犁沟理论分析了沉桩引起的桩侧阻力和桩身单位侧摩阻力模型试验结果,揭示了饱和黏性土中静压沉桩的力学机制.

To explore the mechanisms of jacked pile,experimental model tests are conducted to investigate the variations of skin friction and unit skin friction under different wall thicknesses,pile ending forms and pile diameters in the process of jacked pile.Meanwhile the variations mechanism of skin friction and unit skin friction in the process of jacked pile are analysised based on adhesion and furrow theory in tribology.The experimental model test and theory analysis show that pile skin friction increases with the increase of penetration depth.The pile skin friction increases with the increase of wall thickness and pile diameter,but the pile skin friction of open ended pile is larger than the closed ended pile.The soil plug of open-ended pile formed in the process of jacked pile has obvious influence on unit skin friction of inner tube and external tube.The unit skin friction of external tube of open ended pile is less than the closed ended pile.The unit skin friction of inner tube and external tube of open ended pile increases with the increase of wall thickness;the larger the pile diameter of the closed ended,the larger the pile unit skin friction would be.At same depth,unit skin friction of pile decreases gradually as the depth increases,appearing“friction fatigue”,which also decreases obviously as the depth increases.The model test results of pile skin friction and pile unit skin friction caused during pile driving are analysised by the adhesion and furrow theory,which presents the mechanisms of jacked pile well.