天津东站地下变电站超长桩承载力试验研究

Experimental Research on Bearing Capacity of Super-Long Pile in Underground Substation of Tianjin East Railway Station

该文以天津东站地下变电站工程所使用的超长钻孔灌注桩为研究对象,采用锚固法进行超长桩的竖向抗压静荷载试验。试验结果表明:超长桩的荷载位移曲线为平缓型,属于典型的端承摩擦型桩曲线,且单桩的竖向抗压极限承载力均不小于试验最大荷载;桩身轴力的传递是自上而下进行的,即随着深度的增加轴力逐渐减小,并在荷载增加时,桩身轴力的传递性降低;桩身所承受荷载大部分由桩侧摩阻力提供,且由于地基土层性质的差异,桩侧摩阻力表现为随深度的“驼峰形”分布,当荷载达到一定值后,桩侧摩阻力不增反减,发生桩土软化的现象。

In this paper,taking the super-long bored pile used in the underground substation of Tianjin East Railway Station as the research object,the vertical compressive static load test is carried out by anchoring method.The test results show that the load-displacement curve of super-long pile is gentle,which belongs to the curve of end-bearing friction pile.Besides,the ultimate compressive bearing capacity of single pile is not less than the maximum test load;The transfer of axial force is from top to bottom,namely the axial force decreases gradually with the increase of depth,and the transfer of axial force of pile decreases with the increase of loading;Most of the loading on the pile is provided by the side friction resistance of pile.Because of the properties difference of foundation soil,the side friction resistance of pile is expressed as a“hump-shaped”distribution with depth.When the loading reaches a certain value,the side friction resistance of pile doesn't increase but decrease,and occurs the phenomenon of pile-soil softening.