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山东省东明黄河公路大桥单桩竖向静载试验采用拉压锚法加载装置实现了45000kN超大吨位加载,为研究黄河中下游地区大直径超长灌注桩承载特性及荷载传递机理提供了有价值的参考数据。试验结果表明:两根试桩桩顶Q-s曲线均呈缓变型,表现出摩擦桩性状;桩顶在低竖向荷载作用下,桩身弹性压缩量占超长桩桩顶沉降量的绝大部分,该比重随桩顶竖向荷载的增加而减小;试桩加载至45000kN时,桩身弹性压缩量占桩顶沉降量的比例仍超过50%;由于桩侧土层侧摩阻力发挥的异步性,超长桩上部土层的侧摩阻力先于下部土层发挥;侧摩阻力发挥过程中,超长桩中部土层侧摩阻力软化效应严重,而深部土层侧摩阻力具有明显的增强效应,超长桩设计计算时应考虑不同深度土层侧摩阻力的软化效应或增强效应。
The vertical static load test of single pile of Dongming Yellow River Highway Bridge in Shandong Province adopts the tension-compression anchor loading device to realize the large-tonnage load of 45000kN, which provides valuable information for studying the bearing characteristics and load transmission mechanism of large-diameter overlength casting piles in the middle and lower reaches of the Yellow River. Reference data The test results show that the top Qs curves of two test piles show a slowly changing shape and show the characteristics of friction piles. Under low vertical loads, the elastic compression of the piles accounts for the vast majority of the settlement of overlength piles , And the proportion decreases with the increase of pile top vertical load. When the test pile is loaded to 45000kN, the proportion of the elastic compression of pile body to the settlement of pile top still exceeds 50%. Because of the asynchronous The lateral friction of the soil layer above the long pile is earlier than that of the lower soil layer. During the development of the side friction, the side skin frictional resistance of the middle layer of the long pile is serious, while the side frictional resistance of the deep soil layer is obviously enhanced Effect, the softening effect or strengthening effect of soil friction at different depths should be considered in the design of super-long pile.