复合地层桥梁桩基双荷载箱自平衡法静载试验研究

Static Load Test of Double Load Box Self-balancing Method for Bridge Pile Foundation in Composite Stratum

对于分布有深厚软土层且下部为砂层的江汉平原复合地层,高速公路桥梁桩基一般为超长的大直径摩擦型桩,单桩荷载达8000~11000kN,桥梁占比高对工程项目造价影响重大,因此如何降低桥梁造价对控制工程总造价尤为重要。采用双荷载箱自平衡法静载试验,通过计算荷载箱位置、优化荷载箱安装细节、确定分级加载值及测定桩侧、桩端阻力,获取桩侧主要土层及桩端持力层的有关参数和桩基竖向变形参数,测定单桩极限承载力,一方面核验该区域复合地层桩基承载力容许值,另一方面优化荷载箱位置的布设、荷载箱安装细节及检测方法。

For the composite stratum in Jianghan Plain with deep soft soil layer distributed and sand layer at the bottom,pile foundations of expressway bridges are generally super-long large-diameter friction piles with a single pile load of 8000~11000kN.The high proportion of bridges has a great influence on the project cost.Therefore,how to reduce the bridge cost is particularly important for controlling the total project cost.The static load test of double load box self-balancing method is adopted.By calculating the position of load box,optimizing the installation details of load box,determining the tiered loading value and measuring the resistance of pile side and pile end,the relevant parameters of the main soil layer of pile side and the bearing layer of pile end and the vertical deformation parameters of pile foundation are obtained,and the ultimate bearing capacity of single pile is measured.On the one hand,the allowable bearing capacity of pile foundation in composite stratum in this area is verified.On the other hand,the layout of load box position,the installation details of load box and the detection method are optimized.