沉渣对软岩嵌岩桩承载力影响的模型试验研究

Model Test of Influence of Sediment on Bearing Capacity of Pile Socketed in Soft Rock

我国华东地区普遍发育以红色碎屑岩沉积为主的泥质软岩,该地区软岩嵌岩桩在钻孔施工时极易在桩底产生一定厚度的沉渣,造成桩基极限承载力降低。结合江西泰和赣江特大桥软岩嵌岩桩工程,通过模型试验方法研究了沉渣厚度对基桩承载力的影响规律,并对《铁路桥涵地基与基础设计规范》(TB 10093—2017)中的基桩承载力计算公式进行了修正。结果表明:无沉渣基桩的荷载-沉降曲线趋于抛物线型,有沉渣基桩的承载力随沉渣厚度的增加而呈现出指数衰减的变化规律;基于模型试验结果的回归分析,提出考虑沉渣厚度的软岩嵌岩桩承载力的修正公式,可为实际工程中有沉渣基桩承载力的预测以及桩底沉渣厚度安全阈值的确定提供参考。

Muddy soft rocks dominated by red clastic rock deposits are widely developed in Eastern China.During drilling rock in the area a certain thickness of sediment is prone to be left at the bottom of bored piles,which leads to the reduction of the ultimate bearing capacity of the piles.Therefore,based on the engineering of pile socketed in soft rock of Jiangxi Taihe Ganjiang extra-large bridge,this paper applies a model test to studing the influence of sediment thickness on the bearing capacity of foundation pile,and also amends the empirical formula of the bearing capacity of foundation pile in the Code for Design on Subsoil Foundation of Railway Bridge and Culvert(TB 10093-2017).The results show that the load-displacement curves of foundation piles without sediment tend to be of parabolic type,while those of foundation piles with sediment show exponential decay with the increase of sediment thickness.Based on the regression analysis of model test results,the paper puts forward the correction formula of bearing capacity of piles socketed in soft rock,which can provide a reference for forecast of the bearing capacity of foundation piles and determination of safety threshold of sediment thickness at the bottom of the bored piles in practical construction.