复杂地质条件下挖孔桩完整性检测及其承载力评价

以实际工程为背景,利用反射波法检测桩身完整性,结合有限元方法,分析沉渣等缺陷对桩的变形和承载力的影响。结果表明,在复杂的地质条件下,利用反射波法可以检测桩的夹泥,搅短桩头以及桩底沉渣过厚等缺陷,但是也会出现桩端反射幅值变得微弱或几乎没有桩端反射,此时加大了确定桩端位置的难度,从而无法保证桩的承载力。利用有限元方法分析沉渣厚度对承载力的影响,结果发现沉渣厚度小于300mm时,挖孔桩单桩承载力随沉渣单位厚度变化而显著变化,而当沉渣厚度大于500mm后,沉渣单位厚度大小的变化对单桩承载力变化的影响不很明显。

Integrity Testing and Bearing Capacity Evaluation of Digging Pile under Complex Geological Conditions

The integrity of pile is investigated by reflected wave method,and combined with finite element analysis approach,the influence of defects,such as sediment,on the deformation and bearing capacity of pile is analyzed in accordance with practical projects.As an interpretation of the results,one can infer that the reflected wave method is capable of detecting the defects such as infiltrated mud,diameter-shrinkage,and excessive sediment in the bottom of pile under complex geological conditions.However,the amplitude of reflected wave in the bottom of pile may become weak or even negligible,which would result in the difficulty to determine the location of pile end,as a consequence,the bearing capacity of pile cannot be guaranteed.The finite element method is employed to analyze the effect of the sediment thickness on the bearing capacity of pile.It can be concluded that the single pile bearing capacity would change dramatically with the variation of the sediment thickness when the sediment thickness is within the limit of 300 mm.On the other hand,the sediment thickness changes would exert almost negligible effect on the single pile bearing capacity under the circumstances of larger sediment thickness beyond 500 mm.