混凝土灌注桩完整性及沉渣厚度的检测研究

Research on Assessing of Integrity of Concrete Bored Pile and Thickness of Sediment

研究目的:铁路基础混凝土灌注桩完整性及沉渣厚度的检测多采用反射波法进行,所测反射波曲线首先要确定桩端深度和速度值,而桩端深度和速度值的确定受多因素影响,有时造成误判,为此对铁路基础混凝土灌注桩完整性及沉渣厚度的检测进行研究。研究结论:(1)桩较短(较长)的摩擦灌注桩,桩端反射波曲线呈正向特征;桩较短的灌注端承桩以及桩较长且桩端岩层是水平状的灌注端承桩,其桩端反射波曲线呈反向特征;桩较长且桩端岩层是倾角产状以及桩体混凝土强度与桩端岩体强度相等的灌注端承桩,其桩端反射波曲线无桩底反射;(2)灌注桩混凝土坍落度应控制在容许值的上限180 mm,并取同地区、同环境、同材料、同标号混凝土坍落度上限值180 mm、下限值220 mm的模型桩反射波速度检测,得到混凝土桩的反射波速度上临界值和下临界值,且被测桩的速度值应在其上下临界值间,高于其上临界值是桩的施工桩长未达设计桩长,低于其下临界值是桩存在缺陷;(3)对于摩擦灌注桩较长的桩端反射波曲线正向幅值大于桩较短的桩端反射波曲线正向幅值,其桩较长的桩端下有软土;(4)沉渣厚度要控制在容许范围,确保混凝土灌注时在重力加速度的冲击力作用下,达到桩端下无沉渣;(5)此成果可应用于铁路基础混凝土灌注桩桩身质量完整性及沉渣厚度的检测。

Research purposes： The reflection wave method is used in assessing of integrity concrete pile and thickness of sediment,the measured reflection wave curves must first determine the pile end and the speed value,but the determine of the pile end and speed values is affected by several factors,sometimes resulting in a miscarriage of justice.Therefore the research of assessing of integrity concrete pile and thickness of sediment is necessary.Research conclusions：（ 1） For the bored friction piles,the pile end reflection wave curves showed the positive direction characteristic; For the shorter bored end bearing piles,and the longer bored end bearing pile that there is a horizontal strata under the end,the pile end reflection wave curves showed the opposite direction characteristics; For the longer bored end bearing pile that there is dip strata under pile end,and the strength of concrete pile body equal the strength of the rock under pile end,the pile end reflection wave curves showed no reflection of pile bottom characteristic.（ 2） Concrete slump of pile should be controlled in the upper limit that is 180 mm,and the same area,the same environment,the same material,the same grade concrete model pile that the upper limit of the slump is 180 mm,the lower limit is 220 mm is used to detect in reflected wave velocity,gets the upper critical value and the lower critical value of reflective concrete pile wave velocity,and the measured pile speed value should be in its critical value,higherthan the upper critical value is the construction of pile length not exceeding the design pile length,less than the lower critical value is defective piles.（ 3） The longer bored friction pile end reflection wave curves forward amplitude is larger than the short pile end reflection wave curves forward amplitude,there is the soft soil in the longer pile end.（ 4） The sediment thickness should be controlled in allowable range,to ensure no sediment under the pile end during concrete pouring when the role of impact force in the acceleration of gravity.（ 5） The results can be applied to the railway foundation concrete pile.