上海钻孔桩桩侧摩阻力的异化效应及分析

系统分析了上海地区钻孔桩测试资料的摩阻力实测值与规范建议值之比γ随土的状态、埋深的变化规律,并将钻孔桩摩阻力与土性参数之间存在的背离趋势分为负异化效应和正异化效应,提出异化效应是反映钻孔桩施工技术与工艺水平的度量指标。严重负异化效应出现在深埋状态好的地层表明,上海原土造浆正循环钻进施工方法在发挥深层好土的固有优势与潜力存在较严重的缺陷,并从钻孔泥浆作用和泥浆施工工艺进行了具体的分析;正异化效应出现在上海浅埋淤泥质黏性土层则说明,上海钻孔桩施工方法的某些特殊工艺具有能够充分发挥这些土层摩阻力性状的特点,并从灌注混凝土的特殊施工工艺进行了具体的分析。

Abnormal effect of skin friction of bored pile in Shanghai

Based on the tests of bored piles in Shanghai,the relationship between the ratio γ of measured values of skin friction of bored piles to suggested value recommended in foundation design codes of Shanghai was analyzed and the inconformity of skin friction of bored pile to soil properties was divided into positive and negative abnormal effect,which was taken as the appreciation index of construction technique of bored piles.It was shown by the serious negative abnormal effects emerged in deep embedded soils that there was serious defect in natural slurry of normal rotary boring construction method of Shanghai to develop the inherent and potential advantage of good soils embedded deeply,the reasons for which were analyzed according to the action and technology of boring slurry.The positive abnormal effects emerged in shallow embedded soft clay show that some special technology of construction method of bored piles in Shanghai was advantageous to develop skin friction,the reasons for which were analyzed in accordance with special technology of concreting.