混凝土开口管桩竖向承载力的经验参数法设计模型  

A design framework for evaluating the vertical bearing capacity of open-ended concrete pipe pile from empirical correlations

作　　者：俞峰[1,2] 张忠苗[2] 

机构地区：[1]浙江理工大学,浙江杭州310018 [2]浙江大学岩土工程研究所,浙江杭州310058

出　　处：《土木工程学报》2011年第7期100-110,共11页China Civil Engineering Journal

基　　金：浙江省自然科学基金(Y1090610)

摘　　要：混凝土开口管桩的竖向承载性状因为土塞涌入而与闭口管桩存在区别,在利用预制桩单位极限侧阻和端阻建议值预测单桩竖向承载力时,应根据混凝土开口管桩的特点加以修正。沉桩后的土塞率指标综合反映了土质、桩尺寸和沉桩方式等因素的影响。利用该指标并结合实测数据分析,可以围绕土塞效应使用半解析半经验方法计算桩端承载力,可以描述开口管桩与一般预制桩的挤土效应差异并进行桩侧承载力修正,还可以在一定程度上体现静压桩与打入桩的承载力差异。分析显示,桩基规范和勘察报告一般倾向于提出偏保守的单位极限侧阻和端阻建议值,因此按经验参数法设计模型计算的单桩极限承载力有可能小于实测值。设计模型的优化依赖于更多开口和闭口管桩试验的对比研究。The axial performance of open-ended concrete pipe-pile differs from the close-ended construction,primarily due to the presence of soil plug.Application of the recommended unit shaft and base capacities for close-ended pile to the open-ended type is feasible by putting particular concern on the pile end condition.As the plug length ratio accounts for the influences of ground condition,pile geometry and installation method,this study intends to correlate the capacity of open-ended pile with this integrated index by establishing a set of empirical relations.A semi-empirical procedure is involved to assess the base capacity,including the soil-plugging behavior,while a reduction in shaft capacity is taken into account with regard to the degree of soil-squeezing.The plug length ratio is also shown to be an explicit indicator of the discrepancy in capacities of identical jacked and driven piles.Current pile design practices and geotechnical investigations in China tend to give relatively conservative recommendations for the unit shaft and base capacities.As a result,empirical correlations based on these suggested values are likely to underpredict the pile capacity.The design framework is yet open for further improvement provided that more parametric test studies on open-and close-ended piles have been performed.

关 键 词：混凝土管桩 土塞率 挤土效应 单桩承载力 

分 类 号：TU473.11[建筑科学—结构工程] TU473.12[建筑科学—土工工程]