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现浇X形桩产生地基附加应力的修正Geddes应力解

ISSN号：1000-6915
期刊名称：岩石力学与工程学报
时间：2013.2.15
页码：349-362
分类：TU47[建筑科学—结构工程;建筑科学—土工工程]
作者机构：[1]河海大学岩土力学与堤坝工程教育部重点实验室,江苏南京210098, [2]浙江大学城市学院土木工程系,浙江杭州310015, [3]香港科技大学土木工程系,香港999077, [4]河海大学水资源高效利用与工程安全国家工程研究中心,江苏南京210098
相关基金：国家自然科学基金高铁联合基金项目（U1134207）; 江苏省自然科学基金项目（BK2012811）
相关项目：高速铁路软土地基沉降变形规律与控制方法研究

关键词：桩基础, 现浇X形混凝土桩, 附加应力系数, 侧摩阻力, 端阻力, GEDDES应力解, 沉降, pile foundations, X-section cast-in-place concrete pile： additional stress coefficient, shaft friction, end bearing, Geddes＇s solution, settlement

中文摘要：

现浇X形混凝土桩（X形桩）作为新型的异形截面桩,其侧摩阻力和端阻力对桩周土体产生的附加应力的计算方法尚未得到系统的研究。传统的Geddes解以圣维南原理作为模型假设的依据,忽略桩截面半径和截面形状对计算结果的影响,误差较大。在Geddes应力解的基础上,对附加应力计算过程引入二重积分,推导得出修正的Geddes应力解。通过2种计算方法对X形桩附加应力进行对比分析,结果表明：桩径越大,异形特性越突出,Geddes应力解的误差越大。用修正Geddes应力解分析X形桩侧摩阻力和端阻力产生的附加应力,可知X形桩对下卧层土体产生的附加应力是等截面面积的圆形桩的1/3左右,而端阻力产生的下卧层的附加应力是等截面面积的圆形桩的1～2倍。在1.05倍桩长以下的大部分下卧层区域内,凹弧段侧摩阻力产生的附加应力大于凸出段。随着凸出段与凹弧段侧摩阻力比值的增大,凹弧段侧摩阻产生附加应力系数逐渐减小,凸出段侧摩阻产生的附加应力系数逐渐增大,但两者之和始终小于圆形桩。对于端阻力,X形桩凹弧区产生的附加应力是凸出区的1～3倍。通过对单桩桩顶沉降对比计算,表明修正Geddes应力解与Geddes应力解相比,更适合解决X形桩地基附加应力和沉降问题。

英文摘要：

As a new cross-sectional shaped pile, the stress distribution in soil induced by the side friction（SF） and the end bearing（EB） of X-section cast-in-place concrete（XCC） pile has not been studied completely. Stress distribution in soil estimated by Geddes＇s solution has obvious difference owing to independent of the influence of pile radius and pile shapes as the bases of St. Venant＇s principle. Based on the Geddes＇s solution, the soil stress can be obtained by application of the double integration. This method can be called as modified Geddes＇s solution. The soil stress obtained by Geddes＇s solution and modified Geddes＇s solution are compared. The results indicate that the difference induced by Geddes＇s solution increases with the increasing of pile radius because of the shaped effect. Besides, soil stresses induced by the SF and EB of XCC piles with different cross-sectional dimensions are analyzed through the modified Geddes＇s solution. The results indicate that the stress in subsoil induced by XCC pile is about 1/3 times that induced by the circular pile with the same cross-sectional area; and the stress due to EB of XCC pile is 1 to 2 times that of circular pile. For large zone of subsoil （below the depth of 1.05 pile length）, the stress induced by SF on concave surface is larger than that induced by fiat surface. The stress due to SF on the fiat surface increases and that due to the concave surface decreases with the increasing of SF ratio of flat surface to concave surface. The stress induced by EB on concave zone is 1 time to 3 times that on the flat zone. The stress induced by XCC pile is always smaller than the circular pile. As the basis of the comparison analysis of the settlement of single pile, a conclusion can be drawn that the modified Geddes＇s solution is more suitable for estimating the stress distribution and settlement of XCC pile than Geddes＇s solution.

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