复合桩基地基极限承载力的下限有限元解  

Finite element lower bound limit solutions for ultimate bearing capacity of subsoil under raft of composite piled foundations

作　　者：蒋刚[1] 孙君[1,2] 王旭东[1] 

机构地区：[1]南京工业大学交通学院,江苏南京210009 [2]常州市规划设计院,江苏常州213003

出　　处：《岩土工程学报》2011年第1期128-134,共7页Chinese Journal of Geotechnical Engineering

基　　金：国家自然科学基金项目(50478005);江苏省自然科学基金项目(BK2004420);江苏省"青蓝工程"(优秀青年骨干教师资助)

摘　　要：复合桩基在达到整体极限承载状态时,因桩的"遮拦作用"使得地基极限承载力较天然地基有一定提高。其分析可简化为地基竖向极限承载力和地基土水平向绕桩作用产生的极限承载力提高值的叠加。利用下限有限元方法,求解得到地基的极限承载力和不同深度处土体绕桩阻力的数值解,并建立了绕桩阻力计算公式。绕桩阻力系数ks随桩间距的增加而逐渐减小。地基极限承载力提高值Δfu随桩间距的增加而逐渐降低。计算表明:复合桩基下绕桩阻力存在并不可忽视,承台下地基极限承载力有明确的提高,可以作为地基的安全储备。When the composite piled foundation reaches the general ultimate bearing capacity status,an increment of the ultimate bearing capacity for natural foundation is induced by ＂barrier effect＂ of piles.The analysis of the problem can be simplified for both the sum of the vertical ultimate bearing capacity of foundation and the increment of the ultimate bearing capacity of foundation soil horizontally sliding around piles.Based on the finite element plastic lower bound limit method,the numerical solutions for the vertical ultimate bearing capacity of foundation and the horizontal resistance sliding around piles varying with soil depth are obtained,and the sliding resistance formula is also established.The sliding resistance coefficient ks reduces with the increase of pile spacing.The increment of the ultimate bearing capacity Δfu decreases with the increase of pile spacing.The results indicate that the resistance sliding around piles in the composite piled foundation is being and can not be ignored,and that the ultimate bearing capacity of the composite piled foundation has certain increment,which can be regarded as the security reserve of foundation.

关 键 词：复合桩基 绕桩阻力 极限承载力提高值 下限有限元 

分 类 号：TU473[建筑科学—结构工程]