竖向荷载作用下群桩的夹持作用特性
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摘要
为探明竖向荷载作用下群桩的夹持作用特性,运用数值模拟对群桩夹持作用的产生机理、作用范围等进行研究。通过对应力应变关系、压缩沉降曲线的分析,提出了夹持作用范围特征值a、b。结果表明:群桩的夹持作用的产生机理主要是群桩对桩间土"裹挟下沉"及"侧限受压"作用;在夹持作用下,群桩的桩间土可以大致分为3个特征区间,即浅层受拉区、中部传力区、底部承压区;在极限荷载下,随着桩长增加特征值a趋于一个稳定值(d=0时这个值取7),而特征值b则近似呈直线增长,且L-b保持定值12;随着桩径增大a值出现峰值,b值则保持稳定。
In order to find out the clamping characteristics of pile group under vertical loads,numerical simulation was applied to study the mechanism and scope of the clamping action.Through the analysis of the stress-strain relationship and the compression-settlement curve,the characteristic values a and b of the clamping action range were proposed.The results show that the occurrence of clamping is mainly due to the"co-sinking"and"lateral compression"effects of pile group on the inter-pile soil;under the action of clamping,the soil among the pile group can be roughly divided into three characteristic sections,namely "shallow tension zone","central force zone"and "bottom pressure zone";as the pile length increases,the characteristic value a tends to a steady value under the ultimate load(this value is taken as 7 when d=0),while the characteristic b approximates to grow linearly and L-b maintains a constant value of 12;as the diameter of pile increases,the value of aappears to reach its peak,while the value of b remains stable.
In order to find out the clamping characteristics of pile group under vertical loads,numerical simulation was applied to study the mechanism and scope of the clamping action.Through the analysis of the stress-strain relationship and the compression-settlement curve,the characteristic values a and b of the clamping action range were proposed.The results show that the occurrence of clamping is mainly due to the"co-sinking"and"lateral compression"effects of pile group on the inter-pile soil;under the action of clamping,the soil among the pile group can be roughly divided into three characteristic sections,namely "shallow tension zone","central force zone"and "bottom pressure zone";as the pile length increases,the characteristic value a tends to a steady value under the ultimate load(this value is taken as 7 when d=0),while the characteristic b approximates to grow linearly and L-b maintains a constant value of 12;as the diameter of pile increases,the value of aappears to reach its peak,while the value of b remains stable.
引文
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[2]冯忠居,谢永利,李哲,等.大直径超长钻孔灌注桩承载性状[J].交通运输工程学报,2005,5(1):24-27.
[3]冯忠居,谢永利,张宏光,等.地面水对黄土地区桥梁桩基承载力影响试验研究[J].岩石力学与工程学报,2005,27(10):1758-1765.
[4]刘金砺,邱明兵,秋仁东,等.Mindlin解均化应力分层总和法计算群桩基础沉降[J].土木工程学报,2014,47(5):118-127.
[5]何思明,卢国胜,廖祖伟.群桩沉降计算理论分析[J].岩土力学,2003,24(3):435-441.
[6]张永亮,陈兴冲,孙建飞.桥梁群桩基础非线性静力计算模型及拟静力试验研究[J].岩石力学与工程学报,2013,35(9):1799-1806.
[7]陈仁朋,梁国钱,俞济棠,等.考虑桩土相对滑移的单桩和群桩的非线性分析[J].浙江大学学报(工学版),2002,36(6):70-75.
[8]边晓亚,郑俊杰,徐志军,等.考虑长径比和容许沉降影响的群桩SLS可靠度分析[J].中南大学学报(自然科学版),2016,47(11):3839-3845.
[9]张乾青,李术才,李利平,等.考虑侧阻软化和端阻硬化的群桩沉降简化算法[J].岩石力学与工程学报,2013,35(3):615-624.
[10]汤斌,陈晓平.群桩效应有限元分析[J].岩土力学,2005,25(2):299-302.
[11]赵俭斌,王志斌,史永强.静压PHC管桩群桩效应的数值模拟分析[J].工程力学,2014,31(S1):139-144.
[12]林智勇,戴自航.由单桩载荷试验推算群桩沉降的相互作用系数法[J].岩土工程学报,2016,38(1):155-162.
[13]戴国亮,戴永兴,刘云忠,等.超长钻孔灌注桩群桩效应系数研究[J].土木工程学报,2011,44(10):107-112.
[14]谢涛,袁文忠,姚勇.超大群桩竖向承载群桩效应试验研究[J].公路交通科技,2003,(05):61-63,77.
[17]吴鹏.刚性承台超大群桩承载形状的三维有限元分析[J].铁道科学与工程学报,2007,4(2):13-18.
[18]刘金励,黄强,李华,等.竖向荷载下群桩变形性状及沉降计算[J].岩土工程学报,1995,17(6):1-13.
[19]韩云山,白晓红,贺武斌,等.垂直荷载下桩基夹持作用研究[J].岩土工程学报,2005,27(4):427-431.
[20]杜家庆,杜守继,赵丹蕾,等.竖向荷载下群桩-土-承台相互作用数值分析[J].岩土力学,2013,34(8):2414-2420.