基于薄层单元法的单桩挤土效应数值模拟

doi:10.3969/j.issn.1007-2861.2013.02.019

摘要/Abstract

摘要： 通常预制桩施工会产生挤土效应, 这会对周围环境产生不利影响. 根据某桩基工程施工的实际情况, 利用大型有限元分析软件Abaqus, 通过在桩土间增加薄层单元的方法对单桩施工的挤土效应进行了数值模拟. 薄层单元的厚度取0.08 m, 其力学性质参数介于桩和土之间. 模拟时, 薄层单元近土侧与土中节点进行位移耦合, 而近桩侧则采用摩尔-库伦(Mohr-Coulomb)定律来反映桩体和单元之间的接触关系. 通过数值模拟, 探讨了外部荷载作用下抗压桩的变化特点, 得到了桩顶的荷载与桩入土深度的关系曲线, 分析了打入桩施工的有效影响距离和有效影响深度, 对比研究了有限元数值模拟结果与圆孔扩张理论的解析计算结果. 数值模拟结果表明, 单桩施工的水平向有效影响范围大约为5 倍桩径, 竖直向约为2 倍桩长. 数值模拟结果和解析计算结果比较接近. 使用薄层单元法进行打桩挤土效应数值模拟, 符合桩基工程施工的实际情况, 反映了桩土接触面的变形机理与受力状态. 这对桩基工程设计和施工具有一定的参考价值.

关键词: 数值模拟, 薄层单元, 挤土效应, 桩基础

Abstract: Compaction effect usually occurs in the construction of precast piles. This effect may have a negative impact on the environment. A pile-soil model is simulated based on a numerical method using the finite element software Abaqus. A specially-defined contact element of pile-soil interface is used with a thickness of 0.08 m to simulate the mechanical features of the interface between the pile and soil. The mechanical parameters of the elements are set between those of the pile and soil, and the elements close to the soil are coupled with the element nodes in the soil. The Mohr-Coulomb’s law is applied to reflect the constitutive law of the elements close to the pile. Based on the numerical simulation, the effective distance and depth resulting from pile driving
are analyzed. The characteristic change of the compressive pile is explored. The relationship between the load and the penetration depth together with the side resistance distribution of the pile are then obtained. The results of simulation and cavity expansion theory are compared. It shows that the effective horizontal and vertical distances are about 5 and 2 times the diameter of the pile, respectively. The described method may provide references to the construction and design in the pile engineering.

Key words: thin-layered element, compaction effect, numerical simulation, pile foundation

中图分类号:

TU 473.1

赵健利, 冯旭. 基于薄层单元法的单桩挤土效应数值模拟[J]. 上海大学学报(自然科学版), 2013, 19(2): 208-214.

ZHAO Jian-li, FENG Xu. Numerical Simulation of Compaction Effects of Single Driven Pile Using Thin-Layered Element Technique[J]. Journal of Shanghai University（Natural Science Edition）, 2013, 19(2): 208-214.

参考文献

[1] 徐建平, 周健, 徐朝阳. 群桩挤土效应的数值模拟[J]. 同济大学学报: 自然科学版, 2000, 28(6): 721-725.

[2] Goodman R E, Taylor R L, Brekke T L. A model for the mechanics of jointed rocked [J]. Journal of the Soil Mechanics and Foundations Division, 1968, 94(4): 637-660.

[3] Desai C S, Zaman M M. Thin layer element for interfaces and joints [J]. International Journal for Numerical and Analytical Methods in Geomechanics, 1984, 8(1): 19-43.

[4] Clough G W, Duncan J M. Finite element analysis of retaining wall behavior [J]. Journal of the Soil Mechanics and Foundations Division, 1971, 97(12): 1657-1673.

[5] 殷宗泽, 朱泓, 许国华. 土与结构材料的接触面的变形及数学模型[J]. 岩土工程学报, 1994, 16(3): 14-22.

[6] 张冬霁, 卢廷浩. 一种土与结构接触面模型的建立及应用[J]. 岩土工程学报, 1998, 20(6): 62-66.

[7] 栾茂田, 武亚军. 土与结构接触面的非线性弹性-理想塑性模型及应用[J]. 岩土力学, 2004, 25(4): 507-513.

[8] Mabsout M, Sadek S. A study of the effect of driving on pre-bored piles [J]. International Journal for Numerical and Analytical Methods in Geomechanics, 2003, 27(2): 133-146.

[9] Kucukarslan S, Banerjee P K. Inelastic analysis of pile-soil interaction [J]．Journal of Geotechnical and Geoenvironmental Engineering, 2004, 130(11): 1152-1157．

[10] 陈仁鹏, 周万欢, 曹伟平, 等. 改进的桩土界面荷载传递双曲线模型及在单桩负摩阻力时间效应研究中的应用[J]. 岩土工程学报, 2007, 29(6): 824-830.

[11] 李镜培, 李雨浓, 张述涛. 成层地基中静压单桩挤土效应试验[J]. 同济大学学报: 自然科学版, 2011, 39(6): 824-829.

[12] 雷华阳, 李肖, 陆培毅, 等. 管桩挤土效应的现场试验和数值模拟[J]. 岩土力学, 2012, 33(4): 1006-1012.

[13] 陈开旭, 安关峰, 鲁亮. 采用有厚度接触面单元对桩基沉降的研究[J]. 岩土力学, 2000, 21(1): 92-95.

[14] 陈念军, 李方柱. 土的变形模量和压缩模量[J]. 武汉大学学报: 工学版, 2010, 48(8): 262-265.

[15] 鹿群, 龚晓南, 崔武文, 等. 静压单桩挤土位移的有限元分析[J]. 岩土力学, 2007, 28(11): 2427-2430.
[16] 中华人民共和国建设部. GB 50021—2001岩土工程勘察规范[S]. 北京: 中国建筑工业出版社, 2009.

[17] 张孟喜. 土力学原理[M]. 武汉: 华中科技大学出版社,2007.