摘要
随着国民经济的快速发展,土木工程建设规模日益扩大,对地基基础提出了更高的要求,复合地基的形式也发生了较大的变化,许多新型的复合地基被应用到工程的设计和实践中去,其中刚柔性桩复合地基就是比较典型的一种新型复合地基形式。
本文在分析研究国内外复合地基分析方法及其研究现状的基础上,采用Drucker-Prager屈服准则,利用ANSYS有限元软件,对刚柔性桩复合地基进行了有限元分析,主要研究内容如下:
1.综述了复合地基的发展概况和基本理论,并回顾了刚柔性桩复合地基的研究状况。
2.利用ANSYS有限元计算分析软件,采用Drucker-Prager弹塑性理论,对刚柔性桩复合地基进行了计算机模拟。所采用的单元类型为Solid45号八节点实体单元。桩按线弹性材料计算;土体和垫层为连续的弹塑性材料。
3.研究了刚柔性桩复合地基的承载特性:探索了刚柔性桩复合地基中桩的荷载传递性状、附加应力分布情况等,并考察了刚柔性桩复合地基主要参数的变化对桩土荷载分担和复合地基沉降的影响。
4.根据对模型计算结果的分析,得到如下结论:
1)垫层厚度和模量对刚柔性桩复合地基沉降有明显影响。垫层厚度与刚柔性桩复合地基沉降呈现非线性关系;随着垫层模量的增加,刚柔性桩复合地基沉降有较为明显的降低。
2)对于刚柔性桩复合地基中的刚性长桩,长桩桩顶轴向应力随荷载的增加不断增加。同一荷载下,有垫层的长桩桩顶轴向应力远小于无垫层的长桩桩顶轴向应力,而且随荷载的增加,两者之差增大。
3)长桩变形模量的变化对刚柔性桩复合地基的影响不大。而长桩桩长的变化对刚柔性桩复合地基的影响较大。
4)刚柔性桩复合地基沉降随着柔性短桩模量的增加而减少,短桩自身分担的荷载随着短桩变形模量的增大有所增加,而桩间土和长桩分担荷载相应的减小。
5)土体的变形模量特别是刚性桩端土层的变形模量对地基沉降的影响比较明显。随着土体变形模量的增加,地基沉降减小。
6)刚性长桩置换率对刚柔性桩复合地基的沉降影响明显,复合地基的沉降随着长桩置换率的下降而增大。长桩、短桩的轴向应力随着长桩置换率的下降而增大。短桩置换率对刚柔性桩复合地基的沉降影响很小,对长桩、短桩轴向应力都有一定的影响。
Along with the fast development of national economy, the construction scale of civil engineering enlarges increasingly. The foundations have been put forward requirement by the modern construction of civil engineering. The type of composite foundation has seen changed much, and many new types have been put into design and construction. The rigid-soft-pile composite foundation is one of them.
On the basis of analyzing and studying domestic and international literatures and the situation, this paper studies the rigid-soft-pile composite foundation by using the Drucker-Prager yield criterion and ANSYS procedure.
The main contents are as follows.
1. The general developing situation and basic theory of composite foundation are summarized in this paper, and the research situation of rigid-soft-pile composite foundation is specially introduced.
2. According to Drucker-Prager elasticity-plasticity theory, the model of rigid-soft-pile composite foundation is established by using the ANSYS procedure. The element of eight-nodes Solid45 is used. The pile is a type of linear elastic material, the soil and cushion are considered as a continuous elastic-plastic material.
3. The bearing capacity and settlements character of rigid-soft-pile composite foundation are studied. The load-transfer and the distribution pattern of the additional stress of rigid-soft-pile are analyzed.
4. Based on the calculating results, the conclusions are as follow:
1) The thickness and modulus of cushion show an obvious influence on the composite foundation settlement. The composite foundation settlement reduces with the decrease thickness of cushion nonlinearly. The composite foundation settlement decreases obviously as the cushion modulus increases.
2) For the rigid long pile of rigid-soft-pile composite foundation, the axial stress of long pile top increase as the load increases. Under the same load, the axial stress of long pile top with cushion is much smaller than that without cushion, and the disparity increase as the load increases.
3) The deformation modulus of long pile has nearly no influence on the rigid-soft-pile composite foundation, while the length of long pile has great influence on the rigid-soft-pile composite foundation.
4) The settlement of rigid-soft-pile composite foundation decrease as the modulus of soft short pile increases, the loads beared by the short pile increases as the deformation modulus of short pile increase, while the loads beared by the long pile and soil among the piles decrease corresponding.
5) The deformation modulus of soil, especially of the soil under the long pile toe, has obvious influence on the composite foundation settlement. As the deformation modulus increase, the settlement decrease obviously, especially in the end of long pile.
6) The replacement ratio of long pile has obvious influence on composite foundation settlement. As the replacement ratio decrease, the settlement and the axial stresses of long pile and short pile increase. The replacement ratio of short pile has nearly no influence on composite foundation settlement, but has influence on the axial stress.
引文
[1]龚晓南,复合地基[M],浙江大学出版社,1992.
[2]龚晓南,复合地基发展概况及其在高层建筑中的应用[J],土木工程学报, 1999,32(6):3-10.
[3]龚晓南编著,复合地基理论及工程应用[M],北京,中国建筑工业出版社, 2002.11.
[4]地基处理手册编写委员会地基处理手册[M],北京,中国建筑工业出版社, 2000.8.
[5]邓超,长短桩复合地基承载力与沉降计算[D],浙江:浙江大学,2002.10.
[6] Maosong Huang, Chenrong Zhang, Zao Li. A simplified analysis method for the influence of tunneling on grouped piles[J]. Tunnelling and Underground Space Technology, 2009, 24, 410–422.
[7] Yuan-Qiang Cai, Guang-Ya Ding, Chang-Jie Xu. Amplitude reduction of elastic waves by a row of piles in poroelastic soil[J]. Computers and Geotechnics, 2009, 36 , 463–473.
[8] P.K. Emani, B.K. Maheshwari. Dynamic impedances of pile groups with embedded caps in homogeneous elastic soils using CIFECM[J]. Soil Dynamics and Earthquake Engineering, 2009, 29, 963–973.
[9] Lianyang Zhang. Nonlinear analysis of laterally loaded rigid piles in cohesionless soil[J]. Computers and Geotechnics, 2009, 36, 718–724.
[10] Emilios M. Comodromos, Mello C. Papadopoulou, Ioannis K. Rentzeperis. Pile foundation analysis and design using experimental data and 3-D numerical analysis[J]. Computers and Geotechnics, 2009, 36, 819–836.
[11]龚晓南主编,复合地基设计和施工指南[M],北京:人民交通出版社,2003.
[12]郑俊杰,袁内镇,石灰桩一粉煤灰桩在深厚软土地基中的应用[J].建筑结构,1997,(4):29-30,38.
[13]陈磊,阎明礼,组合桩复合地基在工程中的应用[J],工程勘察1999,(1) 24-26.
[14]马骥等,长短桩复合地基设计计算,岩土工程技术[J],No.2, 2001: 86-91.
[15]葛忻声,龚晓南,长短桩复合地基设计计算方法的探讨[J],建筑结构, 2002 (7):3-5.
[16]林本海,离静,桩承载性能的分析研究[J],建筑结构学报[J],2004,25(3),120-124.
[17]杨敏,杨桦,王伟,长短桩组合桩基础设计思想及其变形特性分析[J],土木工程学报,2005,38(12),103-108.
[18]倪光乐,苏克之,张志允,郭建辉,谢永锋,刚性桩复合地基理论及其在广东地区的应用[J],岩石力学与工程学报,2006,25(2),4160-4168.
[19]孙晓立,杨敏,大规模桩筏基础非线性共同作用简化分析方法[J],土木工程学报,2006, 39(9),91-97.
[20]张建辉,张素芬,邓安福,变桩径、桩长群桩桩-土体系相互作用分析模型[J],重庆建筑大学学报,2007,29(6),67-71.
[21]岳建伟,鲍鹏,组合桩的竖向承载力特性研究[J],土木工程学报,2008,41(5),59-64.
[22]李靖森,王健,杨宇,桩的抗压刚度结构[J],土木工程学报,2008,41(11),99-105.
[23]朱奎,魏纲,徐日庆,刚–柔性桩复合地基复合模量的一种解析解[J],岩石力学与工程学报,2008,27(1),3104-3109.
[24]蒋青青,孟庆玲,胡毅夫,赖伟明,沉降控制复合桩基的工程应用[J],岩石力学与工程学报,2008,27(1),3153-3158.
[25]丁继辉,袁满,王建国,多桩型组合桩复合地基承载力的可靠度分析[J],工程力学,2008,25,168-172.
[26]胡育佳,朱媛媛,程昌钧,求解几何非线性桩—土耦合系统的微分求积单元法[J],固体力学学报,2008,29(2),141-148.
[27] Jun-Jie Zheng, Sari W. Abusharar, Xian-Zhi Wang. Three-dimensional nonlinear finite element modeling of composite foundation formed by CFG–lime piles [J]. Computers and Geotechnics, 2008, 35, 637–643.
[28] Z.Y. Ai, J. Han. Boundary element analysis of axially loaded piles embedded in a multi-layered soil[J]. Computers and Geotechnics, 2009, 36, 427–434.
[29] Jack Zecher. Finite element analysis tutorial using ALGOR[M]. Schroff Development corp, 2003.
[30] John D. Reid. LS-SYNA keyword user’s manul[M]. Livermore software technology corperstion, 2003.
[31] Fluent 6.3. User’s guide[M]. Fluent Inc.; 2006.
[32] Choi BK. Advances in industrial engineering: surface modeling for CAD/CAM. Amsterdam: Elsevier Science Pubishers, 1991.
[33] Prakash V, Powell GH. DRAIN-3DX: base program user guide, version 1.10. A computer program distributed by NISEE/Computer applications, Department of CivilEngineering, University of California at Berkeley; 1993.
[34] Xinran Xiao, Mark E. Botkin, Nancy L. Johnson. Axial crush simulation of braided carbon tubes using MAT58 in LS-DYNA [J]. Thin-Walled Structures, 2009, 47, 740-749.
[35] Huu-Tai Thai, Seung-Eock Kim. Practical advanced analysis software for nonlinear inelastic analysis of space steel structures[J]. Advances in Engineering Software, 2009, 40, 786-797.
[36] A.B. Balakin, H. Dehnen, A.E. Zayats. Effective metrics in the non-minimal Einstein–Yang–Mills–Higgs theory[J]. Annals of Physics, 2008, 323, 2183-2207.
[37] Kui Jiao, Harold Sun, Xianguo Li. Numerical simulation of air flow through turbocharger compressors with dual volute design[J]. Applied Energy, 2009, 86, 2494-2506.
[38].王冒成,邵敏,有限单元法基本原理和数值方法(第二版) [M],清华大学出版社,2002.
[39] Sergio Amat, Rosa Donat, J. Carlos Trillo. On specific stability bounds for linear multiresolution schemes based on piecewise polynomial Lagrange interpolation[J]. Journal of Mathematical Analysis and Applications,2009, 358, 18-27.
[40] Aimin Xu, Zhongdi Cen. A remainder formula of numerical differentiation for the generalized Lagrange interpolation[J]. Journal of Computational and Applied Mathematics, 2009, 230, 418-423.
[41] Liping Zhu, Yinnian He. Two-level Galerkin–Lagrange multipliers method for the stationary Navier–Stokes equations[J]. Journal of Computational and Applied Mathematics, 2009, 230, 504-512.
[42] M.B. Fakhrzad, H. Khademi Zare. Combination of genetic algorithm with Lagrange multipliers for lot-size determination in multi-stage production scheduling problems[J]. 2009, 36, 10180-10187.
[43]徐芝纶,弹性力学问题的有限元法[M],河海大学教材,1996.
[44]朱伯芳,有限单元法原理与应用(第二版) [M],中国水利水电出版社,1998.
[45]龚晓南,土塑性力学,浙江大学出版社[M],1990.
[46]孙炳楠,洪涛,杨郦先,工程弹塑性力学[M],浙江大学出版社,1998.
[47]李黎明编著,ANSYS有限元分析实用教程[M],北京:清华大学出版社,2005.
[48]张胜民编著,基于有限元软件ANSYS7.0的结构分析[M],北京:清华大学出版社,2003.
[49]郭海鹰,大型通用有限元分析软件ANSYS简介及应用体会[J],无线电技术,Vo1.22,No.5,1996: 51-55.
[50]吴永红等,桩基加固软土地基的有限元分析[C],第三届全国地基处理学术讨论会论文集,1992: 538-541.
[51]刑仲星,陈晓平,复合地基力学特性研究及有限元分析[J],土工基础,Vol.14,No.2,2000: 1-4.
[52]李宁,韩煊,复合地基中褥垫层作用机理研究[J],岩土力学,Vol.21, No. l ,Mar.2000: l0-15.
[53]付景辉,宋二祥,刚性桩复合地基工作特性分析[J],岩土力学,Vo1.21, No.4,Dec.2000: 335-339.
[54]阎明礼,地基处理技术[M],中国环境科学出版社,1997.
[55]阎明礼,浅谈我国地基处理技术发展[J],岩土工程界,1999 (10) : 10-13.
[56]刘利民等,复合桩基工作性状的非线性分析[J],土木工程学报,Vo1.34,No.1,2001:56-60.
[57]张雁,黄强,半刚性桩复合地基性状分析[J],岩土工程学报,Vo1.15 , No. 2 ,1993:86-93.
