碎石桩单桩受荷模型试验的离散单元法数值模拟
|
摘要
为了克服连续介质模型无法有效反映碎石散体特性的缺陷,将碎石桩视为凸多边形离散块体集合,桩周软土视为理想弹塑性材料,采用二维离散单元与有限差分耦合数值方法建立了软土地基中碎石桩单桩竖向受荷模型,对碎石桩单桩受荷变形破坏及桩土相互作用全过程进行了模拟,通过荷载-沉降曲线、桩体及土体变形场应力场讨论了碎石桩单桩承载破坏机制.数值模拟结果与室内模型试验实测的荷载-沉降曲线、桩体鼓胀变形吻合良好,验证了本文数值模型的合理性.利用离散单元法建立的碎石桩模型无需复杂的本构模型假设便能较好地反映其鼓胀变形和失稳特性,同时讨论了模型的不足与有待进一步研究的问题.
A 2D DEM-FDM coupled numerical modelling scheme was proposed to simulate a single stone column in soft clay. The discrete granular materials which firm the stone column can be better simulated by the DEM model, which is beyond the capability of continuum approaches. In the proposed numerical model, the stone column was represented by discrete rigid blocks based on the Voronoi tessellation, the surrounding clay was represented by the continuum Mohr-coulomb material. The settlement,bugling deformation,failure process and the involved complicated interactions between the stone column and surrounding soil were well captured by the proposed numerical model. The accuracy of the proposed model was verified using experimental model test results. The consistency between the numerical simulation and model test results shows a good potential for the proposed modelling scheme to further study the load-deformation and failure behavior of soft soils reinforced by stone columns. The limitations of the proposed model were also discussed in this study.
A 2D DEM-FDM coupled numerical modelling scheme was proposed to simulate a single stone column in soft clay. The discrete granular materials which firm the stone column can be better simulated by the DEM model, which is beyond the capability of continuum approaches. In the proposed numerical model, the stone column was represented by discrete rigid blocks based on the Voronoi tessellation, the surrounding clay was represented by the continuum Mohr-coulomb material. The settlement,bugling deformation,failure process and the involved complicated interactions between the stone column and surrounding soil were well captured by the proposed numerical model. The accuracy of the proposed model was verified using experimental model test results. The consistency between the numerical simulation and model test results shows a good potential for the proposed modelling scheme to further study the load-deformation and failure behavior of soft soils reinforced by stone columns. The limitations of the proposed model were also discussed in this study.
引文
[1]陈建峰,韩杰.夯扩碎石桩群桩承载性状研究[J].中国公路学报,2010,23(1):26—31.CHEN J F,HAN J. Research on bearing behavior of rammed aggregate pier group[J]. China Journal of Highway and Transport,2010,23(1):26—31.(In Chinese)
[2]赵明华,张玲,邹新军,等.土工格室-碎石桩双向增强复合地基研究进展[J].中国公路学报,2009,22(1):1—10.ZHAO M H,ZHANG L,ZOU X J,et al. Research progress in twodirection reinforced composite foundation formed by geocell reinforced mattress and gravel piles[J]. China Journal of Highway and Transport,2009,22(1):1—10.(In Chinese)
[3]刘杰,张可能.散体材料桩复合地基极限承载力计算[J].岩土力学,2002,23(2):204—207.LIU J,ZHANG K N. Calculation of ultimate bearing capacity of composite foundation on discrete material pile[J]. Rock and Soil Mechanics,2002,23(2):204—207.(In Chinese)
[4]龚晓南.广义复合地基理论及工程应用[J].岩土工程学报,2007,29(1):1—13.GONG X N. Generalized composite foundation theory and engineering application[J]. Chinese Journal of Geotechnical Engineering,2007,29(1):1—13.(In Chinese)
[5]刘杰,赵明华,何杰.碎石桩复合地基承载及变形性状研究[J].湖南大学学报(自然科学版),2007,34(5):15—19.LIU J,ZHAO M H,HE J. Research on bearing and deformation characters of composite foundation with granular columns[J].Journal of Hunan University(Natural Sciences),2007,34(5):15—19.(In Chinese)
[6] BRAUNS J. Die anfangstraglast von schottersaulen im bindigen untergrund[J]. Die Bautechnik,1978,55(8):263—271.BRAUNS J. The initial load of graval pile in the clay foundation[J]. The Construction Technology,1978,55(8):263—271.(In Germany)
[7] HUGHER J,WITHERS N J. Reinforcing of soft cohesive soils with stone columns[J]. Ground Engineering,1974,7(3):42—49.
[8]陈昌富,李其泽.基于圆孔扩张理论顶部加箍碎石桩承载力计算[J].湖南大学学报(自然科学版),2011,38(10):7—12.CHEN C F,LI Q Z. Calculation of bearing capacity of geosynthetic-encased gravel pile based on cavity expansion theory[J]. Journal of Hunan University(Natural Sciences),2011,38(10):7—12.(In Chinese)
[9] WONG H Y. Field instrumentation of vibroflotation foundation[J].Field Instrumentation in Geotechnical Engineering,1974,23(4):475—487.
[10]蒋敏敏,肖昭然,蔡正银.高速公路碎石桩复合地基加固数值模拟[J].公路,2012,31(1):8—12.JIANG M M,XIAO Z R,CAI Z Y. Numerical simulation of stone columns reinforced foundation of expressway[J]. Highway,2012,31(1):8—12.(In Chinese)
[11]陈建峰,韩杰.夯扩碎石桩单桩载荷试验数值模拟[J].岩土工程学报,2009,31(9):1366—1370.CHEN J F,HAN J. Numerical modeling of loading tests on a rammed aggregate pier[J]. Chinese Journal of Geotechnical Engineering,2009,31(9):1366—1370.(In Chinese)
[12]刘洋,闫鸿翔,汪成林.复合振冲碎石桩加固机理及施工过程数值模拟[J].工程科学学报,2015,37(3):390—397.LIU Y,YAN H X,WANG C L. Reinforcement mechanism of vibrostone columns with additional wicks and numerical analysis[J].Chinese Journal of Engineering,2015,37(3):390—397.(In Chinese)
[13]蒋明镜,肖俞,陈双林,等.砂土中单桩竖向抗压承载机制的离散元分析[J].岩土力学,2010,31(S2):366—372.JIANG M J,XIAO Y,CHEN S L,et al. Discrete element analysis of bearing mechanism of single pile in sand under vertical load[J].Rock and Soil Mechanics,2010,31(S2):366—372.(In Chinese)
[14]赵明华,顾美湘,张玲,等.竖向土工加筋体对碎石桩承载变形影响的模型试验研究[J].岩土工程学报,2014,36(9):1587—1593.ZHAO M H,GU M X,ZHANG L,et al. Model tests on influence of vertical geosynthetic-encasement on performance of stone columns[J]. Chinese Journal of Geotechnical Engineering,2014,36(9):1587—1593.(In Chinese)
[15] HANY,CUNDALL P. Verification of two-dimensional LBM-DEM coupling approach and its application in modelng episodicsand production in borehole[J]. Petroleum,2016,3(2):179—189.
[16] CUNDALL P A,HART R D. Numerical modeling of discontinue[C]//Comprehensive Rock Engineering. Oxford:Pergamon Press,1993:193—213.
[17]谭鑫,HEINZ K.含层理构造的非均质片麻岩巴西劈裂试验及离散单元法数值模拟研究[J].岩石力学与工程学报,2014,33(5):938—946.TAN X,HEINZ K. Brazilian split tests and numerical simulation by discrete element method for heterogeneous gneiss with bedding structure[J]. Chinese Journal of Rock Mechanics and Engineering,2014,33(5):938—946.(In Chinese)
[2]赵明华,张玲,邹新军,等.土工格室-碎石桩双向增强复合地基研究进展[J].中国公路学报,2009,22(1):1—10.ZHAO M H,ZHANG L,ZOU X J,et al. Research progress in twodirection reinforced composite foundation formed by geocell reinforced mattress and gravel piles[J]. China Journal of Highway and Transport,2009,22(1):1—10.(In Chinese)
[3]刘杰,张可能.散体材料桩复合地基极限承载力计算[J].岩土力学,2002,23(2):204—207.LIU J,ZHANG K N. Calculation of ultimate bearing capacity of composite foundation on discrete material pile[J]. Rock and Soil Mechanics,2002,23(2):204—207.(In Chinese)
[4]龚晓南.广义复合地基理论及工程应用[J].岩土工程学报,2007,29(1):1—13.GONG X N. Generalized composite foundation theory and engineering application[J]. Chinese Journal of Geotechnical Engineering,2007,29(1):1—13.(In Chinese)
[5]刘杰,赵明华,何杰.碎石桩复合地基承载及变形性状研究[J].湖南大学学报(自然科学版),2007,34(5):15—19.LIU J,ZHAO M H,HE J. Research on bearing and deformation characters of composite foundation with granular columns[J].Journal of Hunan University(Natural Sciences),2007,34(5):15—19.(In Chinese)
[6] BRAUNS J. Die anfangstraglast von schottersaulen im bindigen untergrund[J]. Die Bautechnik,1978,55(8):263—271.BRAUNS J. The initial load of graval pile in the clay foundation[J]. The Construction Technology,1978,55(8):263—271.(In Germany)
[7] HUGHER J,WITHERS N J. Reinforcing of soft cohesive soils with stone columns[J]. Ground Engineering,1974,7(3):42—49.
[8]陈昌富,李其泽.基于圆孔扩张理论顶部加箍碎石桩承载力计算[J].湖南大学学报(自然科学版),2011,38(10):7—12.CHEN C F,LI Q Z. Calculation of bearing capacity of geosynthetic-encased gravel pile based on cavity expansion theory[J]. Journal of Hunan University(Natural Sciences),2011,38(10):7—12.(In Chinese)
[9] WONG H Y. Field instrumentation of vibroflotation foundation[J].Field Instrumentation in Geotechnical Engineering,1974,23(4):475—487.
[10]蒋敏敏,肖昭然,蔡正银.高速公路碎石桩复合地基加固数值模拟[J].公路,2012,31(1):8—12.JIANG M M,XIAO Z R,CAI Z Y. Numerical simulation of stone columns reinforced foundation of expressway[J]. Highway,2012,31(1):8—12.(In Chinese)
[11]陈建峰,韩杰.夯扩碎石桩单桩载荷试验数值模拟[J].岩土工程学报,2009,31(9):1366—1370.CHEN J F,HAN J. Numerical modeling of loading tests on a rammed aggregate pier[J]. Chinese Journal of Geotechnical Engineering,2009,31(9):1366—1370.(In Chinese)
[12]刘洋,闫鸿翔,汪成林.复合振冲碎石桩加固机理及施工过程数值模拟[J].工程科学学报,2015,37(3):390—397.LIU Y,YAN H X,WANG C L. Reinforcement mechanism of vibrostone columns with additional wicks and numerical analysis[J].Chinese Journal of Engineering,2015,37(3):390—397.(In Chinese)
[13]蒋明镜,肖俞,陈双林,等.砂土中单桩竖向抗压承载机制的离散元分析[J].岩土力学,2010,31(S2):366—372.JIANG M J,XIAO Y,CHEN S L,et al. Discrete element analysis of bearing mechanism of single pile in sand under vertical load[J].Rock and Soil Mechanics,2010,31(S2):366—372.(In Chinese)
[14]赵明华,顾美湘,张玲,等.竖向土工加筋体对碎石桩承载变形影响的模型试验研究[J].岩土工程学报,2014,36(9):1587—1593.ZHAO M H,GU M X,ZHANG L,et al. Model tests on influence of vertical geosynthetic-encasement on performance of stone columns[J]. Chinese Journal of Geotechnical Engineering,2014,36(9):1587—1593.(In Chinese)
[15] HANY,CUNDALL P. Verification of two-dimensional LBM-DEM coupling approach and its application in modelng episodicsand production in borehole[J]. Petroleum,2016,3(2):179—189.
[16] CUNDALL P A,HART R D. Numerical modeling of discontinue[C]//Comprehensive Rock Engineering. Oxford:Pergamon Press,1993:193—213.
[17]谭鑫,HEINZ K.含层理构造的非均质片麻岩巴西劈裂试验及离散单元法数值模拟研究[J].岩石力学与工程学报,2014,33(5):938—946.TAN X,HEINZ K. Brazilian split tests and numerical simulation by discrete element method for heterogeneous gneiss with bedding structure[J]. Chinese Journal of Rock Mechanics and Engineering,2014,33(5):938—946.(In Chinese)