桩体刺入全过程褥垫层的工作特性
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摘要
褥垫层是复合地基的核心构成,能协调桩、土之间的差异变形。在桩体刺入褥垫层的过程中,褥垫层的工作特性在发生变化,这方面研究还较少见。通过室内模型试验,观测桩体刺入褥垫层不同深度的桩顶压力、桩顶位移量、褥垫层的变形等试验结果,来研究褥垫层的全过程工作特性,并分析桩间土压力、桩径等对褥垫层的影响。结果表明:在桩体刺入过程中,褥垫层存在压密变形、剪切变形、压碎变形3个阶段;桩间土压力对褥垫层的整个变形过程均有影响,在其他条件相同时,褥垫层抵抗的桩顶压力、褥垫层的承载厚度均随着桩间土压力的增大而增大;桩径对褥垫层的影响主要在压碎变形阶段,褥垫层的承载厚度随桩径的增大而增大,且基本呈线性增长。
Cushion is the core of composite foundation,which can coordinate the differential deformation between piles and soils.The working characteristics of the cushion may change when the pile penetrated into the cushion,which is lack of inrestigation at present.In this paper,by means of model tests,the working characteristics of the cushion during the penetrating of pile were analyzed by measuring the pile top's pressure,displacement and deformation of cushion.Besides,the effects of the pressure between piles and soil,and the pile diameter on the cushion were analyzed.The results show that,during penetraton process,there are three different deformation stages,i.e.,compaction deformation,shear deformation and crush deformation.The pressure between piles and soils affects the whole process of the cushion's deformation,and the bearing capacity and the bearing thickness of the cushion are increased with the pressure.The effect of the pile diameter on the cushion is signigicant in the crushing deformation stage.The bearing thickness of the cushion increased linearly with the pile diameter.
Cushion is the core of composite foundation,which can coordinate the differential deformation between piles and soils.The working characteristics of the cushion may change when the pile penetrated into the cushion,which is lack of inrestigation at present.In this paper,by means of model tests,the working characteristics of the cushion during the penetrating of pile were analyzed by measuring the pile top's pressure,displacement and deformation of cushion.Besides,the effects of the pressure between piles and soil,and the pile diameter on the cushion were analyzed.The results show that,during penetraton process,there are three different deformation stages,i.e.,compaction deformation,shear deformation and crush deformation.The pressure between piles and soils affects the whole process of the cushion's deformation,and the bearing capacity and the bearing thickness of the cushion are increased with the pressure.The effect of the pile diameter on the cushion is signigicant in the crushing deformation stage.The bearing thickness of the cushion increased linearly with the pile diameter.
引文
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[2]SHEN Y P,WANG H H.Optimization design on CFGpile foundation with different cushion thickness in BeijingShanghai high-speed railway[J]. Transportation Infrastructure Geotechnology,2016,3(1):3-20.
[3]HAN X L,LI Y K,JI J,et al.Numerical simulation on the seismic absorption effect of the cushion in rigidpile composite foundation[J].Earthquake Engineering and Engineering Vibration,2016,15(2):369-378.
[4]ZHAO X L,ZHANG Q,ZHANG Q,et al.Numerical study on seismic isolation effect of gravel cushion[C]//Proceedings of the 7th International Conference on Discrete Element Methods.Dalian China,August 1-4,2016:1055-1063.
[5]SHARMA V J,VASANVALA S A,SOLANKI C H.Behaviour of cushioned composite piled raft foundation under lateral forces[J].Indian Geotechnical Journal,2015,45(1):89-97.
[6]郑刚,刘双菊,伍止超.不同厚度褥垫层刚性桩复合地基工作特性研究[J].岩土力学,2006,27(8):1357-1360.ZHENG G,LIU S J,WU Z C.Study on behavior of rigid pile composite ground with different cushion thicknesses[J].Rock and Soil Mechanics,2006,27(8):1357-1360.(in Chinese)
[7]周志军,王连坤,王敏容,等.复合地基中褥垫层的极限下限分析[J].中国科技论文,2013,8(11):1153-1158.ZHOU Z J,WANG L K,WANG M R,et al.Lower bound limit analysis of cushion in composite foundation[J].China Sciencepaper,2013,8(11):1153-1158.(in Chinese)
[8]毛前,龚晓南.桩体复合地基柔性垫层的效用研究[J].岩土力学,1998,19(2):67-73.MAO Q,GONG X N.Study on behavior of rigid pile composite ground with different cushion thicknesses[J].Rock and Soil Mechanics,1998,19(2):67-73.(in Chinese)
[9]陶景晖,卢中强,金如元,等.刚性桩复合地基桩顶埋入式垫层机理分析[J].建筑结构学报,2017,38(2):158-167.TAO J H,LU Z Q,JIN R Y,et al.Mechanism analysis of pile-top embedded cushion of rigid pile composite foundation[J]. Journal of Building Structures,2017,38(2):158-167.(in Chinese)
[10]刘杰,张可能.复合地基中垫层作用机理[J].中南工业大学学报(自然科学版),2001,32(6):568-572.LIU J,ZHANG K N.The mechanism of cushion in composite foundation[J].Journal of Central South University of Technology(Natural Science),2001,32(6):568-572.(in Chinese)
[11]亓乐,施建勇,侯仟.复合地基桩体对垫层的刺入量研究[J].岩土力学,2011,32(3):815-819,824.QI L,SHI J Y,HOU Q.Research on pile penetration into cushion of composite ground[J].Rock and Soil Mechanics,2011,32(3):815-819,824.(in Chinese)
[12]肖耀廷,党发宁.复合地基褥垫层厚度的设计方法研究[J].地下空间与工程学报,2016,12(5):1331-1335.XIAO Y T,DANG F N.Research on the design method of composite foundation cushion thickness[J].Chinese Journal of Underground Space and Engineering,2016,12(5):1331-1335.(in Chinese)
[13]郑俊杰,陈健,骆汉宾,等.刚性桩复合地基垫层破坏模式及厚度分析[J].华中科技大学学报(自然科学版),2008,36(7):120-123.ZHENG J J,CHEN J,LUO H B,et al.Analyzing failure modes and appropriate thickness of the cushion on rigid pile composite ground[J].Journal of Huazhong University of Science and Technology(Nature Science),2008,36(7):120-123.(in Chinese)
[14]朱小军,孔伟阳,费康,等.复合地基垫层刺入量模型试验与计算方法研究[J].地下空间与工程学报,2018,14(2):412-419.ZHU X J,KONG W Y,FEI K,et al.Experimental research and calculation methods of cushion penetration in composite foundation[J]. Chinese Journal of Underground Space and Engineering,2018,14(2):412-419.(in Chinese)
[15]章定文,范礼彬,刘松玉,等.水泥土搅拌桩复合地基固结机理室内模型试验[J].中国公路学报,2014,27(12):1-9.ZHANG D W,FAN L B,LIU S Y,et al.Laboratory model tests on consolidation mechanism of soft clay improved by deep mixing cement columns[J].China Journal of Highway and Transport,2014,27(12):1-9.(in Chinese)
[16]建筑地基处理技术规范:JGJ79-2012[S].北京:中国建筑工业出版社,2012.Technical code for ground treatment of buildings:JGJ79-2012[S]. Beijing:China Architecture and Building Press,2011.(in Chinese)
[17]李广信.高等土力学[M].2版.北京:清华大学出版社,2016.LI G X.Advanced soil mechanics[M].2th.Beijing:Tsinghua University Press,2016.(in Chinese)