预留土堤对桩锚支护影响的三维有限差分数值分析
|
摘要
为了城市的可持续发展,人们逐渐将开发的触手伸向了城市更高的高空以及更深的地下,在城市建筑密集区进行了大量的高层、超高层建筑和大规模的地下市政建设,这使得深基坑工程呈现出深、大、密的发展特征,并促进深基坑工程新的支护工艺的产生。桩锚支护技术诞生于1958年,并于上世纪80年代初在我国的高层建筑深基坑工程中开始得到应用,由于其广泛的地层适用条件、优于其他支护形式的技术优势以及其巨大的经济效益,被广泛应用于我国深基坑工程建设。
预留土堤,也被称作预留反压土、预留土台,是大面积基坑开挖采用中心岛法施工时所采取的一种施工手段,这是一种新兴的施工手段。当前采用预留土堤对支护结构进行临时支撑的基坑工程中,仅仅是把预留土堤看做是一种控制基坑变形和对周围环境效应的一种施工手段,而没有将其作为设计因素在支护结构设计时就进行考虑。但是预留土堤对支护结构有减小其变形和内力的作用,甚至能够取代坑内的水平支撑,达到降低工程造价、缩短工期的目的,具有良好的经济效益、社会效益和环境效益。
本文为了研究预留土堤对桩锚支护结构的影响,借助岩土工程专业的有限差分法分析软件——FLAC3D建立了桩锚支护基坑工程的三维数值模型,分别从有无预留土堤时支护桩和锚杆的反应、预留土堤宽度变化时支护桩和锚杆的反应以及高度变化时支护桩与锚杆的反应这三个方面进行分析。
通过对不同工况下的计算结果进行对比分析,得到了如下结论：预留土堤的存在能够大幅增大其作用范围内地基土竖向应力,尤其是位于靠近基坑壁附近部位的地基土；预留土堤还能够降低支护桩的水平位移；预留土堤可以有效的减小支护桩的桩身弯矩,特别是在预留土堤的作用高度内,支护桩的桩身弯矩减幅最大,且对锚杆轴力也有大幅降低的作用,最大降幅达20%；随着土堤宽度的增加,支护桩的水平位移、桩身弯矩以及锚杆轴力也会逐渐减小,但是当其宽度增加到一定值时,对桩身弯矩、桩身变形以及锚杆轴力的降低效果就减弱了,因此需要根据工程实际确定一个合理的土堤尺寸；与增加土堤宽度相比,增加土堤高度能更加显著地降低支护桩的水平位移,并且随着土堤高度的增加,支护桩的桩身弯矩、预应力锚杆的轴力也会随之减小。
In order to the sustainable development of cities,cities are gradually developing to the higher altitude and deeper undergroud,a lot of tall buildings and large-scale undergroud municipal constructions have been turnning up in central aeras of cities,so the development characteristics of deep foundation pit engineering are deep,large and close,and this also promote some new processes of deep foundation pit supporting. Pile-anchor support technology was created in1958,and in the1980s,it began to be applied to the deep foundation excavation of high-rise buildings in our country Because of its great applicability,huge technical advantage and enormous economic benefits,pile-anchor structure is widely used in the deep foundation pit construction in our county.
Earth berm,a new pit constructing means,is also called as mound.when larger foundation pit is designed to use center island method to excave the pit,there will be earth berm in the pit.Among current foundation pit with earth berm as temporary supporting,earh berm is not a design factor considered during the pit design,but an meaning to control the derformation of supporting structure and the influence to surrounding environment.But earth berm can reduce the deformation and force of supporting structure,sometimes it even can replace the horizontal support in the pit,so that earth berm cut the project cost and shorter the construction period,which has great economic benefits,social efficiency and environmental efficiency.
In order to study the effect of earth berm to pile-anchor structure,establish a3-dimention numerical model of pile-anchor supporting pit by finite difference analysis sofeware——LAC3D.In the thesis,effect of earth berm,influence change the width and height of earth berm lead to are analysed by quantification.
According to caculation results of different working conditions,get the following conclusion:earth berm can greatly increase the foundation soil vertical stress within the scope of earth berm,especially near the pit walls;earth berm can reduce the pile's displacement in the range from the height of earth berm to the bottom of pile;earth berm can effectively cut down supporting pile's moment,especially in the height of earth berm decrease amplitude is the largest,and it also can reduce cable axial force,the largest decrease amplitude can reach to20%;as the increase of earth berm's width or height,the horizontal displacement and moment of supporting pile,the cable axial force will gradually decrease,but when the width or height increase to a critical value,the decrease amplitude will be very small;compared with the increase of earth berm'width,the pile's horizontal displacement will be obviously reduced by increasing earth berm's height,and with the increase of the height,pile's moment,cable axial force will descend.
预留土堤,也被称作预留反压土、预留土台,是大面积基坑开挖采用中心岛法施工时所采取的一种施工手段,这是一种新兴的施工手段。当前采用预留土堤对支护结构进行临时支撑的基坑工程中,仅仅是把预留土堤看做是一种控制基坑变形和对周围环境效应的一种施工手段,而没有将其作为设计因素在支护结构设计时就进行考虑。但是预留土堤对支护结构有减小其变形和内力的作用,甚至能够取代坑内的水平支撑,达到降低工程造价、缩短工期的目的,具有良好的经济效益、社会效益和环境效益。
本文为了研究预留土堤对桩锚支护结构的影响,借助岩土工程专业的有限差分法分析软件——FLAC3D建立了桩锚支护基坑工程的三维数值模型,分别从有无预留土堤时支护桩和锚杆的反应、预留土堤宽度变化时支护桩和锚杆的反应以及高度变化时支护桩与锚杆的反应这三个方面进行分析。
通过对不同工况下的计算结果进行对比分析,得到了如下结论：预留土堤的存在能够大幅增大其作用范围内地基土竖向应力,尤其是位于靠近基坑壁附近部位的地基土；预留土堤还能够降低支护桩的水平位移；预留土堤可以有效的减小支护桩的桩身弯矩,特别是在预留土堤的作用高度内,支护桩的桩身弯矩减幅最大,且对锚杆轴力也有大幅降低的作用,最大降幅达20%；随着土堤宽度的增加,支护桩的水平位移、桩身弯矩以及锚杆轴力也会逐渐减小,但是当其宽度增加到一定值时,对桩身弯矩、桩身变形以及锚杆轴力的降低效果就减弱了,因此需要根据工程实际确定一个合理的土堤尺寸；与增加土堤宽度相比,增加土堤高度能更加显著地降低支护桩的水平位移,并且随着土堤高度的增加,支护桩的桩身弯矩、预应力锚杆的轴力也会随之减小。
In order to the sustainable development of cities,cities are gradually developing to the higher altitude and deeper undergroud,a lot of tall buildings and large-scale undergroud municipal constructions have been turnning up in central aeras of cities,so the development characteristics of deep foundation pit engineering are deep,large and close,and this also promote some new processes of deep foundation pit supporting. Pile-anchor support technology was created in1958,and in the1980s,it began to be applied to the deep foundation excavation of high-rise buildings in our country Because of its great applicability,huge technical advantage and enormous economic benefits,pile-anchor structure is widely used in the deep foundation pit construction in our county.
Earth berm,a new pit constructing means,is also called as mound.when larger foundation pit is designed to use center island method to excave the pit,there will be earth berm in the pit.Among current foundation pit with earth berm as temporary supporting,earh berm is not a design factor considered during the pit design,but an meaning to control the derformation of supporting structure and the influence to surrounding environment.But earth berm can reduce the deformation and force of supporting structure,sometimes it even can replace the horizontal support in the pit,so that earth berm cut the project cost and shorter the construction period,which has great economic benefits,social efficiency and environmental efficiency.
In order to study the effect of earth berm to pile-anchor structure,establish a3-dimention numerical model of pile-anchor supporting pit by finite difference analysis sofeware——LAC3D.In the thesis,effect of earth berm,influence change the width and height of earth berm lead to are analysed by quantification.
According to caculation results of different working conditions,get the following conclusion:earth berm can greatly increase the foundation soil vertical stress within the scope of earth berm,especially near the pit walls;earth berm can reduce the pile's displacement in the range from the height of earth berm to the bottom of pile;earth berm can effectively cut down supporting pile's moment,especially in the height of earth berm decrease amplitude is the largest,and it also can reduce cable axial force,the largest decrease amplitude can reach to20%;as the increase of earth berm's width or height,the horizontal displacement and moment of supporting pile,the cable axial force will gradually decrease,but when the width or height increase to a critical value,the decrease amplitude will be very small;compared with the increase of earth berm'width,the pile's horizontal displacement will be obviously reduced by increasing earth berm's height,and with the increase of the height,pile's moment,cable axial force will descend.
引文
[1]陈忠汉,黄书秩,程丽萍.深基坑工程(第二版)[M].北京：机械工业出版社,2002：14-15.
[2]陈娟.基坑桩锚支护体系现场试验与数值模拟[D].长沙：中南大学,2008：26-27.
[3]姚爱国,汤凤林.基坑支护结构设计方法讨论[J].工业建筑,2001(3)：327-332.
[4]秦四清等.深基坑工程优化设计[M].北京：地震出版社,1998：82-83.
[5]姚爱国.基坑桩锚支护设计新方法[J].探矿工程,2000(5)：33-37.
[6]姚爱国,汪国香,Simth.I.M基坑开挖与边坡支护受力分析软件包的研制.地质科技情况,1998,18(增刊)：65-72.
[7]李仁民,施占新,刘松玉等.弹性地基梁法和等值梁法进行基坑支护设计研究[J].西部探矿工程,2007(10)：17-19.
[8]杨学祥,张瑜.弹性地基梁法与经典土压力法计算支护桩内力的对比分析[J].工程建设,2010(2)：36-39.
[9]严薇,曾友谊,王维说.深基坑桩锚支护结构变形和内力分析方法探讨[J].重庆大学学报,2008(3)：344-348.
[10]JGJ 120-99建筑基坑支护技术规程[S].北京：中国建筑工业出版社,1999.
[11]Clough,G.W.,Denby,G.W..Stabilizing berm design for temporary walls in clay[J].Journal of Geotechnical Engineering Division,1977,103(GT2):75-90.
[12]Powrie,W.,Daly,W.R.Centrifuge model tests on embedded retaining walls supported by earth berms[J].Geotechnique,2002,52(2):89-106.
[13]Gourvence,Susan M.,Powrie William.Three-dimentional finite element analyses of embedded retaining walls supported by discontinuous earth berms[J].Canadian geotechnical journal,2000(1 0):1062-1077.
[14]Georgiadis M.,Anagnostopoulos C..Effect of berms on sheet-pile wall behaviour[J].Geotechnique,1998,48(4):569-574.
[15]马忠政,刘朝明.关于基坑围护结构墙内预留土堤土压力的研究探讨[J].岩土工程界,2002,5(8)：9-12.
[16]陈红庆.基坑开挖反压土作用机理及其简化分析方法研究[D].天津：天津大学,2006.
[17]李顺群,郑刚,王英红.反压土对悬臂支护结构嵌固深度的影响研究[J].岩土力学,2011,11(11)：3427-3431.
[18]陈福全,吴国荣,刘毓氚.基坑内预留土堤对基坑性状的影响分析[J].岩土工程学报,2006(增刊)：1470-1474.
[19]王选祥.预留土堤在地铁宽基坑施工中的应用探讨[J].铁道建筑,2009(2)：44-47.
[20]东南大学等合编.土力学(第二版)[M].北京：中国建筑工业出版社,2005：209-209.
[21]杨光华等.深基坑支护结构的实用计算方法及其应用[M].北京：地质出版社,2004：87-88.
[22]夏建中.土力学[M].北京：中国电力出版社,2009.
[23]尉希成.支挡结构设计手册[M].北京：中国建筑工业出版社,1995.
[24]徐杨青.深基坑工程设计的优化原理与途径[J].岩石力学与工程学报,2001,21(2)
[25]陈进.深基坑的土钉与桩锚组合式支护结构研究[D].北京：北京交通大学,2010.
[26]袁彬.深基坑支护方案优选与优化设计研究[D].合肥：安徽理工大学,2008.
[27]高伟.基坑分布开挖及支护结构变形影响因素的有限元分析[D].天津：河北工业大学,2006.
[28]余志成,施文华.深基坑支护设计与施工[M].北京：中国建筑工业出版社,1999.
[29]刘军.桩锚支护在基坑工程中的应用[J].工程价值,2011(1)：83-84.
[30]徐勇等.桩锚支护体系在大型深基坑工程中的应用[J].地下空间与工程学报,2006(04)：646-649.
[31]赵其华,彭社琴.岩土支挡与锚固工程[M].成都：四川大学出版社,2008.
[32]黄强.深基坑支护工程设计技术[M].北京：中国建材工业出版社,1995.
[33]李伟.隧道及地下工程FLAC解析方法[M].北京：中国水利水电出版社,2009.
[34]陈育民,徐鼎平FLAC/FLAC3D基础工程与实例[M].北京：中国水利水电出版社,2009.
[35]刘波,韩彦辉FLAC原理、实例与应用指南[M].北京：人民交通出版社,2005.
[36]彭文斌FLAC3D实用教程[M].北京：机械工业出版社,2007.
[37]张文生.科学计算中的偏微分方程有限差分法[M].北京：高等教育出版社,2006.
[38]Itasca.FLAC3D Fast Lagrangian Analysis of Continue in 3-Dimentions Manual Version
3.0[M]. Itasca,Minneapolis,Minuesota,2005.
[39]Itasc Consulting Group,Inc.Theory and Backgroud Version 3.0[M].
[40]Ying, Shengbin. Research of earth berm and the simplified analysis[J]. Advanced Materials Research,2010(10):1415-1420.
[41]Li, Shun-Qun, Zheng, Gang, Wang, Ying-Hong. Influence of earth berm on embedment depth of cantilever retaining structure for pit excavation[J]. antu Lixue/Rock and Soil Mechanics,2011,32(11):3427-3436.
[42]Zheng, Gang, Chen, Hong-Qing, Lei, Yang. Study of mechanism of earth berm and simplified analysis method for excavation[J]. Yantu Lixue/Rock and Soil Mechanics,2007,28(6):1161-1166.
[43]Daly, M.p., Powrie, W., Undrained analysis of earth berms as temporary supports for embedded retaining walls[J]. Proceedings of the Institution of Civil Engineers:Geotechnical Engineering,2001,149(4):237-248.
[44]J.Brian Anderson,F.C.Townsend,Calibriation of constitutive models for florida sands by drained triaxial tests.Calibration of constitutive models,2005,165 (GSP 139).
[45]Richard J.Finno,Scott B.Perkins.Observed performance of a deep excavation in clay. Journal of Geotechnical Engineering,1989,115(8).
[46]李青.基坑开挖预留土作用及其实例分析[D].广州：华南理工大学,2011.
[47]郑刚,陈红庆,雷扬等.基坑开挖反压土作用机制及其简化分析方法研究[J].岩土力学,2007,28(6)：1161-1166.
[48]包旭范,庄丽,吕培林.大型软土深基坑中心岛法施工中土台预留宽度的研究[J].岩土工程学报,2006,28(10)：1208-1212.
[49]金亚兵,周志雄.挡土墙(桩)前堆载反压或预留土体分析与计算[J].岩土力学,1999,20(3)：56-60.
[50]陈东杰,张建勋.深基坑开挖预留土堤理论研究及工程应用[J].福州工程学院学报,2004,2(1)：44-47.
[51]刘亚飞.深基坑单点桩锚支护现场试验与数值模拟研究[D].秦皇岛：燕山大学,2010.
[52]张春刚.桩锚支护深基坑检测数据分析与FLAC数值模拟[D].北京：中国地质大学(北京),2011.
[53]胡贺松.深基坑桩锚支护结构稳定性及受力变形特性研究[D].长沙：中南大学,2009.
[54]李好.深基坑桩锚支护弹塑性有限元分析[D].长沙：湖南大学,2004.
[55]魏雪.基坑开挖对坑底工程桩影响的数值模拟分析[D].济南：山东科技大学,2004.
[56]高伟.基坑分布开挖及支护结构变形影响因素的有限元分析[D].天津：河北工业大学,2006.
[2]陈娟.基坑桩锚支护体系现场试验与数值模拟[D].长沙：中南大学,2008：26-27.
[3]姚爱国,汤凤林.基坑支护结构设计方法讨论[J].工业建筑,2001(3)：327-332.
[4]秦四清等.深基坑工程优化设计[M].北京：地震出版社,1998：82-83.
[5]姚爱国.基坑桩锚支护设计新方法[J].探矿工程,2000(5)：33-37.
[6]姚爱国,汪国香,Simth.I.M基坑开挖与边坡支护受力分析软件包的研制.地质科技情况,1998,18(增刊)：65-72.
[7]李仁民,施占新,刘松玉等.弹性地基梁法和等值梁法进行基坑支护设计研究[J].西部探矿工程,2007(10)：17-19.
[8]杨学祥,张瑜.弹性地基梁法与经典土压力法计算支护桩内力的对比分析[J].工程建设,2010(2)：36-39.
[9]严薇,曾友谊,王维说.深基坑桩锚支护结构变形和内力分析方法探讨[J].重庆大学学报,2008(3)：344-348.
[10]JGJ 120-99建筑基坑支护技术规程[S].北京：中国建筑工业出版社,1999.
[11]Clough,G.W.,Denby,G.W..Stabilizing berm design for temporary walls in clay[J].Journal of Geotechnical Engineering Division,1977,103(GT2):75-90.
[12]Powrie,W.,Daly,W.R.Centrifuge model tests on embedded retaining walls supported by earth berms[J].Geotechnique,2002,52(2):89-106.
[13]Gourvence,Susan M.,Powrie William.Three-dimentional finite element analyses of embedded retaining walls supported by discontinuous earth berms[J].Canadian geotechnical journal,2000(1 0):1062-1077.
[14]Georgiadis M.,Anagnostopoulos C..Effect of berms on sheet-pile wall behaviour[J].Geotechnique,1998,48(4):569-574.
[15]马忠政,刘朝明.关于基坑围护结构墙内预留土堤土压力的研究探讨[J].岩土工程界,2002,5(8)：9-12.
[16]陈红庆.基坑开挖反压土作用机理及其简化分析方法研究[D].天津：天津大学,2006.
[17]李顺群,郑刚,王英红.反压土对悬臂支护结构嵌固深度的影响研究[J].岩土力学,2011,11(11)：3427-3431.
[18]陈福全,吴国荣,刘毓氚.基坑内预留土堤对基坑性状的影响分析[J].岩土工程学报,2006(增刊)：1470-1474.
[19]王选祥.预留土堤在地铁宽基坑施工中的应用探讨[J].铁道建筑,2009(2)：44-47.
[20]东南大学等合编.土力学(第二版)[M].北京：中国建筑工业出版社,2005：209-209.
[21]杨光华等.深基坑支护结构的实用计算方法及其应用[M].北京：地质出版社,2004：87-88.
[22]夏建中.土力学[M].北京：中国电力出版社,2009.
[23]尉希成.支挡结构设计手册[M].北京：中国建筑工业出版社,1995.
[24]徐杨青.深基坑工程设计的优化原理与途径[J].岩石力学与工程学报,2001,21(2)
[25]陈进.深基坑的土钉与桩锚组合式支护结构研究[D].北京：北京交通大学,2010.
[26]袁彬.深基坑支护方案优选与优化设计研究[D].合肥：安徽理工大学,2008.
[27]高伟.基坑分布开挖及支护结构变形影响因素的有限元分析[D].天津：河北工业大学,2006.
[28]余志成,施文华.深基坑支护设计与施工[M].北京：中国建筑工业出版社,1999.
[29]刘军.桩锚支护在基坑工程中的应用[J].工程价值,2011(1)：83-84.
[30]徐勇等.桩锚支护体系在大型深基坑工程中的应用[J].地下空间与工程学报,2006(04)：646-649.
[31]赵其华,彭社琴.岩土支挡与锚固工程[M].成都：四川大学出版社,2008.
[32]黄强.深基坑支护工程设计技术[M].北京：中国建材工业出版社,1995.
[33]李伟.隧道及地下工程FLAC解析方法[M].北京：中国水利水电出版社,2009.
[34]陈育民,徐鼎平FLAC/FLAC3D基础工程与实例[M].北京：中国水利水电出版社,2009.
[35]刘波,韩彦辉FLAC原理、实例与应用指南[M].北京：人民交通出版社,2005.
[36]彭文斌FLAC3D实用教程[M].北京：机械工业出版社,2007.
[37]张文生.科学计算中的偏微分方程有限差分法[M].北京：高等教育出版社,2006.
[38]Itasca.FLAC3D Fast Lagrangian Analysis of Continue in 3-Dimentions Manual Version
3.0[M]. Itasca,Minneapolis,Minuesota,2005.
[39]Itasc Consulting Group,Inc.Theory and Backgroud Version 3.0[M].
[40]Ying, Shengbin. Research of earth berm and the simplified analysis[J]. Advanced Materials Research,2010(10):1415-1420.
[41]Li, Shun-Qun, Zheng, Gang, Wang, Ying-Hong. Influence of earth berm on embedment depth of cantilever retaining structure for pit excavation[J]. antu Lixue/Rock and Soil Mechanics,2011,32(11):3427-3436.
[42]Zheng, Gang, Chen, Hong-Qing, Lei, Yang. Study of mechanism of earth berm and simplified analysis method for excavation[J]. Yantu Lixue/Rock and Soil Mechanics,2007,28(6):1161-1166.
[43]Daly, M.p., Powrie, W., Undrained analysis of earth berms as temporary supports for embedded retaining walls[J]. Proceedings of the Institution of Civil Engineers:Geotechnical Engineering,2001,149(4):237-248.
[44]J.Brian Anderson,F.C.Townsend,Calibriation of constitutive models for florida sands by drained triaxial tests.Calibration of constitutive models,2005,165 (GSP 139).
[45]Richard J.Finno,Scott B.Perkins.Observed performance of a deep excavation in clay. Journal of Geotechnical Engineering,1989,115(8).
[46]李青.基坑开挖预留土作用及其实例分析[D].广州：华南理工大学,2011.
[47]郑刚,陈红庆,雷扬等.基坑开挖反压土作用机制及其简化分析方法研究[J].岩土力学,2007,28(6)：1161-1166.
[48]包旭范,庄丽,吕培林.大型软土深基坑中心岛法施工中土台预留宽度的研究[J].岩土工程学报,2006,28(10)：1208-1212.
[49]金亚兵,周志雄.挡土墙(桩)前堆载反压或预留土体分析与计算[J].岩土力学,1999,20(3)：56-60.
[50]陈东杰,张建勋.深基坑开挖预留土堤理论研究及工程应用[J].福州工程学院学报,2004,2(1)：44-47.
[51]刘亚飞.深基坑单点桩锚支护现场试验与数值模拟研究[D].秦皇岛：燕山大学,2010.
[52]张春刚.桩锚支护深基坑检测数据分析与FLAC数值模拟[D].北京：中国地质大学(北京),2011.
[53]胡贺松.深基坑桩锚支护结构稳定性及受力变形特性研究[D].长沙：中南大学,2009.
[54]李好.深基坑桩锚支护弹塑性有限元分析[D].长沙：湖南大学,2004.
[55]魏雪.基坑开挖对坑底工程桩影响的数值模拟分析[D].济南：山东科技大学,2004.
[56]高伟.基坑分布开挖及支护结构变形影响因素的有限元分析[D].天津：河北工业大学,2006.