铁路路基下膨胀土长短微型桩抗隆起研究
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摘要
在非饱和膨胀土地区,地基隆起变形严重威胁着高速无砟铁路安全运营。为减弱或消除地基隆起变形,降低高速铁路工程投资,结合非饱和膨胀土地基气候影响深度特征,将传统微型桩改进为一种抗隆起的长短微型桩结构。再由若干基本假定、工作机制及应力路径分析,推导长短微型桩加固膨胀土地基后隆起量的计算方法。依托云桂铁路路基基床现场湿干试验,开展实际工程案例及设计关键参数研究,结果表明,相比天然地基,长短微型桩可有效减弱地基隆起量,减幅约60%;增大长短微型桩桩径、缩小桩间距、优化线路标高及适当增加桩长均可减弱甚至消除地基隆起变形。基于参数敏感性、影响权重比及布桩方案分析,提出膨胀土区域无砟轨道路基基底长短微型桩的抗隆起设计原则,即推荐采用"小桩径、小桩间距"长短微型桩加固无砟轨道路基基底膨胀土,长微型桩桩长宜略大于临界桩长且不应小于大气影响深度,短微型桩桩长不宜小于大气急剧影响层深度。
In unsaturated expansive soil regions,ground upheaval threats the safe operation of high-speed ballastless railway. To reduce or eliminate the ground upheaval and to cut down the engineering investment of high-speed railway,a long-short micropile structure considering atmospheric influence depth of unsaturated expansive soil foundations was proposed on the basis of the traditional micropiles. In accordance with several basic assumptions,an upheaval calculation methodology of expansive soil foundations reinforced by long-short micropiles was derived based on the analysis of working mechanics and stress path. Field tests of swelling-shrinkage responses of an expansive soil foundation under the subgrade bed of Yun-Gui high-speed railway were performed,and key design parameters were investigated. The results show that long-short micropiles can significantly reduce the upheaval of expansive soil foundations by about 60%. The ground upheaval can be reduced or even eliminated by increasing the pile diameter of long-short micropiles,reducing the pile spacing,optimizing the elevation of the railway line or appropriately increasing the pile length. Based on analysis of parameter sensitivity,influence weight ratio and pile setting scheme,a design principle of long-short micropiles to control ground upheaval under ballastless track subgrades in expansive soil regions was proposed,namely that small pile diameter and small pile spacing is recommended to reinforce expansive soils under ballastless track subgrade,that the length of long micropiles should be slightly larger than the critical pile length and not less than the atmospheric influence depth,and that the length of short micropiles should be greater than the depth of soil layer affected by atmosphere dramatically.
In unsaturated expansive soil regions,ground upheaval threats the safe operation of high-speed ballastless railway. To reduce or eliminate the ground upheaval and to cut down the engineering investment of high-speed railway,a long-short micropile structure considering atmospheric influence depth of unsaturated expansive soil foundations was proposed on the basis of the traditional micropiles. In accordance with several basic assumptions,an upheaval calculation methodology of expansive soil foundations reinforced by long-short micropiles was derived based on the analysis of working mechanics and stress path. Field tests of swelling-shrinkage responses of an expansive soil foundation under the subgrade bed of Yun-Gui high-speed railway were performed,and key design parameters were investigated. The results show that long-short micropiles can significantly reduce the upheaval of expansive soil foundations by about 60%. The ground upheaval can be reduced or even eliminated by increasing the pile diameter of long-short micropiles,reducing the pile spacing,optimizing the elevation of the railway line or appropriately increasing the pile length. Based on analysis of parameter sensitivity,influence weight ratio and pile setting scheme,a design principle of long-short micropiles to control ground upheaval under ballastless track subgrades in expansive soil regions was proposed,namely that small pile diameter and small pile spacing is recommended to reinforce expansive soils under ballastless track subgrade,that the length of long micropiles should be slightly larger than the critical pile length and not less than the atmospheric influence depth,and that the length of short micropiles should be greater than the depth of soil layer affected by atmosphere dramatically.
引文
[1]GEORGE X,PANAGIOTIS K,ANANIAS T.Road construction on swelling soils:the case of Strymi soils,Rhodope,Thrace,Northern Greece[J].Bulletin of Engineering Geology and the Environment,2004,63:93-101.
[2]FREDLUND D G,RAHARDJO H.Unsaturated soils mechanics in engineering practice[M].New York:Wiley,2012:403-408.
[3]中华人民共和国行业标准编写组.TB 10621-2014高速铁路设计规范[S].北京:中国铁道出版社,2014.(The Professional Standards Compilation Group of the People's Republic of China.TB10621-2014 Code for design of high speed railway[S].Beijing:China Railway Press,2014.(in Chinese))
[4]马丽娜,严松宏,王起才,等.客运专线无碴轨道泥岩地基原位浸水膨胀变形试验[J].岩石力学与工程学报,2015,34(8):1 684-1 691.(MA Lina,YAN Songhong,WANG Qicai,et al.In-situ tests on swelling deformation of mudstone foundation upon soaking under ballastless truck of passenger railway line[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(8):1 684-1 691.(in Chinese))
[5]肖小文,王立川,阳军生,等.高地应力区缓倾互层岩体无砟轨道隧道底部隆起的成因分析及整治方案[J].中国铁道科学,2016,37(1):78-84.(XIAO Xiaowen,WANG Lichuan,YANG Junsheng,et al.Cause analysis and treatment scheme for bottom heave of ballsastless track tunnel in nearly horizontally interbedded rock mass with high geostress[J].China Railway Science,2016,37(1):78-84.(in Chinese))
[6]中华人民共和国国家标准编写组.GB 50112-2013膨胀土地区建筑技术规范[S].北京:中国建筑工业出版社,2012.(The National Standards Compilation Group of the People's Republic of China.GB50112-2013 Technical code for buildings in expansive soil regions[S].Beijing:China Architecture and Building Press,2012.(in Chinese))
[7]ELLISON R D,D'APPOLONIA E,THIERS G R.Load deformation mechanism for bored piles[J].Journal of the Soil Mechanics and Foundations Division,1971,97:661-678.
[8]SOROCHAN E A.Use of piles in expansive soils[J].Soil Mechanics and Foundation Engineering,1974,11(1):33-38.
[9]范臻辉.膨胀土地基胀缩特性及桩-土相互作用研究[博士学位论文][D].长沙:中南大学,2007.(FAN Zhenhui.Research on swelling-shrinking characteristic and pile-soil interaction of expansive soil foundation[Ph.D.Thesis][D].Changsha:Central South University,2007.(in Chinese))
[10]吴志伟,宋汉周,王宏宇,等.膨胀土中基桩胀拔力原型试验研究[J].岩土力学,2012,33(增2):173-177.(WU Zhiwei,SONGHanzhou,WANG Hongyu,et al.Prototype experimental study of expansive force of pile embedded in expansive soil[J].Rock and Soil Mechanics,2012,33(Supp.2):173-177.(in Chinese))
[11]BRUCE D A,DIMILLIO A F,JURAN I.Introduction to micropiles:an international perspective[C]//Foundation Upgrading and Repair for Infrastructure Improvement.[S.l.]:[s.n.],1995:2 081-2 088.
[12]TURNER J P,KULHAWY F H.Drained uplift capacity of drilled shafts under repeated axial loading[J].Journal of Geotechnical Engineering,1990,116(3):470-491.
[13]LUTENEGGER A J,MILLER G A.Uplift capacity of small-diameter drilled shafts from In situ tests[J].Journal of Geotechnical Engineering,1994,120(8):1 362-1 380.
[14]吕凡任,陈仁朋,陈云敏,等.软土地基上微型桩抗压和抗拔特性试验研究[J].土木工程学报,2005,38(3):99-105.(LU Fanren,CHEN Renpeng,CHEN Yunmin,et al.Field tests on compression and uplift behavior of micropiles in soft ground[J].China Civil Engineering Journal,2005,38(3):99-105.(in Chinese))
[15]黄广龙,方乾,苏荣臻.软土地基微型桩抗拔试验研究[J].岩土工程学报,2010,32(11):1 788-1 793.(HUANG Guanglong,FANGQian,SU Rongzhen.Field test on uplift behavior of micropiles in soft ground[J].Chinese Journal of Geotechnical Engineering,2010,32(11):1 788-1 793.(in Chinese))
[16]徐再楼.灌注细石混凝土微型桩在软土地基上的抗拔性试验研究[J].公路工程,2016,41(5):222-225.(XU Zailou.Experimental study on uplift resistance of micropiles in soft soil foundation[J].Highway Engineering,2016,41(5):222-225.(in Chinese))
[17]陈伟志,蒋关鲁,袁泽华,等.低矮路堤下膨胀土地基现场浸水试验研究[J].岩石力学与工程学报,2014,33(8):1 609-1 618.(CHENWeizhi,JIANG Guanlu,YUAN Zehua,et al.Field soaking tests on expansive soil foundation under low embankment[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(8):1 609-1 618.(in Chinese))
[18]陈伟志.低矮路堤荷载下膨胀土地基胀缩变形特性研究[博士学位论文][D].成都:西南交通大学,2015.(CHEN Weizhi.Study on characteristics of swelling-shrinking deformation of expansive soil foundation under low embankment loading[Ph.D.Thesis][D].Chengdu:Southwest Jiaotong University,2015.(in Chinese))
[19]蒋关鲁,王海龙,李安洪.高速铁路路基基底应力计算方法研究[J].铁道建筑,2009,(4):65-69.(JIANG Guanlu,WANG Hailong,LI Anhong.Study on the base stresses calculation methods of high-speed railway subgrade[J].Railway Engineering,2009,(4):65-69.(in Chinese))
[20]蒋关鲁,王海龙,李安洪,等.土质路基荷载下地基反力试验研究[J].铁道学报,2012,34(6):69-74.(JIANG Guanlu,WANG Hailong,LI Anhong,et al.Experimental study on ground reaction under subgrade[J].Journal of the China Railway Society,2012,34(6):69-74.(in Chinese))
[21]蒋关鲁,王力伟,杭红星.路桥交界处地基附加应力修正计算方法[J].岩土工程学报,2013,35(2):208-218.(JIANG Guanlu,WANG Liwei,HANG Hongxing.The modified additional stress calculation method of bridge approach foundation under the subgrade load[J].Chinese Journal of Geotechnical Engineering,2013,35(2):208-218.(in Chinese))
[22]陈伟志,蒋关鲁,王智猛,等.分级连续加载条件下原状膨胀土固结变形研究[J].岩土力学,2014,35(3):710-716.(CHEN Weizhi,JIANG Guanlu,WANG Zhimeng,et al.Study of consolidation deformation of undisturbed expansive soil under stage continuous loading conditions[J].Rock and Soil Mechanics,2014,35(3):710-716.(in Chinese))
[23]郑健龙,张锐.公路膨胀土路基变形预测与控制方法[J].中国公路学报,2015,28(3):1-10.(ZHENG Jianlong,ZHANG Rui.Prediction and control method for deformation of highway expensive soil subgrade[J].China Journal of Highway and Transport,2015,28(3):1-10.(in Chinese))
[2]FREDLUND D G,RAHARDJO H.Unsaturated soils mechanics in engineering practice[M].New York:Wiley,2012:403-408.
[3]中华人民共和国行业标准编写组.TB 10621-2014高速铁路设计规范[S].北京:中国铁道出版社,2014.(The Professional Standards Compilation Group of the People's Republic of China.TB10621-2014 Code for design of high speed railway[S].Beijing:China Railway Press,2014.(in Chinese))
[4]马丽娜,严松宏,王起才,等.客运专线无碴轨道泥岩地基原位浸水膨胀变形试验[J].岩石力学与工程学报,2015,34(8):1 684-1 691.(MA Lina,YAN Songhong,WANG Qicai,et al.In-situ tests on swelling deformation of mudstone foundation upon soaking under ballastless truck of passenger railway line[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(8):1 684-1 691.(in Chinese))
[5]肖小文,王立川,阳军生,等.高地应力区缓倾互层岩体无砟轨道隧道底部隆起的成因分析及整治方案[J].中国铁道科学,2016,37(1):78-84.(XIAO Xiaowen,WANG Lichuan,YANG Junsheng,et al.Cause analysis and treatment scheme for bottom heave of ballsastless track tunnel in nearly horizontally interbedded rock mass with high geostress[J].China Railway Science,2016,37(1):78-84.(in Chinese))
[6]中华人民共和国国家标准编写组.GB 50112-2013膨胀土地区建筑技术规范[S].北京:中国建筑工业出版社,2012.(The National Standards Compilation Group of the People's Republic of China.GB50112-2013 Technical code for buildings in expansive soil regions[S].Beijing:China Architecture and Building Press,2012.(in Chinese))
[7]ELLISON R D,D'APPOLONIA E,THIERS G R.Load deformation mechanism for bored piles[J].Journal of the Soil Mechanics and Foundations Division,1971,97:661-678.
[8]SOROCHAN E A.Use of piles in expansive soils[J].Soil Mechanics and Foundation Engineering,1974,11(1):33-38.
[9]范臻辉.膨胀土地基胀缩特性及桩-土相互作用研究[博士学位论文][D].长沙:中南大学,2007.(FAN Zhenhui.Research on swelling-shrinking characteristic and pile-soil interaction of expansive soil foundation[Ph.D.Thesis][D].Changsha:Central South University,2007.(in Chinese))
[10]吴志伟,宋汉周,王宏宇,等.膨胀土中基桩胀拔力原型试验研究[J].岩土力学,2012,33(增2):173-177.(WU Zhiwei,SONGHanzhou,WANG Hongyu,et al.Prototype experimental study of expansive force of pile embedded in expansive soil[J].Rock and Soil Mechanics,2012,33(Supp.2):173-177.(in Chinese))
[11]BRUCE D A,DIMILLIO A F,JURAN I.Introduction to micropiles:an international perspective[C]//Foundation Upgrading and Repair for Infrastructure Improvement.[S.l.]:[s.n.],1995:2 081-2 088.
[12]TURNER J P,KULHAWY F H.Drained uplift capacity of drilled shafts under repeated axial loading[J].Journal of Geotechnical Engineering,1990,116(3):470-491.
[13]LUTENEGGER A J,MILLER G A.Uplift capacity of small-diameter drilled shafts from In situ tests[J].Journal of Geotechnical Engineering,1994,120(8):1 362-1 380.
[14]吕凡任,陈仁朋,陈云敏,等.软土地基上微型桩抗压和抗拔特性试验研究[J].土木工程学报,2005,38(3):99-105.(LU Fanren,CHEN Renpeng,CHEN Yunmin,et al.Field tests on compression and uplift behavior of micropiles in soft ground[J].China Civil Engineering Journal,2005,38(3):99-105.(in Chinese))
[15]黄广龙,方乾,苏荣臻.软土地基微型桩抗拔试验研究[J].岩土工程学报,2010,32(11):1 788-1 793.(HUANG Guanglong,FANGQian,SU Rongzhen.Field test on uplift behavior of micropiles in soft ground[J].Chinese Journal of Geotechnical Engineering,2010,32(11):1 788-1 793.(in Chinese))
[16]徐再楼.灌注细石混凝土微型桩在软土地基上的抗拔性试验研究[J].公路工程,2016,41(5):222-225.(XU Zailou.Experimental study on uplift resistance of micropiles in soft soil foundation[J].Highway Engineering,2016,41(5):222-225.(in Chinese))
[17]陈伟志,蒋关鲁,袁泽华,等.低矮路堤下膨胀土地基现场浸水试验研究[J].岩石力学与工程学报,2014,33(8):1 609-1 618.(CHENWeizhi,JIANG Guanlu,YUAN Zehua,et al.Field soaking tests on expansive soil foundation under low embankment[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(8):1 609-1 618.(in Chinese))
[18]陈伟志.低矮路堤荷载下膨胀土地基胀缩变形特性研究[博士学位论文][D].成都:西南交通大学,2015.(CHEN Weizhi.Study on characteristics of swelling-shrinking deformation of expansive soil foundation under low embankment loading[Ph.D.Thesis][D].Chengdu:Southwest Jiaotong University,2015.(in Chinese))
[19]蒋关鲁,王海龙,李安洪.高速铁路路基基底应力计算方法研究[J].铁道建筑,2009,(4):65-69.(JIANG Guanlu,WANG Hailong,LI Anhong.Study on the base stresses calculation methods of high-speed railway subgrade[J].Railway Engineering,2009,(4):65-69.(in Chinese))
[20]蒋关鲁,王海龙,李安洪,等.土质路基荷载下地基反力试验研究[J].铁道学报,2012,34(6):69-74.(JIANG Guanlu,WANG Hailong,LI Anhong,et al.Experimental study on ground reaction under subgrade[J].Journal of the China Railway Society,2012,34(6):69-74.(in Chinese))
[21]蒋关鲁,王力伟,杭红星.路桥交界处地基附加应力修正计算方法[J].岩土工程学报,2013,35(2):208-218.(JIANG Guanlu,WANG Liwei,HANG Hongxing.The modified additional stress calculation method of bridge approach foundation under the subgrade load[J].Chinese Journal of Geotechnical Engineering,2013,35(2):208-218.(in Chinese))
[22]陈伟志,蒋关鲁,王智猛,等.分级连续加载条件下原状膨胀土固结变形研究[J].岩土力学,2014,35(3):710-716.(CHEN Weizhi,JIANG Guanlu,WANG Zhimeng,et al.Study of consolidation deformation of undisturbed expansive soil under stage continuous loading conditions[J].Rock and Soil Mechanics,2014,35(3):710-716.(in Chinese))
[23]郑健龙,张锐.公路膨胀土路基变形预测与控制方法[J].中国公路学报,2015,28(3):1-10.(ZHENG Jianlong,ZHANG Rui.Prediction and control method for deformation of highway expensive soil subgrade[J].China Journal of Highway and Transport,2015,28(3):1-10.(in Chinese))
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