喀斯特地区短桩锚杆复合基础现场抗拔试验及设计方法研究
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摘要
针对喀斯特地区输电线路工程中普遍存在的上覆厚土层(4~7m)、下卧中等风化及以上岩石的特殊地基条件,提出一种短桩锚杆复合基础。为了揭示复合基础的承载机制,建立相应的工程设计方法,推动这种新型基础在工程中的应用,选取位于广东阳春典型喀斯特地区的上覆粉质黏土、下卧微风化石灰岩的地基作为试验现场,依据我国110~1 000 kV电压等级输电杆塔承受的上拔荷载,设计出6个不同入土深度、不同锚筋数量的1∶1全尺寸短桩和复合基础,通过开展现场抗拔承载特性试验,获得试验基础的荷载位移曲线、抗拔承载力、地基破坏模式等规律,进一步揭示复合基础的抗拔承载机制;结合现场试验结果与理论分析,提出复合基础的失效是由其下部锚杆基础破坏时对应的上拔位移所控制,在此基础上建立复合基础抗拔承载力的计算公式,并给出复合基础失效位移以及承载力分配系数的确定方法。通过与现场试验结果的对比,验证所给方法的正确性,为该类新型基础在工程中的推广应用提了理论依据。
In this paper,a composite foundation combining short pile and anchor was proposed for the complex foundation conditions with overlying thick soil layer(4–7 m) and underlying moderately weathered rock in the Karst area for overhead transmission line project. In order to reveal the bearing mechanism of the composite foundation and to establish the corresponding design method to facilitate the better application to projects,the foundation with overlying silty clay and underlying weakly weathered limestone at the typical Karst area of Yangchuan in Guangdong province was selected as the site of field test. Six full-size foundations(1∶1) with different embedded depths and different anchor numbers were designed according to the uplift load on the tower hanging the transmission line of 110–1 000 kV voltage in China. The load-displacement curves,ultimate uplift bearing capacities and foundation failure modes of the tested foundations were obtained in the pull-out tests on the site. It was concluded from the test results and theoretical analysis that the failure of the composite foundation is controlled by the ultimate uplift displacement when the anchor appears damaged. On this basis,a formula for calculating the uplift bearing capacity of the composite foundation was established,and the methods to determine the failure displacement and the allocation coefficients of bearing capacity of the composite foundation were proposed respectively. The correctness of the methods was verified by comparing with the field test results.
In this paper,a composite foundation combining short pile and anchor was proposed for the complex foundation conditions with overlying thick soil layer(4–7 m) and underlying moderately weathered rock in the Karst area for overhead transmission line project. In order to reveal the bearing mechanism of the composite foundation and to establish the corresponding design method to facilitate the better application to projects,the foundation with overlying silty clay and underlying weakly weathered limestone at the typical Karst area of Yangchuan in Guangdong province was selected as the site of field test. Six full-size foundations(1∶1) with different embedded depths and different anchor numbers were designed according to the uplift load on the tower hanging the transmission line of 110–1 000 kV voltage in China. The load-displacement curves,ultimate uplift bearing capacities and foundation failure modes of the tested foundations were obtained in the pull-out tests on the site. It was concluded from the test results and theoretical analysis that the failure of the composite foundation is controlled by the ultimate uplift displacement when the anchor appears damaged. On this basis,a formula for calculating the uplift bearing capacity of the composite foundation was established,and the methods to determine the failure displacement and the allocation coefficients of bearing capacity of the composite foundation were proposed respectively. The correctness of the methods was verified by comparing with the field test results.
引文
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[21]崔强,孟宪乔,杨少春.扩径率与入岩深度对岩基挖孔基础抗拔承载特性影响的试验研究[J].岩土力学,2016,37(增2):195–202.(CUI Qiang,MENG Xianqiao,YANG Shaochun. Experimental investigation of influence of embedment depth in rock and expanding ratio upon ultimate uplift resistance of hole digging foundation in rock[J].Rock and Soil Mechanics,2016,37(Supp.2):195–202.(in Chinese))
[22]史佩栋.桩基工程手册[M].北京:人民交通出版社,2009:59–66.(SHIPeidong.Pileandpilefoundationhandbook[M].Beijing:China Communication Press,2009:59–66.(in Chinese))
[23]崔强,杨文智.短桩–岩石锚杆复合基础研究[R].北京:中国电力科学研究院,2017.(CUI Qiang,YANG Wenzhi. Technical report on composite foundation of short pile and rock bolt research[R]. Beijing:China Electric Power Research Institute,2017.(in Chinese))
[2]KIMDH,LEESR.Upliftcapacityoffixedshallowanchors subjectedtoverticalloadinginrock[J].InternationalJournalof Offshore and Polar Engineering,2005,15(4):312–320.
[3]PARK J H,QIU T,ASCE M. et al. Field and laboratory investigation ofpulloutresistanceofsteelanchorsinrock[J].JournalofGeotechnical and Geoenvironmental Engineering,2013,139(12):2 219–2 224.
[4]PARK J,QIU T,KIM Y. A field investigation of pullout resistance of steel anchors in rock[C]//MAGUED I,JOHN E G,MOHAMAD H H.FromSoilBehaviorFundamentalstoInnovationsinGeotechnical Engineering. Atlanta Georgia:ASCE Press,2014:609–616.
[5]程永锋,鲁先龙,郑卫锋.输电线路工程岩石锚杆基础的应用[J].电力建设,2012,33(5):12–16.(CHENG Yongfeng,LU Xianlong,ZHENGWeifeng.Applicationof rockanchor foundation intransmission line[J]. Electric Power Construction,2012,33(5):12–16.(in Chinese))
[6]程永锋,赵江涛,鲁先龙,等.特高压直流输电线路岩石锚杆群锚基础试验[J].中国电力,2014,47(12):55–60.(CHENG Yongfeng,ZHAO Jiangtao,LU Xianlong,et al. Field full-scale tests on group anchorage rock foundations of DC UHV transmission line project[J].Electric Power,2014,47(12):55–60.(in Chinese))
[7]汪德敏.灰岩地区承台式群锚桩基础上拔试验研究[J].电力学报,2015,30(6):534–540.(WANGDemin.Researchonuplifttestof group anchor piles with bearing platform in limestone area[J]. Journal of Electric Power,2015,30(6):534–540.(in Chinese))
[8]张德才.浅谈掏挖式基础在输电线路上的应用[J].广东电力,2000,13(4):25–26.(ZHANGDecai.Dredgedfoundationappliedto transmission lines[J]. Guangdong Electric Power,2000,13(4):25–26.(in Chinese))
[9]鲁先龙,乾增珍,崔强.黄土地基掏挖扩底基础抗拔试验研究[J].岩土力学,2014,35(3):647–652.(LU Xianlong,QIAN Zengzhen,CUI Qiang. Experimental investigation on uplift behavior of belled piers in loess[J]. Rock and Soil Mechanics,2014,35(3):647–652.(in Chinese))
[10]刘洪义.一种新型复合基础方案及其试验研究[J].吉林电力,2011,39(3):7–10.(LIU Hongyi. A new type of compound foundation plananditsexperimentalresearch[J].JilinElectricPower,2011,39(3):7–10.(in Chinese))
[11]丁士君,金建华,鲁先龙.输电线路新型复合式基础的设计与应用[J].武汉大学学报,2011,44(增):210–213.(DING Shijun,JIN Jianhua,LU Xianlong. Design and application of novel composite foundationstotransmissionlines[J].EngineeringJournalofWuhan University,2011,44(Supp.):210–213.(in Chinese))
[12]程永锋,鲁先龙,丁士君,等.掏挖与岩石锚杆复合型杆塔基础抗拔试验与计算[J].电力建设, 2012, 33(3):6–10.(CHENG Yongfeng,LUXianlong,DINGShijun,etal.Experimentaland computational research on the uplift of composite foundation of belled pierandrockanchorintransmissionlineengineering[J].Electric Power Construction,2012,33(3):6–10.(in Chinese))
[13]郑卫锋,杨文智,刘利民.输电线路复合型基础的应用研究[J].电力建设,2012,33(9):11–14.(ZHENG Weifeng,YANG Wenzhi,LIU Limin. Study on application of composite foundation in transmission line[J]. Electric Power Construction,2012,33(9):11–14.(in Chinese))
[14]鞠彦忠,孙鹏,张显峰,等.输电线路新型复合式基础试验及计算方法探讨[J].水电能源科学, 2012,30(6):169–171.(JU Yanzhong,SUNPeng,ZHANGXianfeng,etal.Experimentand calculationmethodstudyonanewcompositefoundationfor transmission lines engineering[J]. Water Resources and Power,2012,30(6):169–171.(in Chinese))
[15]中华人民共和国国家标准编写组.GB50021—2001岩土工程勘察规范(2009年版)[S].北京:中国建筑工业出版社,2010.(The National Standards Compilation Group of People′s Republic of China.GB50021—2001Codeforinvestigationofgeotechnicalengineering(2009)[S]. Beijing:China Construction Industry Press,2010.(in Chinese))
[16]中华人民共和国国家标准编写组.GB50266—2013工程岩体试验方法标准[S].北京:中国计划出版社,2013.(The National Standards CompilationGroupofPeople′sRepublicofChina.GB50266—2013Standard for test methods of engineering rock mass[S]. Beijing:China Planning Press,2013.(in Chinese))
[17]中华人民共和国标准编写组.GB/T50218—2014工程岩体分级标准[S].北京:中国计划出版社,2014.(TheNationalStandards CompilationGroupofPeople′sRepublicofChina.GB/T50218—2014Standardforengineeringclassificationofrockmasses[S].Beijing:China Planning Press,2014.(in Chinese))
[18]国家电网公司.国家电网公司输变电工程通用设计:输电线路掏挖基础分册[M].北京:中国电力出版社,2018:3–6.(StateGrid CorporationofChina.Thegeneraldesignofpowertransmission projectofSGCC:Transmissionlinediggedfoundationfascicle[M].Beijing:China Electric Power Press,2018:3–6.(in Chinese))
[19]中华人民共和国行业标准编写组.JGJ106—2014建筑基桩检测技术规范[S]:北京:中国建筑工业出版社,2014.(TheProfessional StandardsCompilationGroupofPeople′sRepublicofChina.JGJ106—2014 Technical code for testing of building foundation piles[S]. Beijing:China Building Industry Press,2014.(in Chinese))
[20]中华人民共和国行业标准编写组.DL/T5219—2014架空输电线路基础设计技术规程[S].北京:中国电力出版社, 2015.(The ProfessionalStandardsCompilationGroupofPeople′sRepublicof China. DL/T 5219—2014 Technical code for design of foundation of overhead transmission line[S]. Beijing:China Eclectic Power Press,2015.(in Chinese))
[21]崔强,孟宪乔,杨少春.扩径率与入岩深度对岩基挖孔基础抗拔承载特性影响的试验研究[J].岩土力学,2016,37(增2):195–202.(CUI Qiang,MENG Xianqiao,YANG Shaochun. Experimental investigation of influence of embedment depth in rock and expanding ratio upon ultimate uplift resistance of hole digging foundation in rock[J].Rock and Soil Mechanics,2016,37(Supp.2):195–202.(in Chinese))
[22]史佩栋.桩基工程手册[M].北京:人民交通出版社,2009:59–66.(SHIPeidong.Pileandpilefoundationhandbook[M].Beijing:China Communication Press,2009:59–66.(in Chinese))
[23]崔强,杨文智.短桩–岩石锚杆复合基础研究[R].北京:中国电力科学研究院,2017.(CUI Qiang,YANG Wenzhi. Technical report on composite foundation of short pile and rock bolt research[R]. Beijing:China Electric Power Research Institute,2017.(in Chinese))