锚杆临界锚固长度解析计算
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摘要
采用理想弹塑性荷载传递函数,通过分析极限承载力与锚杆长度的关系,推导了锚杆临界锚固长度的解析算式,并在此基础上进一步分析了摩阻力分布、极限锚固力与锚固长度的关系。分析表明,当锚固长度小于工程临界锚固长度时,摩阻力分布较为均匀,而锚固长度的增加对极限承载力提高明显。基于这一点,建议锚杆的设计长度应小于工程临界锚固长度。为方便工程应用,还提出了工程临界锚固长度的理论计算方法和快速估算方法。
Up to now,the analytical estimation of critical anchorage length,which is a very important parameter in bolts design,is not available. A perfectl elasto-plastic load-transfer model is used to derive an analytical solution for this problem. Based on the developed analytical solution,an analytical critical anchorage length (ACAL) formulation,which relates the anchorage diameter,anchorage deformation modulus,and anchorage layer characteristic coefficient with the critical anchorage length,is obtained. The analytical solution also shows a trend of more uniform distribution of the frictional resistance when the anchorage length is less than ACAL. The frictional resistance distribution becomes very uneven when the anchorage length is larger than half of the ACAL. Further study shows that the ultimate bearing capacity of the bolt increases significantly as the anchorage length increases within half of the ACAL,while the anchorage length is larger than half ACAL the effect of anchorage length on bearing capacity is limited. Based on the above findings,it can be seen that half ACAL is a very important parameter indicating the efficiency of the bolts. Thus,it is defined as“engineering critical anchorage length”and it is suggested that the designed anchorage lengths of bolts should be below their engineering critical anchorage lengths. Two convenient methods for practical use of estimation of the engineering anchorage length are presented with examples.
Up to now,the analytical estimation of critical anchorage length,which is a very important parameter in bolts design,is not available. A perfectl elasto-plastic load-transfer model is used to derive an analytical solution for this problem. Based on the developed analytical solution,an analytical critical anchorage length (ACAL) formulation,which relates the anchorage diameter,anchorage deformation modulus,and anchorage layer characteristic coefficient with the critical anchorage length,is obtained. The analytical solution also shows a trend of more uniform distribution of the frictional resistance when the anchorage length is less than ACAL. The frictional resistance distribution becomes very uneven when the anchorage length is larger than half of the ACAL. Further study shows that the ultimate bearing capacity of the bolt increases significantly as the anchorage length increases within half of the ACAL,while the anchorage length is larger than half ACAL the effect of anchorage length on bearing capacity is limited. Based on the above findings,it can be seen that half ACAL is a very important parameter indicating the efficiency of the bolts. Thus,it is defined as“engineering critical anchorage length”and it is suggested that the designed anchorage lengths of bolts should be below their engineering critical anchorage lengths. Two convenient methods for practical use of estimation of the engineering anchorage length are presented with examples.
引文
[1]程良奎.岩土锚固的现状与发展[J].土木工程学报,2001,34(3):7–12.(Cheng Liangkui.Present status and development of ground anchorages[J].China Civil Engineering Journal,2001,34(3):7–12.(in Chinese))
[2]程良奎.我国岩土锚固技术的现状与发展[A].见:岩土工程中的锚固技术[C].北京:地震出版社,1992.(Cheng Liangkui.Present status and development of ground anchorage technique of China[A].In:Anchorage Technique in Geotechnical Engineering[C].Beijing:Earthquake Press,1992.(in Chinese))
[3]张乐文.岩土锚固理论研究之现状[J].岩土力学,2002,23(5):627–631.(Zhang Lewen.Research on status of anchorage theory of rock and soil[J].Rock and Soil Mechanics,2002,23(5):627–631.(in Chinese))
[4]Evangelista A,Sapio G.Behaviour of ground anchors in stiff clays[A].In:Proceedings of the9th International Conference on Soil Mechanics and Foundation Engineering[C].Tokyo:The Japanese Society of Soil Mechanics and Foundation Engineering,1977.39–47.
[5]Ostermayer H,Scheele F.Research on ground anchors in noncohesive soils[A].In:Proceedings of the9th International Conference on Soil Mechanics and Foundation Engineering[C].Tokyo:The Japanese Society of Soil Mechanics and Foundation Engineering,1977.92–97.
[6]陈广峰,米海珠.黄土地层中锚杆受力性能试验分析[J].甘肃工业大学学报,2003,29(1):116–119.(Chen Guangfeng,Mi Haizhu.Experimental analysis of anchor′s stress performance in collapsible loess layer[J].Journal of Gansu University of Technology,2003,29(1):116–119.(in Chinese))
[7]程良奎,胡建林.土层锚杆的几个力学问题[A].见;岩土工程中的锚固技术[C].北京:人民交通出版社,1996.(Cheng Liangkui,Hu Jianlin.Several mechanical problems in soil bolts[A].In:Anchorage Technique in Geotechnical Engineering[C].Beijing:China Communications Press,1996.)
[8]程良奎,范景伦,韩军等.岩土锚固[M].北京:中国建筑工业出版社,2002.(Cheng Liangkui,Fan Jinglun,Han Jun,et al.Soil and Rock Anchorage[M].Beijing:China Architecture and Building Press,2002.(in Chinese))
[9]孔宪宾,余跃欣,李炜等.土–锚杆相互作用机理的研究[J].工程力学,2000,17(3):80–86.(Kong Xianbin,She Yuexin,Li Wei,et al.The mechanism study of soil-anchor interaction[J].Engineering Mechanics,2000,17(3):80–86.(in Chinese))
[10]张季如,唐保付.锚杆荷载传递机理分析的双曲函数模型[J].岩土工程学报,2002,24(2):188–192.(Zhang Jiru,Tang Baofu.Hyperbolic function model to analyze load transfer mechanism on bolts[J].Chinese Journal of Geotechnical Engineering,2002,24(2):188–192.(in Chinese))
[2]程良奎.我国岩土锚固技术的现状与发展[A].见:岩土工程中的锚固技术[C].北京:地震出版社,1992.(Cheng Liangkui.Present status and development of ground anchorage technique of China[A].In:Anchorage Technique in Geotechnical Engineering[C].Beijing:Earthquake Press,1992.(in Chinese))
[3]张乐文.岩土锚固理论研究之现状[J].岩土力学,2002,23(5):627–631.(Zhang Lewen.Research on status of anchorage theory of rock and soil[J].Rock and Soil Mechanics,2002,23(5):627–631.(in Chinese))
[4]Evangelista A,Sapio G.Behaviour of ground anchors in stiff clays[A].In:Proceedings of the9th International Conference on Soil Mechanics and Foundation Engineering[C].Tokyo:The Japanese Society of Soil Mechanics and Foundation Engineering,1977.39–47.
[5]Ostermayer H,Scheele F.Research on ground anchors in noncohesive soils[A].In:Proceedings of the9th International Conference on Soil Mechanics and Foundation Engineering[C].Tokyo:The Japanese Society of Soil Mechanics and Foundation Engineering,1977.92–97.
[6]陈广峰,米海珠.黄土地层中锚杆受力性能试验分析[J].甘肃工业大学学报,2003,29(1):116–119.(Chen Guangfeng,Mi Haizhu.Experimental analysis of anchor′s stress performance in collapsible loess layer[J].Journal of Gansu University of Technology,2003,29(1):116–119.(in Chinese))
[7]程良奎,胡建林.土层锚杆的几个力学问题[A].见;岩土工程中的锚固技术[C].北京:人民交通出版社,1996.(Cheng Liangkui,Hu Jianlin.Several mechanical problems in soil bolts[A].In:Anchorage Technique in Geotechnical Engineering[C].Beijing:China Communications Press,1996.)
[8]程良奎,范景伦,韩军等.岩土锚固[M].北京:中国建筑工业出版社,2002.(Cheng Liangkui,Fan Jinglun,Han Jun,et al.Soil and Rock Anchorage[M].Beijing:China Architecture and Building Press,2002.(in Chinese))
[9]孔宪宾,余跃欣,李炜等.土–锚杆相互作用机理的研究[J].工程力学,2000,17(3):80–86.(Kong Xianbin,She Yuexin,Li Wei,et al.The mechanism study of soil-anchor interaction[J].Engineering Mechanics,2000,17(3):80–86.(in Chinese))
[10]张季如,唐保付.锚杆荷载传递机理分析的双曲函数模型[J].岩土工程学报,2002,24(2):188–192.(Zhang Jiru,Tang Baofu.Hyperbolic function model to analyze load transfer mechanism on bolts[J].Chinese Journal of Geotechnical Engineering,2002,24(2):188–192.(in Chinese))
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