考虑填土强度的加筋土挡墙动位移计算
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摘要
加筋土挡墙在地震荷载作用下的位移大小对结构的抗震性能影响显著。为了计算地震荷载作用下加筋土挡墙的位移,Newmark滑块法通常被用于设计中。由于传统的Newmark滑块法在计算中忽略了填土强度的变化,因而采用单一峰值或残余强度的计算将可能导致计算得到的位移小于或大于实际位移值。在二楔块破坏模式的假定条件下,根据楔块的力学平衡条件,建立了加筋土挡墙滑动安全系数计算式,同时通过引入位移阈值考虑了填土的应变软化特点。通过将计算结果与模型试验结果对比,得到以下结论:相较于单楔块法,二楔块法更能真实地反映出墙体的实际破坏模式,且计算得到的屈服加速度系数更接近试验值;相较于采用单一峰值或残余强度计算的位移,考虑填土应变软化的计算解更接近于模型测试值。
The displacements of reinforced soil retaining walls under seismic loads have a significant influence on their seismic performances. In order to calculate the displacements under earthquakes, Newmark's sliding block method is usually used in design.As the traditional Newmark's sliding block method neglects changes of soil strength, so the peak or residual strength is used in calculation, which lead to the calculated values being smaller or bigger than the actual values. Under the assumption of a two-wedge failure mechanism, sliding safety coefficient of reinforced earth retaining walls is obtained using the mechanical equilibrium equations of wedges. At the same time, the strain softening characteristic of backfills is considered by introducing thresholds of displacements. The following conclusions have been obtained by comparing the calculated values with the model tests. Compared with the single wedge method, the two-wedge method can better describe the actual failure mode of model walls and the calculated yield acceleration coefficient is closer to the test values. Compared with the calculated displacements by using the peak or residual strength, the calculated values from the proposed method where strain softening is considered is closer to the model test values.
The displacements of reinforced soil retaining walls under seismic loads have a significant influence on their seismic performances. In order to calculate the displacements under earthquakes, Newmark's sliding block method is usually used in design.As the traditional Newmark's sliding block method neglects changes of soil strength, so the peak or residual strength is used in calculation, which lead to the calculated values being smaller or bigger than the actual values. Under the assumption of a two-wedge failure mechanism, sliding safety coefficient of reinforced earth retaining walls is obtained using the mechanical equilibrium equations of wedges. At the same time, the strain softening characteristic of backfills is considered by introducing thresholds of displacements. The following conclusions have been obtained by comparing the calculated values with the model tests. Compared with the single wedge method, the two-wedge method can better describe the actual failure mode of model walls and the calculated yield acceleration coefficient is closer to the test values. Compared with the calculated displacements by using the peak or residual strength, the calculated values from the proposed method where strain softening is considered is closer to the model test values.
引文
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[12]张建经,韩鹏飞.重力式挡墙基于位移的抗震设计方法研究--大型振动台模型试验研究[J].岩土工程学报,2012,34(3):417-423.ZHANG Jian-jing,HAN Peng-fei.Displacement based seismic design method for gravity retaining walls-large scale shaking table tests[J].Chinese Journal of Geotechnical Engineering,2012,34(3):417-423.
[13]LING H I.Recent applications of sliding block theory to geotechnical design[J].Soil Dynamics and Earthquake Engineering,2001,21(3):189-197.
[14]JR KAVAZANJIAN E,GIROUD J P.Newmark seismic deformation analysis for geosynthetic covers[J].Geosynthetics International,1998,5(8):1-2.
[15]HORII K,KISHIDA H,TATEYAMA M,et al.Computerized design method for geosynthetic-reinforced soil retaining walls for railway embankments[C]//Proceedings of Seiken Symposium No.11.Tokyo:[s.n.],1992.
[16]EL-EMAM M M,BATHURST R J.Facing contribution to seismic response of reduced-scale reinforced soil walls[J].Geosynthetics International,2005,12(5):215-238.
[17]TATSUOKA F,SAKAMOTO M,KAWAMURA T,et al.Strength and deformation characteristics of sand in plane strain compression at extremely low pressures[J].Soils and Foundations,1986,26(1):65-84.
[18]MATSUO O,YOKOYAMA K,SAITO Y.Shaking table tests and analyses of geosynthetic-reinforced soil retaining walls[J].Geosynthetics International,1998,5(1-2):97-126.
[19]TATSUOKA F.Seismic stability against high seismic loads of geosynthetic-reinforced soil retaining structures,Keynote Lecture[C]//Proceedings of 6th International Conference on Geosynthetics.Atlanta:Industrial Fabrics Association International,1998,1:103-142.
[20]NAKAJIMA S,HONG K,MULMI S,et al.Study on seismic performance of geogrid reinforced soil retaining walls and deformation characteristics of backfill soil[M]//Geosynthetics in Civil and Environmental Engineering.Berlin:Springer,2008:211-215.
[2]LING H I,LESHCHINSKY D,CHOU N N S.Postearthquake investigation on several geosyntheticreinforced soil retaining walls and slopes during the Ji-Ji earthquake of Taiwan[J].Soil Dynamics and Earthquake Engineering,2001,21(4):297-313.
[3]朱宏伟,姚令侃,张旭海.两种加筋土挡墙的动力特性比较及抗震设计建议[J].岩土工程学报,2012,34(12):2073-2080.ZHU Hong-wei,YAO Ling-kan,ZHANG Xu-hai.Comparison of dynamic characteristics between netted and packaged reinforced soil retaining walls and recommendations for seismic design[J].Chinese Journal of Geotechnical Engineering,2012,34(12):2073-2080.
[4]LING H I,LIU H,MOHRI Y.Parametric studies on the behavior of reinforced soil retaining walls under earthquake loading[J].Journal of Engineering Mechanics,2005,131(10):1056-1065.
[5]蒋建清,杨果林.格宾加筋土挡墙抗震性能及数值分析[J].土木工程学报,2012,45(1):100-108.JIANG Jian-qing,YANG Guo-lin.Numerical analysis of seismic behaviour of gabion-reinforced soil retaining wall[J].China Civil Engineering Journal,2012,45(1):100-108.
[6]汪益敏,BATHURST R J.振动条件下EPS缓冲层对挡土墙受力与变形影响的水平条分法模型研究[J].土木工程学报,2008,41(10):73-80.WANG Yi-min,BATHURST R J.Horizontal slice method for force and displacement analysis of EPSgeofoam seismic buffers for rigid retaining walls[J].China Civil Engineering Journal,2008,41(10):73-80.
[7]程亚男,孙树林,阮晓波,等.加筋土挡墙地震稳定性的拟动力分析[J].岩土力学,2013,34(12):3573-3579.CHENG Ya-nan,SUN Shu-lin,RUAN Xiao-bo,et al.Pseudo-dynamic analysis of seismic stability of reinforced soil walls[J].Rock and Soil Mechanics,2013,34(12):3573-3579.
[8]BHATTACHARJEE A,KRISHNA A M.Strain behavior of backfill soil in rigid faced reinforced soil walls subjected to seismic excitation[J].International Journal of Geosynthetics and Ground Engineering,2015,1(2):1-14.
[9]王丽艳,陈国兴,井合进.地震作用下土工格栅加筋土挡墙水平变形的拟静力计算法[J].中国公路学报,2015,28(3):28-34.WANG Li-yan,CHEN Guo-xing,JING He-jin.Pseudo-static method for horizontal displacement of geo-grid reinforced soil retaining wall under earthquake[J].China Journal of Highway and Transport,2015,28(3):28-34.
[10]AUSILIO E,CONTE E,DENTE G.Seismic stability analysis of reinforced slopes[J].Soil Dynamics and Earthquake Engineering,2000,19(3):159-172.
[11]HUANG C C,CHOU L H,TATSUOKA F.Seismic displacements of geosynthetic-reinforced soil modular block walls[J].Geosynthetics International,2003,10(1):2-23.
[12]张建经,韩鹏飞.重力式挡墙基于位移的抗震设计方法研究--大型振动台模型试验研究[J].岩土工程学报,2012,34(3):417-423.ZHANG Jian-jing,HAN Peng-fei.Displacement based seismic design method for gravity retaining walls-large scale shaking table tests[J].Chinese Journal of Geotechnical Engineering,2012,34(3):417-423.
[13]LING H I.Recent applications of sliding block theory to geotechnical design[J].Soil Dynamics and Earthquake Engineering,2001,21(3):189-197.
[14]JR KAVAZANJIAN E,GIROUD J P.Newmark seismic deformation analysis for geosynthetic covers[J].Geosynthetics International,1998,5(8):1-2.
[15]HORII K,KISHIDA H,TATEYAMA M,et al.Computerized design method for geosynthetic-reinforced soil retaining walls for railway embankments[C]//Proceedings of Seiken Symposium No.11.Tokyo:[s.n.],1992.
[16]EL-EMAM M M,BATHURST R J.Facing contribution to seismic response of reduced-scale reinforced soil walls[J].Geosynthetics International,2005,12(5):215-238.
[17]TATSUOKA F,SAKAMOTO M,KAWAMURA T,et al.Strength and deformation characteristics of sand in plane strain compression at extremely low pressures[J].Soils and Foundations,1986,26(1):65-84.
[18]MATSUO O,YOKOYAMA K,SAITO Y.Shaking table tests and analyses of geosynthetic-reinforced soil retaining walls[J].Geosynthetics International,1998,5(1-2):97-126.
[19]TATSUOKA F.Seismic stability against high seismic loads of geosynthetic-reinforced soil retaining structures,Keynote Lecture[C]//Proceedings of 6th International Conference on Geosynthetics.Atlanta:Industrial Fabrics Association International,1998,1:103-142.
[20]NAKAJIMA S,HONG K,MULMI S,et al.Study on seismic performance of geogrid reinforced soil retaining walls and deformation characteristics of backfill soil[M]//Geosynthetics in Civil and Environmental Engineering.Berlin:Springer,2008:211-215.