土工格栅加筋砂土复合体极限承载能力分析
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摘要
土工合成材料加筋土桥台可以有效减小桥梁与路基之间的差异沉降,避免"桥头跳车"现象的发生。为了计算土工合成材料加筋土复合体在设计中承受荷载的安全冗余度,对其极限承载能力进行了分析。首先讨论了评价加筋土复合体极限承载能力的计算公式,并提出了该公式是否适用于评价加筋细颗粒土复合体承载性能的问题。然后在平面应变的条件下,进行了5组土工格栅加筋砂土模型试验和1组无加筋模型试验,考虑了加筋间距和筋材强度对加筋砂土复合体极限承载能力的影响,并将试验结果与公式的计算结果进行对比,发现该公式低估了加筋砂土的承载能力。基于莫尔库仑破坏准则,并假定加筋土的破坏面符合朗肯破坏面,提出了预测加筋砂土极限承载能力的分析模型,并将模型的计算值与试验值进行对比,发现两者基本吻合。
The differential settlement generated between the bridge deck and the approaching road willn be eliminated and bridge jump will also be prevented if geosynthetic-reinforced soil abutment is employed. To calculate its safety redundancy in the design, the ultimate bearing capacity of the geosynthetic-reinforced soil composite needs to be computed. Firstly, the model for calculating the ultimate bearing capacity of the geosynthetic-reinforced soil mass proposed by Wu and Pham is analyzed,and whether this model has the capability to predict the ultimate bearing capacity of geosynthetic-reinforced fine grained soil is questioned. To verify this problem, five geogrid-reinforced sand model tests and one unreinforced soil model test are then conducted under plain strain condition. The effects of reinforcement spacing and strength on the ultimate bearing capacity of the geosynthetic-reinforced soil are considered in the model tests. A comparison is made between the test results and those calculated using the model proposed by Wu and Pham. It is found out that the model proposed by Wu and Pham underestimates the ultimate bearing capacity of the geogrid-reinforced sand. Finally, a new analytical model is put forward based on the failure criterion of Mohr-Coulomb and the assumption of Rankine failure surface. The results calculated using the proposed model are coincident well with those obtained from the model tests.
The differential settlement generated between the bridge deck and the approaching road willn be eliminated and bridge jump will also be prevented if geosynthetic-reinforced soil abutment is employed. To calculate its safety redundancy in the design, the ultimate bearing capacity of the geosynthetic-reinforced soil composite needs to be computed. Firstly, the model for calculating the ultimate bearing capacity of the geosynthetic-reinforced soil mass proposed by Wu and Pham is analyzed,and whether this model has the capability to predict the ultimate bearing capacity of geosynthetic-reinforced fine grained soil is questioned. To verify this problem, five geogrid-reinforced sand model tests and one unreinforced soil model test are then conducted under plain strain condition. The effects of reinforcement spacing and strength on the ultimate bearing capacity of the geosynthetic-reinforced soil are considered in the model tests. A comparison is made between the test results and those calculated using the model proposed by Wu and Pham. It is found out that the model proposed by Wu and Pham underestimates the ultimate bearing capacity of the geogrid-reinforced sand. Finally, a new analytical model is put forward based on the failure criterion of Mohr-Coulomb and the assumption of Rankine failure surface. The results calculated using the proposed model are coincident well with those obtained from the model tests.
引文
[1]ADAMS M T,NICKS J E,STABILE T,et al.Geosynthetic reinforced soil integrated bridge system interim implementation guide[R].Final Report,FHWA-HRT-11-026.McLean:Federal Highway Administration,2011.
[2]ADAMS M T,NICKS J E,STABILE T,et al.Geosynthetic reinforced soil integrated bridge system synthesis report[R].Final Report,FHWA-HRT-11-027.McLean:Federal Highway Administration,2011.
[3]SAGHEBFAR M,ABU-FARSAKH M,ARDAH A,et al.Performance monitoring of geosynthetic reinforced soil integrated bridge system(GRS-IBS)in Louisiana[J].Geotextiles and Geomembranes,2017,45(2):34-47.
[4]HELWANY S M B,WU J H T,FROESSL B.GRS bridge abutments-and effective means to alleviate bridge approach settlement[J].Geotextiles and Geomembranes,2003,21(3):177-196.
[5]BERG R R,CHRISTOPHER B R,SAMTANI N.Design and construction of mechanically stabilized earth walls and reinforced soil slopes-VolumeⅠ[R].W C:Dept.ashington Dof Transportation,2009.
[6]ELTON D J,PATAWARAN M A B.Mechanically stabilized earth reinforcement tensile strength from tests of geotextile-reinforced soil[R].Washington D C:Transportation research record 1868,Transportation research board,2005.
[7]ADAMS M T,KETCHART K,WU J T H.Mini pier experiments:geosynthetic reinforcement spacing and strength as related to performance[C]//Geosynthetics in Reinforcement and Hydraulic Applications,Geotechnical Special Publication 165,Geo-Denver 2007,ASCE.Reston,2007.
[8]WU J T H,LEE K Z Z,PHAM T.Allowable bearing pressures of bridge sills on GRS abutments with flexible facing[J].Journal of Geotechnical and Geoenvironmental Engineering,2006,132(7):830-841.
[9]WU J T H,PHAM T Q.Load-carrying capacity and required reinforcement strength of closely spaced soil-geosynthetic composites[J].Journal of Geotechnical and Geoenvironmental Engineering,2013,139(9):1468-1476.
[10]LADE,P V,LEE K L.Engineering properties of soils[R].Report UCLA-ENG-7652,Department of Civil Engineering,University of California.Los Angeles,1976.
[11]ADIB M E.Internal lateral earth pressure in earth walls[D].University of California.Berkeley,1988.
[2]ADAMS M T,NICKS J E,STABILE T,et al.Geosynthetic reinforced soil integrated bridge system synthesis report[R].Final Report,FHWA-HRT-11-027.McLean:Federal Highway Administration,2011.
[3]SAGHEBFAR M,ABU-FARSAKH M,ARDAH A,et al.Performance monitoring of geosynthetic reinforced soil integrated bridge system(GRS-IBS)in Louisiana[J].Geotextiles and Geomembranes,2017,45(2):34-47.
[4]HELWANY S M B,WU J H T,FROESSL B.GRS bridge abutments-and effective means to alleviate bridge approach settlement[J].Geotextiles and Geomembranes,2003,21(3):177-196.
[5]BERG R R,CHRISTOPHER B R,SAMTANI N.Design and construction of mechanically stabilized earth walls and reinforced soil slopes-VolumeⅠ[R].W C:Dept.ashington Dof Transportation,2009.
[6]ELTON D J,PATAWARAN M A B.Mechanically stabilized earth reinforcement tensile strength from tests of geotextile-reinforced soil[R].Washington D C:Transportation research record 1868,Transportation research board,2005.
[7]ADAMS M T,KETCHART K,WU J T H.Mini pier experiments:geosynthetic reinforcement spacing and strength as related to performance[C]//Geosynthetics in Reinforcement and Hydraulic Applications,Geotechnical Special Publication 165,Geo-Denver 2007,ASCE.Reston,2007.
[8]WU J T H,LEE K Z Z,PHAM T.Allowable bearing pressures of bridge sills on GRS abutments with flexible facing[J].Journal of Geotechnical and Geoenvironmental Engineering,2006,132(7):830-841.
[9]WU J T H,PHAM T Q.Load-carrying capacity and required reinforcement strength of closely spaced soil-geosynthetic composites[J].Journal of Geotechnical and Geoenvironmental Engineering,2013,139(9):1468-1476.
[10]LADE,P V,LEE K L.Engineering properties of soils[R].Report UCLA-ENG-7652,Department of Civil Engineering,University of California.Los Angeles,1976.
[11]ADIB M E.Internal lateral earth pressure in earth walls[D].University of California.Berkeley,1988.