桩承式路堤土拱效应形成机制离散元模拟
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摘要
针对桩承式路堤,分别建立二维和三维离散元分析模型,开展土拱形成过程数值模拟。从细观角度研究不同路堤高度条件下桩承式路堤土拱形态和荷载传递机制,获得土拱效应充分发挥条件下的土体沉降模式,其模式呈现为椭圆形拱状。二维分析结果表明,当路堤填土高度达到一定值时,其高度约为0.8倍桩净距。由于二维土拱模型只能反映一个截面上的土拱效应,因而高估了路堤荷载传递效率。相比二维Trapdoor分析结果,三维条件下土拱效应充分发挥时所需的桩-土差异沉降更大,桩顶和桩间土压力随差异沉降的变化速率更慢,荷载传递效率更低且受填土高度影响更高。
Two-dimensional and three-dimensional discrete element models were established to study the formation of soil arching in a pile-supported embankment. The shape of soil arch and the load transferring mechanism of pile-supported embankment under different embankment height were investigated from microscopic point of view, and the obtained settlement profile of soil shows an elliptical mode. In the two-dimensional case, the height of soil arch is about 0.8 times of the pile spacing, as long as the embankment fill is thick enough. Since two-dimensional model can only reflect the soil arching effect in a cross section, the load transfer efficiency of the embankment will be overestimated. Compared with the two-dimensional case, the full mobilization of soil arching under three-dimensional condition requires a larger differential settlement, the changing rate of the soil pressures on the pile and subsoil with differential deformation becomes slower, the load transfer efficiency is lower, and the soil height becomes more affected by the embankment height.
Two-dimensional and three-dimensional discrete element models were established to study the formation of soil arching in a pile-supported embankment. The shape of soil arch and the load transferring mechanism of pile-supported embankment under different embankment height were investigated from microscopic point of view, and the obtained settlement profile of soil shows an elliptical mode. In the two-dimensional case, the height of soil arch is about 0.8 times of the pile spacing, as long as the embankment fill is thick enough. Since two-dimensional model can only reflect the soil arching effect in a cross section, the load transfer efficiency of the embankment will be overestimated. Compared with the two-dimensional case, the full mobilization of soil arching under three-dimensional condition requires a larger differential settlement, the changing rate of the soil pressures on the pile and subsoil with differential deformation becomes slower, the load transfer efficiency is lower, and the soil height becomes more affected by the embankment height.
引文
[1] 吕玺琳,马泉,方航.高铁桩网复合结构软土路基长期运营沉降模型试验研究[J].岩土工程学报,2017,39(S1):140-144
[2] 吕玺琳,马泉.高铁复合结构路基荷载传递及沉降数值模拟[J].铁道工程学报,2018,35(7):1-6.
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[10] Chevalier B,Combe G,Villard P.Experimental and discrete element modeling studies of the trapdoor problem:influence of the macromec-hanical frictional parameters[J].Acta Geotechnica,2012,7(1):15-39.
[11] Chen Y M,Cao W P,Chen R P.An experimental investigation of soil arching within basal reinforced and unreinforced piled embankments[J].Geotextiles and Geomembranes,2008,26(2):164-174.
[12] 赖汉江,郑俊杰,章荣军,等.桩承式路堤土拱形成及荷载传递机制离散元分析[J].岩土力学,2015,36(S1):646-650.
[13] 韩高孝,宫全美,周顺华.摩擦型岩土材料土拱效应微观机制颗粒流模拟分析[J].岩土力学,2013,34(6):1791-1798.
[14] Le Hello B,Villard P.Embankments reinforced by piles and geosynthetics-numerical and experimental studies dealing with the transfer of load on the soil embankment[J].Engineering Geology,2009,106(1-2):78-91.
[15] Thornton C.Numerical simulations of deviatoric shear deformation of granular media[J].Géotechnique,2000,50(1):43-53.
[16] Zhou W,Liu J,Ma G,et al.Macroscopic and microscopic behaviors of granular materials under proportional strain path:a DEM study[J].International Journal for Numerical and Analytical Methods in Geomechanics,2016,40(18):2450-2467.
[17] Jiang M J,Konrad J M,Leroueil S.An efficient technique for generating homogeneous specimens for DEM studies[J].Computers and Geotechnics,2003,30(7):579-597.
[2] 吕玺琳,马泉.高铁复合结构路基荷载传递及沉降数值模拟[J].铁道工程学报,2018,35(7):1-6.
[3] Terzaghi K.Theoretical SOIL mechanics[M].Chapman and Hali,Limited John Wiler and Sons,Inc;New York,1944.
[4] Ladanyi B,Hoyaux B.A study of the trap-door problem in a granular mass[J].Canadian Geotechnical Journal,1969,6(4):441-443.
[5] Moradi G,Bonab M H,Abbasnejad A.Experimental modeling and measuring stresses and strains during arching phenomenon[J].Geosciences,2015,5(2):53-61.
[6] Rui R,Van Tol A F,Xia Y Y,et al.Investigation of soil-arching development in dense sand by 2D model tests[J].Geotechnical Testing Journal,2016,39(3):415-430.
[7] Hewlett W J,Randolph M F.Analysis of piled embankments[J].Ground Engineering,1988,21(3):12-18.
[8] Russell D,Pierpoint N.An assessment of design methods for piled embankments[J].Ground Engineering,1997,30(10):39-44.
[9] Son M.Three-dimensional expansion of the terzaghi arching formula considering inclined sliding surfaces and examination of its effects[J].International Journal of Geomechanics,2016,17(7):06016043.
[10] Chevalier B,Combe G,Villard P.Experimental and discrete element modeling studies of the trapdoor problem:influence of the macromec-hanical frictional parameters[J].Acta Geotechnica,2012,7(1):15-39.
[11] Chen Y M,Cao W P,Chen R P.An experimental investigation of soil arching within basal reinforced and unreinforced piled embankments[J].Geotextiles and Geomembranes,2008,26(2):164-174.
[12] 赖汉江,郑俊杰,章荣军,等.桩承式路堤土拱形成及荷载传递机制离散元分析[J].岩土力学,2015,36(S1):646-650.
[13] 韩高孝,宫全美,周顺华.摩擦型岩土材料土拱效应微观机制颗粒流模拟分析[J].岩土力学,2013,34(6):1791-1798.
[14] Le Hello B,Villard P.Embankments reinforced by piles and geosynthetics-numerical and experimental studies dealing with the transfer of load on the soil embankment[J].Engineering Geology,2009,106(1-2):78-91.
[15] Thornton C.Numerical simulations of deviatoric shear deformation of granular media[J].Géotechnique,2000,50(1):43-53.
[16] Zhou W,Liu J,Ma G,et al.Macroscopic and microscopic behaviors of granular materials under proportional strain path:a DEM study[J].International Journal for Numerical and Analytical Methods in Geomechanics,2016,40(18):2450-2467.
[17] Jiang M J,Konrad J M,Leroueil S.An efficient technique for generating homogeneous specimens for DEM studies[J].Computers and Geotechnics,2003,30(7):579-597.