带EPS的整体式桥台-桩-土相互作用拟静力试验
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摘要
整体桥中台后土压力在温度循环作用下会发生较大变化,这种季节性横向土压力的变化在每次温度循环后会持续增大,其实际所受水平土压力会远大于桥台设计时的压力,同时桥台桩基会产生累积和残余变形,因而有效减少台后土压力与桥台桩基的累积和残余变形至关重要。为此以桥台-H形钢桩试件为研究对象,通过在桥台侧向施加水平位移荷载,开展带膨胀聚苯乙烯(EPS)填料板的整体式桥台-桩-土往复荷载拟静力试验,分析桥台、桩基的骨架曲线、滞回曲线及其沿入土深度方向的水平变形和桥台转角等的变化规律,初步研究EPS填料板的厚度对桥台-桩基-土相互作用受力性能的影响。试验结果表明:在台后埋设EPS填料板能有效减小上部结构变形时桥台所受到的水平力,最大可减小31%;同时,也可减小模型试件的累积变形,其随着EPS厚度的增加而逐渐减小,尤其对桩的累积变形减小最为显著,最大减小了74.3%;在台后埋设EPS填料板也可有效减小台后填土对桥台转角的约束作用;台后埋设EPS填料板会使单步位移荷载作用下产生的变形有所增大,但幅度不大;试验全过程各模型试件均表现出了良好的弹性性能和变形能力。
The earth pressure of backfill behind the abutment of integral abutment jointless bridge(IAJB) varies substantially as the bridge girder is easily subjected to load due to cycling temperature. This earth pressure that increases continuously due to seasonal variations in temperature, results in the actual earth pressure of the backfill is much larger than the designed earth pressure, and the accumulative deformations in abutment and pile emerge. Therefore, the crucial problems with IAJBs include effectively reducing the earth pressure behind the abutment, eliminating the accumulative deformation, and reducing the horizontal thrust of the girder under temperature load. Based on the specimens of abutment H-shaped steel pile, a low-cyclic, pseudo-static experiment was carried out on abutment pile soil interactions in IAJBs that incorporate expanded polystyrenes(EPS). The hysteresis curves and their skeletons of the abutment and pile, the horizontal deformations along the depth direction of the soil, and the angles of the abutments were achieved. The influence on abutment-pile-soil interaction behavior was preliminarily studied by different thickness of EPS fillers. The results of these investigations indicate that the horizontal thrust on the abutment due to girder expansion is reduced effectively after the burial of the EPS fillers behind the abutment. Specifically, the thrust reduces 31 % when the thickness of the EPS filling is 15 cm. The accumulative deformation of the pile and abutment decreases as the thickness of the EPS filling increases, especially at the depth of 0.4 m below the top of the pile, where the deformation reduces 74.3 %. In addition, the EPS filling behind the abutment remarkably reduces the constraints on the rotation angle by the backfill. Nevertheless, the deformations under a single step of displacement loading increase by a small amount after the burial of the EPS fillers. These fillers provide adequate elasticity and flexibility, and they exhibit reasonable mechanical properties under cycling temperature loads.
The earth pressure of backfill behind the abutment of integral abutment jointless bridge(IAJB) varies substantially as the bridge girder is easily subjected to load due to cycling temperature. This earth pressure that increases continuously due to seasonal variations in temperature, results in the actual earth pressure of the backfill is much larger than the designed earth pressure, and the accumulative deformations in abutment and pile emerge. Therefore, the crucial problems with IAJBs include effectively reducing the earth pressure behind the abutment, eliminating the accumulative deformation, and reducing the horizontal thrust of the girder under temperature load. Based on the specimens of abutment H-shaped steel pile, a low-cyclic, pseudo-static experiment was carried out on abutment pile soil interactions in IAJBs that incorporate expanded polystyrenes(EPS). The hysteresis curves and their skeletons of the abutment and pile, the horizontal deformations along the depth direction of the soil, and the angles of the abutments were achieved. The influence on abutment-pile-soil interaction behavior was preliminarily studied by different thickness of EPS fillers. The results of these investigations indicate that the horizontal thrust on the abutment due to girder expansion is reduced effectively after the burial of the EPS fillers behind the abutment. Specifically, the thrust reduces 31 % when the thickness of the EPS filling is 15 cm. The accumulative deformation of the pile and abutment decreases as the thickness of the EPS filling increases, especially at the depth of 0.4 m below the top of the pile, where the deformation reduces 74.3 %. In addition, the EPS filling behind the abutment remarkably reduces the constraints on the rotation angle by the backfill. Nevertheless, the deformations under a single step of displacement loading increase by a small amount after the burial of the EPS fillers. These fillers provide adequate elasticity and flexibility, and they exhibit reasonable mechanical properties under cycling temperature loads.
引文
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[15] 史佩栋.桩基工程手册[M].北京:人民交通出版社,2015.SHI Pei-dong.Pile and Pile Foundation Hand-book [M].Beijing:China Communications Press,2015.
[2] GIRTON D D,HAWKINSON T R,GREIMANN L F.Validation of Design Recommendations for Integral-abutment Piles [J].Journal of Structural Engineering 1991,117 (7):2117-2134.
[3] FAR N E.MALEKI S,BARGHIAN M.Design of Integral Abutment Bridges for Combined Thermal and Seismic Loads [J].Earthquakes and Structures,2015,9 (2):415-430.
[4] CIVJAN S A,BONCZAR C,BRENA S F.Integral Abutment Bridge Behavior:Parametric Analysis of a Massachusetts Bridge [J].Journal of Bridge Engineering,2007,12 (1):64-71.
[5] 黄福云,林友炜,程俊峰,等.整体式桥台-H型钢桩-土相互作用低周往复拟静力试验研究 [J].中国公路学报,2019,32(5):100-114.HUANG Fu-yun,LIN You-wei,CHENG Jun-feng,et al.Study on Interaction of Integral Abutment-H-Shaped Steel Pile-soil Under Reciprocating Low-cycle Pseudo-Static Test [J].Chinese Journal of Highway and Transport,2019,32 (5):100-114.
[6] DARLEY P,CARDER D R,BARKER K J.Seasonal Thermal Effects over Three Years on the Shallow Abutment of an Integral Bridge in Glasgow [R].London:Transport Research Laboratory,1998.
[7] MARURI R F,PETRO S H.Integral Abutments and Jointless Bridges (IAJB) 2004 Survey Summary [C] // IAJB.Integral Abutment and Jointless Bridges (IAJB 2005).Washington DC:FHWA,2005:12-29.
[8] YU Tian-lai,LIU Yang,LI Bai-yan.The Computing Mode of Earth Pressure Behind the Abutment with Increasing Temperature [J].Advanced Materials Research,2012,368:312-316.
[9] REID R A,SOUPIR S P,SCHAEFER V R.Mitigation of Void Development Under Bridge Approach Slabs Using Rubber Tire Chips [C] // ASCE.Recycled Materials in Geotechnical Applications.Reston:ASCE,1998:37-50.
[10] HORVATH J S.Controlled Yielding Using Geofoam Compressible Inclusions:New Frontier in Earth Retaining Structures [M].Washington DC:Geotechnical Engineering for Transportation,2004.
[11] EDWARD J H.Field Study of Integral Back-wall with Elastic Inclusion,2004 Survey Summary [R].Washington DC:FHWA,2005.
[12] 陈晓冬.季节性温度荷载下整体式桥台桥梁的台后土压力研究[D].福州:福州大学,2002.CHEN Xiao-dong.Study on Soil Pressure of Seasonal Temperature Load of Integral Abutment Bridges [D].Fuzhou:Fuzhou University,2002.
[13] HORVATH J S.Integral-abutment Bridges:Geotechnical Problems and Solutions Using Geo-synthetics and Ground Improvement [D].Morgantown:West Virginia University,2005.
[14] 庄一舟,黄福云,钱海敏,等.PHC管桩-土相互作用受力性能拟静力试验[J].中国公路学报,2017,30(4):42-51.ZHUANG Yi-zhou,HUANG Fu-yun,QIAN Hai-min,et al.Pseudo-static Test Research on Mechanic Behavior of PHC Piles with Soil-pile Interaction [J].China Journal of Highway and Transport,2017,30 (4):42-51.
[15] 史佩栋.桩基工程手册[M].北京:人民交通出版社,2015.SHI Pei-dong.Pile and Pile Foundation Hand-book [M].Beijing:China Communications Press,2015.