整体桥台后大不平衡土压力计算方法研究

Study on Calculation Method of Larger Unbalanced Earth Pressure of Backfill behind Abutment in Integral Abutment Jointless Bridges

为研究车辆重载等引起的台后大不平衡土压力的变化,通过开展有、无考虑台后大不平衡土压力影响的整体式桥台-H型钢桩-土相互作用拟静力试验研究,分析对比台后大不平衡土压力大小、分布规律及其计算方法。结果表明:在设置的试验条件下,随着位移荷载的增加,台后填土作用下整体式桥台-H型钢桩-土相互作用模型(AHP模型)台后土压力由三角形分布变为梯形分布;而台后大不平衡土压力下整体式桥台-H型钢桩-土相互作用模型(LAHP模型)台后土压力呈梯形分布。LAHP模型的台后土压力系数K整体上大于AHP模型。现有的台后土压力系数K计算方法不适用于整体桥。当δ/h=0.016时,AHP和LAHP模型的台后土压力系数分别为12.34和16.16,远大于JTG D60—2015《公路桥涵设计通用规范》中主动土压力系数(K_(ac)=0.24)和静止土压力系数(K_(0)=0.43),也远大于现有的计算方法(Coulomb被动土压力系数K_(pC)=9.96和Rainkine被动土压力系数K_(pR)=3.69)。本研究可为整体桥设计计算和相关规范的制定提供借鉴和参考。

In order to study the variation of larger unbalanced earth pressure of backfill behind abutment caused by vehicle load,several reciprocating low-cycle pseudo-static tests on interaction of soil-abutment-steel H-pile with or without considering the effect of unbalanced earth pressure of backfill behind abutment were carried out.A comparative study was performed to find magnitude,distribution law and calculation method of larger unbalanced earth pressure of backfill behind abutment.The test results indicated that under the test conditions of this study,with the increase of displacement load,the distribution law of earth pressure for the abutment-steel H-pile interaction under backfill behind abutment(AHP model)changed from“triangle“distribution to“trapezoidal”distribution.The distribution law of earth pressure for the abutment-steel H-pile interaction under larger unbalanced earth pressure of backfill behind abutment(LAHP model)was a"trapezoidal"distribution.The earth pressure coefficient for LAHP model was larger than that of AHP model under the reciprocating displacement loading.The existing calculation method of earth pressure coefficient K was not applicable to IAJBs.The earth pressure coefficient of AHP and LAHP models were 12.34 and 16.16 respectively.They were significantly larger than active earth pressure coefficient(K_(ac)=0.24)and earth pressure coefficient at rest(K_(0)=0.43)from the code of General Specifications for Design of Highway Bridges and Culverts(JTG D60—2015)as well as the Coulomb theory(K_(pC)=9.96)whenδ/h reached 0.016(δ/h=0.016).In addition,the existing calculation method of earth pressure coefficient K was also larger than the existing theoretical calculation methods(the Rankine theory K_(PR)=3.69).In addition,the relevant research in this study could provide reference for the design and calculation and the formulation of relevant specifications in IAJBs.