桥头路堤-桥台-地基作用体系的地震反应分析

Analysis of abutment-embankment-foundation interaction system subjected to seismic load

考虑桥头路堤、桥台、地基相互作用,建立路桥过渡段三维动力分析模型,输入汶川地震波,进行非线性地震反应时程分析。将数值计算结果,与经典理论和规范方法计算结果、离心试验结果,以及震害调查资料对比分析,证实计算模型和计算方法的合理性。着重计算桥头路堤、桥台、地基的地震位移反应,桥台的地震加速度、土压力、弯矩以及基底剪应力反应等。计算结果表明:震后桥台整体背离路堤滑移,并伴随下沉和外倾,地震位移包含平移与转动2部分,桥台顶部加速度存在放大效应,承受的地震土压力以及弯矩内力较震前明显增大,相比而言,公路规范与铁路规范方法的计算值偏小;震后桥头路堤向桥台方向推移,存在拉裂趋势和不均匀沉降破坏;地基与桥台基础相邻部位,峰值水平位移与残余水平位移以及最终沉降量相对较大,基底剪力大幅增加,桥台与地基出现相对滑移。研究结果对桥梁抗震加固设计具有借鉴意义。

A three-dimensional non-linear numerical model of approach embankment was established considering abutment-embankment-foundation interaction,and the Wenchuan earthquake wave was used as seismic load to carry out the non-linear time history analyses of seismic response.Comparing the results of numerical calculation with those of classical theory and standard method,centrifugal test results and seismic damage investigation data,the rationality of the calculation model and method was verified.The main analyses included the seismic displacement responses of embankment,abutment and foundation,seismic accelerations,earth pressure,bending moments and base shear stress response of abutment.The results show that the abutment deviated from the embankment,accompanied with sinking and extroversion after earthquake,and the seismic displacements included translation and rotation.The acceleration at the top of the abutment appeared amplification effect,and the seismic earth pressure and bending moments were obviously increased compared with those before earthquake.Comparatively,the calculation results by highway code and railway code method appeared to be smaller.After earthquake,the main seismic damage behaviors in approach embankment were crack and differential settlement;The peak and residual horizontal displacement,and final settlement of foundation soil adjacent to abutment were relatively large,and the shear force between the foundation and abutment increased greatly in earthquake which led to a relative slip.The results in this paper will be beneficial to seismic reinforcement design of bridges.