基坑开挖卸荷引起的公路桥梁桩基变形受力响应  

Stress Response of Pile Foundation Deformation of Highway Bridge Caused by Unloading of Pit Excavation

作　　者：杨涛[1] 童立元[1] 李丹 YANG Tao;TONG Li-yuan;LI Dan(School of Transportation,Southeast University,Nanjing 210096,Jiangsu,China;Nanjing Urban Public Project Construction Center,Nanjing 210019,Jiangsu,China)

机构地区：[1]东南大学交通学院,江苏南京210096 [2]南京市公共工程建设中心,江苏南京210019

出　　处：《建筑科学与工程学报》2020年第5期214-222,共9页Journal of Architecture and Civil Engineering

基　　金：国家自然科学基金项目(41572273,51878157);江苏省自然科学基金项目(BK20181282)。

摘　　要：采用两阶段分析法分析基坑开挖卸荷作用下公路桥梁的受力变形规律,首先基于明德林解析解,利用复合辛普森公式进行数值积分求解得出基坑侧壁卸荷与坑底卸荷同时作用下土体内桩体位置处的水平附加应力;其次采用Kerr三参数地基模型建立公路桥梁桩基的挠曲微分方程,结合水平附加应力,利用有限差分数值计算方法得到桩基挠曲微分方程的数学解析矩阵表达式。利用所得计算公式对公路桥梁桩基附近有基坑开挖的工况进行计算,并通过与数值模拟计算结果的对比验证所提计算方法的有效性;最后针对桩基轴向荷载大小、基坑与桩基距离及基坑三维尺寸进行了影响因素分析。结果表明:桩基轴向荷载的变化对桩基水平位移及桩身弯矩影响不明显;随着桩基与基坑距离的加大,桩基水平位移及最大弯矩逐渐减小,并且在较大距离范围内桩基水平位移及弯矩变化愈发平缓;开挖深度对桩基水平位移及弯矩的影响远大于开挖长度和开挖宽度,基坑开挖宽度对桩基的影响最小。The two-stage analysis method was used to analyze the stress and deformation law of highway bridge pile foundation under unloading of foundation pit excavation.The first stage of the two-stage method was based on the Mindlin solution.Using the composite Simpson formula to solve the numerical integration,the horizontal additional stress at the pile position in the soil under the simultaneous action of the side wall unloading and the bottom unloading of the foundation pit was obtained.In the second stage,Kerr three parameter foundation model was used to establish the deflection differential equation of highway bridge pile foundation.Combined with the horizontal additional stress,the mathematical analytic matrix expression of the differential equation of pile deflection was obtained by using the finite difference numerical calculation method.The calculation formula was used to calculate the excavation condition of foundation pit near the pile foundation of highway bridge,and the validity of the calculation method was verified by comparing with the numerical simulation results.The influence factors of axial load of pile foundation,distance between foundation pit and pile foundation and three-dimensional dimension of foundation pit were analyzed.The results show that the change of axial load of pile foundation has no obvious effect on the horizontal displacement and bending moment of pile body.With the increase of the distance between the pile foundation and the foundation pit,the horizontal displacement and the maximum bending moment of the pile foundation decrease gradually,and the change of the horizontal displacement and bending moment of the pile foundation becomes more and more gentle in a large range.The influence of excavation depth on horizontal displacement and bending moment of pile foundation is far greater than that of excavation length and width,and the influence of excavation width of foundation pit on pile foundation is the least.

关 键 词：基坑开挖 水平附加应力 有限差分法 两阶段分析法 

分 类 号：TU473[建筑科学—结构工程]