大面积堆载下软土区桥梁桩基变形机理及预防措施研究  

Deformation mechanism of bridge pile foundation in soft soil under large-scale surcharge load and its preventive measures

作　　者：马迪[1] 李双龙 魏丽敏[2] 何群[2] MA Di;LI Shuanglong;WEI Limin;HE Qun(Section of State-owned Assets Management,Shanxi Normal University,Xi’an 710119,China;School of Civil Engineering,Central South University,Changsha 410075,China;College of Water Conservancy and Ecological Engineering,Nanchang Institute of Technology,Nanchang 330099,China)

机构地区：[1]陕西师范大学国有资产管理处,陕西西安710119 [2]中南大学土木工程学院,湖南长沙410075 [3]南昌工程学院水利与生态工程学院,江西南昌330099

出　　处：《铁道科学与工程学报》2023年第11期4151-4162,共12页Journal of Railway Science and Engineering

基　　金：国家自然科学基金资助项目(51878671);江西省教育厅科学技术研究项目(GJJ2201509)。

摘　　要：软土区大面积堆载极易引发桥梁桩基时效性横向变形,但其变形机理及预防措施目前仍缺乏深入研究。依托典型堆载致桥墩偏移工程案例,开展固结-蠕变试验阐明软土时效性变形特征,比选最佳描述模型。将一维KOPPEJAN模型扩展至三维形式,基于ABAQUS平台开发对应用户材料子程序,并将其应用至有限元模型中。基于已验证的有限元模型,研究桩基响应及桩侧横向附加荷载时效性变化规律,进一步考察微型隔离桩和应力释放孔对桩基偏移的主动防控效果,据此提出适用工程建议。研究结果表明:相比MESRI模型和TIME-HARDENING模型,一维KOPPEJAN模型更适合描述该场地软土时效性变形特征,改进的扩展KOPPEJAN模型可以较好地还原该工程桩基桥墩的时效性偏移过程;随着堆载时间的延长,软土侧向变形持续增大,桩侧横向附加荷载持续增加至趋于稳定,但其沿深度的分布基本不变,主要分布在软弱土层内(4.0~32.0 m);深厚软土条件下,尽管微型隔离桩能够改善该桥梁桩基的受力行为,但很难将该承台偏移量控制在8.0 mm以内;采用孔深与软土厚度相同的应力释放孔可以减小承台偏移量60%以上,达到较好防治效果,但应注意应力释放和桩顶荷载联合作用引发的反向扰曲变形,建议钻孔施工完成后及时进行回填处理。研究成果可为主动防控堆载引发的墩台偏移等病害提供理论指导。Large-scale surcharge loads in soft soil areas frequently trigger time-dependent lateral deformation of bridge pile foundations,and its deformation mechanism and preventive measures still lack in-depth research.In this paper,based on a typical case of bridge pier deflection caused by surcharge load,consolidation-creep tests were carried out to illustrate the time-dependent deformation characteristic of the soft soil,and the best descriptive model was selected by comparison.The one-dimensional KOPPEJAN model was extended to a three-dimensional form,and the corresponding user-material subroutine was developed based on the ABAQUS platform.The subroutine was applied to a numerical model.Based on the validated numerical model,the time-dependent variation of the pile foundation response and the lateral additional load acting on the pile side were investigated.In addition,the preventive effect of micropiles and stress release holes on the pile foundation deflection was further investigated.Some applicable engineering recommendations were proposed accordingly.The results show that the one-dimensional KOPPEJAN model is more suitable than the MESRI and TIME-HARDENING models for characterizing the soft soil time-dependent deformation at the engineering site.The extended KOPPEJAN model can well reproduce the deflection process of the piled bridge piers.With the increase in loading time,the lateral deformation of soft soil continues to increase,and the lateral additional load acting on the pile side continued to increase until it stabilized,but its distribution along the depth is unchanged,which is mainly distributed within the soft soil layer(4.0~32.0 m in this paper).For deep soft soil conditions,although micropiles can improve the force behavior of pile foundations,it is difficult to correct the deflection of the cap within 8.0 mm.The application of stress release holes with the same depth as the thickness of the soft soil layer can reduce the cap deflection by more than 60%,realizing a better control effect.But attention

关 键 词：桥梁桩基 大面积堆载 变形机理 微型隔离桩 应力释放孔 

分 类 号：TU473[建筑科学—结构工程]