基于模型试验的重力式锚碇极限承载性能研究

Study on Limit Bearing Feature of Gravity Anchorage Based on Model Test

锚碇结构作为悬索桥荷载传递的终端,其承载能力和可靠性至关重要。重力式锚碇因其对周围环境的依赖性低,适应范围较广,常作为大跨度悬索桥锚碇的选型。因此,针对重力式锚碇承载性能的研究至关重要。以云南省某特大桥宣威岸重力锚工程为依托,根据《公路悬索桥设计规范》和《公路桥涵与基础设计规范》中关于重力式锚碇的评价指标,通过模型试验和数值仿真两种手段,对宣威岸重力锚工程的极限承载力进行研究。根据实验室空间大小和试验需要,设计了模型箱,通过定滑轮控制入射角和转向,垂向施加砝码控制分级加载。同时,根据已知信息,在Flac3D下建立数值模型,锚碇和周围岩体使用薄层单元连接,底面边界采用固定约束,侧面采用法向约束,地表自由。锚碇选用弹性本构,岩土体采用Mohr-coulomb的弹塑性本构。所得主要结论如下:(1)通过模型试验水平位移揭示的锚碇极限承载力为12P,竖向位移揭示的锚碇极限承载力为14P,水平位移相对于竖向位移更敏感。(2)平底锚碇在14P后整体失稳,带齿坎锚碇达到极限后仍能保持整体稳定,齿坎有利于承载和整体稳定。(3)倾覆稳定性评价应增补倾斜控制标准。数值仿真结果呼应了模型试验结果,证明了模型试验结论的正确性,两类方法同时揭示了锚碇-地基联合承载的阶段特征。

As the terminal of load transfer in suspension bridge,the bearing capacity and reliability of anchorage structure are very important.Gravity anchorages are often selected for long-span suspension bridges because of their low dependence on the surrounding environment and wide range of adaptations.Therefore,the research on the bearing performance of gravity anchorage is very important.Based on the gravity anchorage project of Xuanwei shore of a grand bridge in Yunnan Province,according to the evaluation indicators of gravity anchorages in Specifications for Design of Highway Suspension Bridge and Specifications for Design of Foundation of Highway Bridges and Culverts,the ultimate bearing capacity of the abovementioned anchorage project is studied by means of by numerical simulation and model test.The model box is designed according to the size of the laboratory space and the needs of the experiment.The angle of incidence and the steering are controlled by the fixed pulley,and the vertical weight is applied to control the graded loading.At the same time,according to the known information,the numerical model is established in FLAC3 D.The anchorage and surrounding rock are connected by thin layer elements,the bottom boundary adopts fixed constraint,the side adopts normal constraint,and the ground surface is free.The anchorage adopts elastic constitutive model,and the rock and soil adopt Mohr-Coulomb elastic-plastic constitutive model.The main conclusions are as follows:(1)The ultimate bearing capacities of the anchorage revealed by the horizontal and vertical displacements in model test is 12 P and 14 P respectively,and horizontal displacement is more sensitive than vertical one.(2)The flat bottom anchorage is unstable after 14 P loading condition,but the anchorage with notches sill can maintain the overall stability after reaching the limit.The notches are conducive to the bearing capacity and overall stability.(3)The lean control indicator should be added in the overturn stability evaluation.The numerical simulation result is in line with the model test result,which proves the correctness of the model test conclusion.The stage characteristics of the anchorage-foundation joint bearing are revealed by the 2 methods.