考虑地层应变软化的盾构下穿密集建筑物沉降分析

Settlement Analysis of Dense Buildings Under-passed by Shield Tunnel Considering Stratum Strain Softening

针对砂质地层中盾构连续下穿密集建筑物变形问题,考虑应变软化效应,依托南宁地铁5号线五一立交站—新秀公园站区间隧道工程,通过ABAQUS的VUMAT用户接口编程实现基于摩尔-库伦的应变软化本构模型,采用数值计算分析盾构连续下穿密集建筑物的地表变形及建筑物不均匀沉降规律。结果表明:应变软化本构模型能较真实地反映砂质地层的变形特性,计算结果与监测数据吻合良好;建筑物引起的沉降槽之间相互叠加导致周围地表沉降增大,且对地表纵向沉降影响明显,叠加效应随建筑物净距增大而减弱;盾构施工中建筑物的不均匀沉降值最大,前侧存在地面超载将导致该值增大;施工完成时的不均匀沉降与建筑物两侧地面超载分布形式关系密切,非对称较对称工况不均匀沉降更明显。

In view of the deformation problem of dense buildings continuously under-passed by shield tunnel in sandy stratum,taking the tunnel engineering between Wuyi Interchange Station and Xinxiu Park Station of Nanning Metro Line 5 as background and considering the stratum strain softening effect,the strain softening constitutive model based on M-C was programmed by VUMAT of ABAQUS. The surface deformation and uneven settlement law of dense buildings under-passed by shield tunnel was analyzed with the use of numerical simulation. The results indicate that the strain softening constitutive model can truly reflect the deformation characteristics of sandy stratum,and the calculated results are in good agreement with the measured data. The superposition of the settlement troughs caused by buildings leads to the increase of the surrounding surface settlement,and has a significant impact on the longitudinal settlement of the surface. The superposition effect weakens with the increase of the net span of the buildings. The uneven settlement value of the building during shield construction is the largest,and the existence of ground overload on the front will cause this value to increase. The uneven settlement after the completion of shield construction is closely related to the distribution of ground overload on both sides of the building,and the uneven settlement under asymmetric condition is more obvious than that under symmetric condition.