为研究非平衡堆载作用下,地铁基坑施工过程不同特征剖面处的地表沉降的空间效应特性,以南昌市某地铁车站基坑工程为研究背景,利用PLAXIS 3D软件建立三维精细化数值模型进行模拟分析。模拟值与实测值吻合良好,验证了数值模拟的准确性。通过改变坑外非平衡堆载大小,开展了两种工况下的数值研究,在此基础上研究了不同情况下的坑外不同特征剖面处的地表沉降响应情况,探讨了不同非平衡堆载大小、降水方案情况下坑外地表沉降的空间效应。结果表明：非平衡堆载对基坑长边近堆载侧的地表沉降影响更大,近堆载侧地表沉降普遍大于远堆载侧；分步降水开挖工况下,坑外不同特征剖面处的地表沉降均较小,基坑分步降水开挖对坑外地表沉降有一定的抑制作用；非平衡堆载作用下,基坑坑外地表沉降分布具有显著的空间效应,一次性降水开挖各研究区域的地表沉降空间效应均大于分步降水开挖工况。

In order to study the spatial effect characteristics of surface settlement at different characteristic locations during subway pit construction under the action of non-equilibrium loading, a subway station pit project in Nanchang is taken as the background of the study, and a three-dimensional numerical model is established by using PLAXIS 3D software for simulation and analysis. The simulated values are in good agreement with the measured values, which verifies the accuracy of numerical simulation. By changing the size of the non-equilibrium loading outside the pit, numerical studies were carried out under two working conditions, on the basis of which the surface settlement response at different characteristic locations outside the pit under different conditions was studied. The spatial effects of surface settlement outside the pit under different non-equilibrium loading and dewatering schemes were discussed.The results show that non-equilibrium loading has a greater impact on the surface settlement on the long side of the foundation pit near the loading side, and the surface settlement on the near loading side is generally greater than the far loading side. Under the condition of step-by-step dewatering excavation, the surface settlement at different characteristic sections outside the pit is relatively small. Step-by-step dewatering excavation of the foundation pit has a certain inhibitory effect on the surface settlement outside the pit. under the action of non-equilibrium loading, the surface settlement distribution outside the foundation pit has a significant spatial effect. At the same time, the spatial effect of surface settlement in each study area of ??the one-time dewatering excavation was greater than that of the step-by-step dewatering excavation condition.

国家自然科学基金资助项目(52238009)；江西省自然科学基金–揭榜挂帅资助项目(20223BBG71018)；南昌轨道交通集团科研项目(2020HGKYB008)