不同载荷边界条件下的地铁站深基坑变形特性研究

袁庆利

摘要：为更好地实现不同载荷边界条件下的基坑变形预测和控制，以天津市某地鐵站深基坑为研究对象，研究超载、卸载条件下基坑变形特征。通过对现场监测数据的分析，推导基坑北侧和南侧的变形规律，并将分析结果与无超载、卸载条件的普通基坑进行水平位移、地表沉降、土体蠕变等方面的对比，最后，根据超载与卸载产生主动土压力对水平位移的影响，制定了基坑变形控制措施。结果表明：1）载荷边界条件对基坑支护结构和地层的变形影响明显;2）北侧基坑围护结构的水平位移和地表沉降均远大于南侧，北侧变形常超过变形报警值，南侧则相反;3）北侧土层水平蠕变最大速率和竖向蠕变最大速率均大于基坑南侧，普通基坑水平蠕变的最大速率介于两者之间，表明控制边界载荷有利于控制土层变形速率;4）基坑北侧的主动土压力明显高于基坑南侧，由于卸荷作用，基坑南侧地连墙底部产生被动土压力，使基坑侧壁向迎土侧移动;5）合理安排开挖进度，加强支承刚度，减少地表超载，是控制荷载边界条件和基坑变形的有力措施。研究可为城区复杂荷载边界作用下的基坑监测、施工的优化提供依据。

关键词：地基基础工程;荷载边界条件;深基坑;变形特性;天津地铁

中图分类号：TU476文献标识码：ADOI： 10.7535/hbgykj.2021yx03008

Abstract：In order to predict and control the deformation of subway foundation pit under different load boundary conditions， the deformation characteristics of foundation pit were studied in a case of Tianjin metro under overloading and unloading conditions. Based on the analysis of field monitoring data， the deformation laws of the foundation pit were deduced in the north and south sides， then the results were compared with the ordinary foundation pit without overloading and unloading conditions in the aspects of horizontal displacement， settlement and soil creep.  Finally， according to the influence of the active earth pressure generated by overload and unload on the horizontal displacement， the deformation control measures were formulated. The results show that： 1） the deformation of supporting structure and stratum of foundation pit is obviously influenced by the load boundary conditions ; 2） the horizontal displacement and settlement of the retaining structure in the north side are much larger than those in the south side， and the deformation often exceeds the alarm value in the north side， while that in the south side is on the contrary; 3） the maximum rates of soil horizontal creep and vertical creep in the north side are higher than those of the south side， between which is the maximum rate of soil horizontal creep of ordinary foundation pit， indicating that the control of boundary load is good for controlling the soil deformation rate; 4） the active earth pressure on the north side is significantly higher than that on the south side. The passive earth pressure is generated at the bottom of the diaphragm wall on the south side due to the unloading effect， which makes the diaphragm wall move towards the soil side; 5） reasonable arrangement of excavation schedule， strengthening of support stiffness and reduction of surface overload are effective measures to control load boundary conditions and foundation pit deformation. The research result provides some reference for foundation pit monitoring and construction optimization under complex load boundary in urban area.

Keywords：ground foundation engineering; load boundary conditions; deep foundation pit; deformation characteristics; Tianjin Metro

地铁深基坑的建设会受到周边环境的影响，特别是在城区密集建筑物以及市政设施的影响下，地铁的深基坑开挖具有高风险和高难度的特点，对基坑建设本身和周边建（构）筑物、周边交通、居民行人等都具有潜在的安全隐患[1-2]。……