加卸载工况下的车站深基坑开挖变形性状研究

某地铁车站深基坑北侧邻近新建住宅高楼,南侧毗邻另一个在挖基坑。以该车站基坑开挖为背景,通过分析基坑的实测数据,重点研究基坑在此特殊工况下其南北两侧围护墙水平位移和地表沉降的差异以及建筑物沉降和立柱沉降。分析实测数据可得:北侧围护墙水平位移和地表沉降均大于南侧,且常常超过变形报警值;北侧坑壁上的主动土压力大于南侧坑壁所受主动土压力,又由于周边卸载导致南侧墙底产生被动土压力,使得其向坑外偏移;北侧坑壁土体最大水平蠕变率和最大地表沉降蠕变率均略大于南侧;周边高楼沉降以及立柱沉降均在报警值以内,其中高楼沉降均匀,而由于南侧的开挖卸载,立柱的隆起也不明显。

Research on Deformation Behavior of Deep Foundation Pit Excavation of Station under Loading and Unloading Conditions

A deep foundation pit of a metro station is adjacent to the new residential high-rise buildings on the north side, and is adjacent to the other one foundation pit under excavation on the south side. Taking this foundation pit of station as the background, through the analysis of the measured data of the foundation pit, the study focus is on the difference between the horizontal displacement and ground surface settlement of the retaining wall on the north and south sides of the foundation pit, and the settlements of the buildings and the stand columns under this special constructing condition. The measured analysis data show that the horizontal displacement and ground surface settlement of the retaining wall on the north side are larger than on the south side, and often exceed the deformation alarm value. The active earth pressure on the north pit wall is greater than on the south pit wall. And because of the surrounding unloading, the passive earth pressure is generated at the bottom of the south side wall, which makes it drift out of the pit. The maximum horizontal creep rate and the maximum ground settlement creep rate of the soil on the north pit wall are slightly larger than those on the south side. The settlement of surrounding high-rise buildings and the settlement of the stand columns are all within the alarm value, in which the settlement of the high-rise buildings is even. Due to the excavation and unloading on the south side, the uplift of the stand column is not obvious.