基坑变形监测现场试验研究

结合浙江省桐乡市中虹天地商住楼基坑变形监测项目，研究了基坑沉桩挤土作用，分析了边长40cm方桩沉桩时，120倍桩径处地表仍有微弱隆起变形，以及基坑周边民住房的不均匀沉降变化特征。基坑开挖过程中，围护结构的受力状态发生改变，导致围护结构产生上浮现象。基坑土体水平位移随开挖深度增加逐渐变大，且在土体蠕变作用下，水平位移量仍会有所增加。大气降水导致基坑内外地下水位差变大，增加围护结构的侧压力。支撑轴力受混凝土凝固收缩、温差以及钢筋、混凝土之间的差异徐变影响，支撑轴力计算时需进行修正。

Field Experimental Study on Deformation Monitoring of Foundation Pit

Based on the deformation monitoring of foundation pit of zhong-hong-tian-di business-living building, in Tongxiang city, Zhejiang province. And soil-compacting during the pile-sinking construction is studied. The area is about 120 times of it＇s edge-length can come up uplift deformation, when the piles with 40 cm edge-length were pressed. And the variation of differential settlement of people-living houses around the foundation pit is analyzed. The stress state of retaining structure is changed, which causes the retaining structure appears floating phenomenon, during excavation of foundation pit. The horizon- tal displacement of soil becomes large in pace with the excavating depth of foundation pit, moreover, under the action of soil creep deformation, the horizontal displacement will become more large. In case of rainfall, groundwater level head inside and outside of foundation pit will increase, at the same time, basement retaining structure side pressure will increase, too. Support axial force can be affected by solidification contraction of concrete, temperature difference, different creep of concrete and rein-forcement. So the support axial force should be modified.