软土深基坑的空间变形特性分析及危险性评估

Spatial deformation characteristics analysis and risk assessment of deep foundation pit in soft soil

为准确掌握软土深基坑的变形特性,并合理评价其危险性,基于现场监测成果,进行基坑重要监测项目的空间变形特征分析;通过变形分级和发展趋势判据计算得到相应特征指标,从而开展基坑危险性评估。结果表明:支护结构的空间变形近似呈“驼峰”特征,即基坑两端头的变形值相对较小,而基坑中部的变形值相对较大;周边土体沉降相对较小,随着与基坑距离的增加,地表沉降呈下降趋势,且随基坑持续施工,不同深度处的土体侧位移也随之增加,侧位移最大值均明显大于其他监测项目的变形值;通过变形分级判据得到深层侧位移的危险性等级相对最高,其次是墙顶变形和地表沉降,危险性等级为Ⅲ级;通过发展趋势判据,得到基坑趋势等级相对较低,仅为2级;根据不利原则叠加,确定安元西路站基坑的危险性评估等级为Ⅲ级,属预警状态。

In order to accurately grasp the deformation characteristics of deep foundation pit in the soft soil and reasonably evaluate its risk,based on the on-site monitoring results,the analysis on the spatial deformation characteristics of important monitoring items of the foundation pit was carried out.The corresponding characteristics indexes were calculated and obtained through the deformation classification criteria and development trend criteria,thus to carry out the risk assessment of foundation pit.The results showed that the spatial deformation of the supporting structure approximately presented the"hump"characteristic,that is,the deformation values at both ends of the foundation pit were relatively small,while the deformation value at the middle of the foundation pit was relatively large.The surrounding soil settlement was relatively small,with the increase of the distance from foundation pit,the ground settlement presented a descending trend,and as the construction of foundation pit continued,the lateral displacement of soil at different depths also increased,and the maximum lateral displacement was significantly greater than the deformation values of other monitoring items.Through the deformation classification criteria,it was obtained that the risk level of deep lateral displacement was relatively the highest,followed by the wall top deformation and the surface settlement,which was grade III.Through the development trend criteria,it was obtained that the trend level of foundation pit was relatively low,which was only grade 2.Both of them were superimposed according to the unfavorable principle,and the risk assessment level of the foundation pit in Anyuan West Road Station was determined to be level III,which was an early warning state.