考虑大气折光系数的三角高程测量在基坑监测中的应用

Application of Triangular Elevation Measurement Considering Atmospheric Refraction Coefficient in Foundation Pit Monitoring

在基坑开挖过程中,监测数据的准确性对保障基坑安全至关重要,本文以珠海市软土地区某基坑工程为例,通过对三角高程测量原理、误差来源进行论述和分析,提出了顾及大气折光系数的三角高程测量在基坑监测中的应用,并通过对比徕卡TM50全站仪中默认设置的大气折光系数κ=0.13与不同的大气折光系数κ对基坑立柱沉降监测的影响结果,得出以下结论:大气折光系数是影响三角高程测量精度的唯一可变因素;大气折光系数与三角高程测量结果呈线性关系;不同的大气折光系数会对监测结果产生较大的差异,进而造成数据出现“失真”现象。该结论可为三角高程测量在基坑监测中对竖向位移成果修正提供分析思路,也为跨江、悬崖、边坡和大型斜拉桥等特殊监测工程提供借鉴方法和研究。

During the excavation of the foundation pit,it is critical to ensuring the safety of foundation pits for the accuracy of monitoring data,this article takes a foundation pit project in the soft soil area of Zhuhai City as an example,through the discussion and analysis of the principle of triangular elevation measurement and the source of error,the application of triangular elevation measurement in consideration of atmospheric refractive index in foundation pit monitoring is proposed,and by comparing the atmospheric refractive coefficient κ=0.13 set by default in the Leica TM50 total station with different atmospheric refractive coefficient κ on the results of monitoring the settlement of foundation pit pillars,it is concluded as follow:atmospheric refractive index is the only variable factor affecting the accuracy of triangulation;Atmospheric refractive index is linearly related to triangular elevation measurements;Different atmospheric refraction coefficients will produce large differences in monitoring results,resulting in"distorted"data.This conclusion can provide analytical ideas for the correction of vertical displacement results in the monitoring of foundation pits by triangular elevation measurement,and also provides reference methods and research for special monitoring projects such as river crossings,cliffs,slopes and large cable-stayed bridges.