[提要]  从理论上分析了m值的适用性和按规范方法确定拂值的局限性，指出了采用规范方法时应遵循的原则和注意的问题，最后用试验结果和实测数据证明采用旁压试验和位移反分析方法是准确确定优值的有效方法。
[关键词]  基坑 围护工程 水平抗力系数  位移反分析

This paper analyzed the applicability of "m" value and limits of determining "m" value based on code. It
also pointed out the principle and the problems. Finally, it proved with experimental data and results that PMT and back-analysis from displacement are efficient to determine "m"value accurately.
Keywords: foundation  pits; retaining structure; lateral  resistance  coefficient; back-analysis; displacement