工程勘察报告尚不能正确提供各类土层的水平基床系数，而现有规程和指南给出的基坑土层水平反力系数的比例系数m值参考范围较大，致使设计中对m值的选取存在很大的随意性。通过假设及简化分析，提出一个综合考虑土体重度、基坑开挖深度、土层水平反力系数和抗剪强度指标的基坑土层等效m值计算公式，并利用水平位移实测数据，通过非参数回归方法反演确定系数Δ1、Δ2，以修正等效m值计算公式。以昆明市某浅埋公路隧道工程为例，对该反演方法进行分析验证。验证结果表明，该方法不仅能缩小规程或指南给定的m值取值区间，还可以根据基坑开挖深度不断地修正基坑土层等效m值，实现基坑动态控制。

At present, the horizontal subgrade coefficient of all kinds of soil can not be correctly provided in the engineering investigation report. The m values referenced from existing regulations and guidelines are always in a wide range, which leads to great randomness and variability for the selection of m value in design. On the basis of hypothesis and simplified analysis, the formula for calculating the equivalent m value of foundation pit soil layer is provided, which considers soil gravity, excavation depth, lateral earth pressure coefficient and shear strength. By using the measured horizontal displacement monitoring data, the nonparametric regression method is used to back analyze the coefficient Δ1 and Δ2 to correct the formula of the equivalent m value. Taking a shallow highway tunnel in Kunming for example, the back analysis method is analyzed and verified. The results show that the method can not only reduce the m value range given by the regulations or guidelines and improve the calculation precision, but also can constantly modify the equivalent m value of the foundation pit soil according to the depth of the foundation pit, and then realize the dynamic control of the foundation pit.