受开挖卸荷影响，硐壁表层岩体与深部未扰动岩体的变形特性会有所差异。现有规程在处理变形试验数据时，没有考虑这一差异，将承压板下的岩体看作均质体，得到的是均质体的综合变形参数。在此基础上作了改进，将承压板下的岩体看作双层介质，上部为松动圈，下部为未扰动岩体，基于数值分析和优化设计理论发展了一套分层模量反演方法。将分层反演方法用于研究某水电站坝址区未扰动岩体变形参数，结果表明：分层反演所得岩体变形参数更能反映实际岩体的真实情况，能够有效弥补常规分析方法的不足。

In plate loading test, the deformation properties of rock mass of surface layer will be different from those of inner layer because of occurring disturbance in the surface layer. But, the difference is usually ignored, and the whole rock mass is treated as homogeneous in existing criterion. This unreasonable mode is improved in this article. In a proposed method, the rock foundation is treated as double layers, i.e., the upper layer is disturbed, and the lower layer is undisturbed. Then a back analytic method based on numerical approach and optimizing theory is developed. The new method has been used to study the deformation parameters of undisturbed rock mass in some project, and the applied results? indicate that the deformation parameter of undisturbed rock mass gotten by the proposed method is more reasonable, and can effectively correct the shortage of conventional analyzing method.