The initial or frozen-in double refraction is replaced by an equivalent or virtual state of stress. 初双折射或被冻结的双折射，可用一个等效或有效应力状态来代替。
Seismic responses of unconsolidated sands indicate that Poisson's ratio is related to the parameters of sand with low effective stress. 非固结砂岩的地震响应研究表明泊松比参数与低有效应力的砂岩模型参数有关。
