Grasselli's 2D morphology parameter ${{\theta }_{\max }^{\ast }/(C+1)}_{2D}$ has been widely used in rock engineering. However, the physical meaning of ${{\theta }_{\max }^{\ast }/(C+1)}_{2D}$ is not clear, and the calculation is complex and time-consuming. By introducing a density function to characterize the distribution of the inclination, this study found that the physical meaning of ${{\theta }_{\max }^{\ast }/(C+1)}_{2D}$ is the expected value of the inclination facing the shear direction. Based on this finding, this study found that ${{\theta }_{\max }^{\ast }/(C+1)}_{2D}$ can be simplified as a statistical parameter. Besides, several new 2D roughness metrics expressed in discrete form were proposed. These new roughness metrics have clear physical meanings and can be obtained easily. This study found that two kinds of weight can be employed to calculate the average inclination facing the shear direction. Besides, this study found several generalized equivalent relationships among some 2D roughness metrics.

Grasselli 的二维形态参数 ${{\theta }_{\mathrm{最大限度}}^{＊}/(C+1)}_{2D}$在岩石工程中得到了广泛的应用。但是，物理意义${{\theta }_{\mathrm{最大限度}}^{＊}/(C+1)}_{2D}$不清楚，计算复杂耗时。本研究通过引入密度函数来表征倾角的分布，发现${{\theta }_{\mathrm{最大限度}}^{＊}/(C+1)}_{2D}$是面向剪切方向的倾角的期望值。基于这一发现，本研究发现，${{\theta }_{\mathrm{最大限度}}^{＊}/(C+1)}_{2D}$可以简化为一个统计参数。此外，还提出了几种以离散形式表示的新 2D 粗糙度度量。这些新的粗糙度指标具有明确的物理意义，并且很容易获得。本研究发现，可以采用两种权重来计算面向剪切方向的平均倾角。此外，本研究还发现了一些二维粗糙度指标之间的几种广义等效关系。