Modified Anisotropic Linear Model 4 (ALM4) is the fourth generation of the Anisotropic Linear Model. It is a material strength model for anisotropic rock mass conditions. The strength model requires input parameters such as orientation of the weakness plane, normal stress, along with cohesions and friction angles for both the weakness plane and the rock mass. When first developed by Snowden Mining Industry Consultants in 2005, it assumed a linear relationship, both upslope and downslope between shear strength and the orientation in the rock mass. This orientation in the rock mass is known as the Angle of Anisotropy, which is measured as the orientation of an arbitrary slice relative to the orientation of the bedding plane (usually the weakness plane). As the ALM strength model evolved, the fourth generation ALM4 now has differences from its predecessors. Most notably, it now includes defined equations to represent the relationship between the Angle of Anisotropy and the shear strength at any orientation. Simply put, this advancement allows the user to determine shear strength at any orientation in the rock mass.
ALM4 presents other significant information, such as shear strength differentials in the upslope and downslope directions; percentages of shear strength differential; and relationships between the Angle of Anisotropy and the percentage of shear strength differential. ALM4 accommodates simple input parameters to provide valuable modeling information in anisotropic environments.
The latest version of SVSLOPE® features implementations of ALM1, 2, 3 and 4.