The uplift resistance Rt combines the footing self-weight and the self-weight of the soil overburden in the shape of a cone as evident from the following figure.
Basis of the cone method
The "Bearing cap." frame in the "Verification on uplift" dialog window serves to input the cone angle α. When calculating the uplift resistance Rt it is also possible to account for the influence of a neighbor foundation either in one or both directions that reduces the volume of the soil cone.
Dialog window "Verification on uplift" - cone method
Influence of a neighbour foundation