In *Settle3D,* an excavation is considered to be a negative load.

If you were to model only the excavation, the loading stress would be **-γd** where **d **is the depth of the excavation and **γ** is the unit weight of the soil. The loading stress when modeling only the excavation is the negative of the overburden stress. The total stress would then be **0 kPa** (assuming metric units), since the overburden stress is always added to the loading stress to get the total stress.

If you specify a load of, say, **100 kPa** at the bottom of the excavation, the calculated loading stress will be **100 kPa + excavation load = 100 + (-γd)**. The overburden stress is then added on to make the total stress equal to **100 kPa**. Basically, if you want to model a certain loading stress at the bottom of an excavation, you need to specify a stress equal to the stress from the external load as well as the stress from the overburden.