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Hello,

Relative density is described on this page of the documentation. To summarize, it's represented by a percentile because it's a ratio that represents how loose or compact the soil is. Soil with 100% initial relative density has the smallest amount possible of voids in it (eg, pockets of air) and so it behaves as though it is as tightly compacted as possible. On the contrary, 0% initial relative density would begin the simulation as loose as possible. The math is described in more detail in the following locations (external links):

- https://theconstructor.org/geotechnical/determination-relative-density-soil/34777/
- https://www.eurocode.us/soil-mechanics/e.html

The Soil Materials extension allows you to select from a list of Soil Material Presets. For example, clay or sand. It's described on this page.

Regards,

--Oliver

## shinya katsuma

Hi.

I'm using Vortex Studio to simulate excavation.

I've already realized that I can change the hardness of soil by changing initial relative density in earthwork zone.

However, I'm not sure what initial relative density exactly mean especially in the context of soil mechanics.

In concrete, I don't know why the unit of initial relative density is "%", not g/m^3 or something like that.

Could you clarify this point?

Vortex Studio Supportsaid 2 months agoHello,

Relative density is described on this page of the documentation. To summarize, it's represented by a percentile because it's a ratio that represents how loose or compact the soil is. Soil with 100% initial relative density has the smallest amount possible of voids in it (eg, pockets of air) and so it behaves as though it is as tightly compacted as possible. On the contrary, 0% initial relative density would begin the simulation as loose as possible. The math is described in more detail in the following locations (external links):

- https://theconstructor.org/geotechnical/determination-relative-density-soil/34777/

- https://www.eurocode.us/soil-mechanics/e.html

The behaviour of the soil can be further defined by the Earthwork Zone's inputs "Shear Strength" and "Flow Velocity Scale" (these are described on this page) and in the Soil Materials extension.The Soil Materials extension allows you to select from a list of Soil Material Presets. For example, clay or sand. It's described on this page.

Regards,

--Oliver