> For the complete documentation index, see [llms.txt](https://docs.enercalc.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.enercalc.com/sel-faq/using-the-software/calculation-modules/retaining-walls/cantilevered-retaining-wall/effects-of-soil-slope.md).

# Effects of Sloping Backfill

How the cantilevered retaining wall module accounts for sloping backfill under EFP, Rankine and Coulomb methods.

## How does the program alter the magnitude of the applied active pressure to account for the sloping backfill?

**EFP:** The program does not alter the magnitude of the applied active pressure to account for the sloping backfill.

**Rankine:** The Rankine equation includes the effects of backfill slope when calculating the active pressure.

**Coulomb:** The Coulomb equation includes the effects of backfill slope when calculating the active pressure.

## What backfill height is used when sloping backfill is specified?

**EFP:** The program uses the height of soil that occurs at the end of the heel.

**Rankine:** The program uses the height of soil that occurs at the end of the heel.

**Coulomb:** The program uses the height of soil that occurs at the end of the heel.

## When is the vertical component typically considered or ignored?

**All:** The user has control over whether the vertical component is applied via the options in the "Use of vertical component of active lateral soil pressure" section of the General tab.

**EFP:** It is generally accepted that an EFP does not produce a vertical component. So it is normal to deselect the options in the "Use of vertical component of active lateral soil pressure" section of the General tab when EFP is applied. When the Soil Slope is Level, the EFP will not result in a vertical component. If the backfill has a non-zero slope, and if user selects any of the options to apply a vertical component, the program uses the Coulomb equation to back-calculate the angle of internal friction using soil slope, soil density and the user-entered equivalent fluid pressure. Then the soil-wall friction angle is assumed to be phi/2.

**Rankine:** The Rankine method states that the active force acts at the same angle as the backfill slope. So it is normal to deselect the options in the "Use of vertical component of active lateral soil pressure" section of the General tab when Rankine method is used in a ***level*** backfill condition. And it is normal to select those options in conditions where Rankine method is used with ***sloping*** backfill.

**Coulomb:** The Coulomb method always prescribes a soil-wall friction force. So it is normal to select those options in conditions whenever Coulomb method is used.

## If there is a vertical component of active force, how is the program treating that component?

**EFP:** The vertical component is applied at the back of the ***stem*** when user selects to include it.

**Rankine:** The vertical component is applied at the back of the heel when user selects to include it.

**Coulomb:** The vertical component is applied at the back of the ***stem*** when user selects to include it.

## Is there anything that the user should be doing manually to adjust the input to account for the sloping backfill?

**EFP:** The user must adjust the magnitude of the EFP.

**Rankine:** No additional action is required on the part of the user.

**Coulomb:** No additional action is required on the part of the user.


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