Mechanism separation
Overturning and sliding use different action paths and evidence.
Engineering
Retaining Wall Safety Factor Calculator
Calculate overturning and sliding safety factors for a retaining-wall screening check.
RETAINING WALL SAFETY FACTOR
Keep overturning and sliding checks separate
A wall can pass one mechanism and fail another. Enter the resisting and driving actions for each mode and let the lower factor govern the screening result.
Decision boundary:For geotechnical and structural concept review of separate overturning and sliding ratios; the project standard, drainage, bearing, and global stability still govern.
Overturning factor-
Sliding factor-
Governing factor-
Screen status-
DECISION MAP
Retaining Wall Safety Factor Calculator evidence path
Use the governing mechanism to direct the next design check; do not average the two factors.
| Mode | Resisting action | Driving action | Unit basis | Factor | Screen decision |
|---|
LIVE CALCULATION PROCESS
Formula, symbols, substitution, and final check
FS_OT = M_R / M_O; FS_SL = R_SL / H_D; FS_gov = min(FS_OT, FS_SL)
The two ratios are calculated independently and the smaller one is reported as governing. The 1.5 comparison is only the entered screening threshold in this page.
| Symbol | Meaning | Unit | Current input |
|---|---|---|---|
| MR | Resisting moment about the wall toe | kN*m/m | 820 |
| MO | Driving overturning moment about the toe | kN*m/m | 420 |
| RSL | Available sliding resistance | kN/m | 510 |
| HD | Driving horizontal action | kN/m | 280 |
| FSreq | Entered screening threshold | dimensionless | 1.5 |
HOW TO USE
Keep overturning and sliding checks separate
- Enter resisting and driving actions on the same per-metre wall basis.
- Enter the project screening threshold and identify its governing standard or design note.
- Review overturning and sliding ratios separately; do not average the mechanisms.
- Use the lower factor to select the next geotechnical or structural check.
- Retain drainage, groundwater, load-combination, and wall-geometry evidence with the export.
SUBJECT FUNDAMENTALS
Terms behind Retaining Wall Safety Factor Calculator
- Resisting moment
- Stabilizing moment about toe
- Overturning moment
- Driving moment about toe
- Base resistance
- Available sliding resistance
- Horizontal drive
- Factored lateral demand
- Governing factor
- Lower mechanism factor
CALCULATION METHOD
Why this formula fits the topic
FS_OT = M_R / M_O; FS_SL = R_SL / H_D; FS_gov = min(FS_OT, FS_SL)
The two ratios are calculated independently and the smaller one is reported as governing. The 1.5 comparison is only the entered screening threshold in this page.
DEEPER ANALYSIS
Where professional judgement still matters
Threshold source
The 1.5 screen is not a universal code value; verify the project standard.
Hydraulic effects
Water pressure and drainage can change both driving and resisting actions.
WORKED DECISION CASES
Two realistic uses
Sliding governs the concept review
With 820/420, overturning FS is 1.952; with 510/280, sliding FS is 1.821. The lower sliding factor governs but remains above the entered 1.5 screen.
Drainage assumption changes the screen
Keeping 510 kN/m resistance but increasing horizontal drive to 360 kN/m lowers sliding FS to 1.417. It falls below a 1.5 project screen even if overturning remains above the threshold.
Technical glossary
- Toe
- The reference point about which overturning moments are summed.
- Resisting moment
- The stabilizing moment from weight and other declared actions.
- Sliding resistance
- The available base resistance opposing horizontal movement.
- Driving action
- The factored lateral or overturning demand.
- Safety factor
- Resisting action divided by the matching driving action.
- Drainage
- The water-control assumption that affects wall actions.
EVIDENCE AND DATA LINEAGE
What to retain with the result
Retain load combinations, soil parameters, drainage assumptions, and wall section.
LIMITS AND EXCLUSIONS
What this model does not establish
- No bearing, settlement, seismic, global stability, or water-pressure model is included.
- The screening threshold must be confirmed for the project.
- Use a qualified geotechnical/structural review.
RELIABLE SOURCES
References for method and context
FREQUENTLY ASKED QUESTIONS
Retaining Wall Safety Factor Calculator questions
Why is the lower factor governing?
The least stable mechanism controls a screening decision.
Is 1.5 always required?
No. It is the entered comparison threshold here.
Can I use total wall forces?
Use consistent per-metre actions for the same wall length basis.
Does this include seismic load?
Only if it is already included in the entered driving actions.
What if horizontal drive is zero?
The page rejects zero because a sliding ratio would be undefined.
Does this replace geotechnical design?
No; soil, water, seismic, and code checks remain necessary.
IMPORTANT NOTE
Before relying on the exported result
Preliminary retaining-wall screen only.
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