---
title: "Types of slope failure"
subject: "Soil Mechanics"
chapter: 11
key: "semester_4/soil_mechanics:slope-failure-types"
source: https://www.bctengineer.com/q/semester_4/soil_mechanics/slope-failure-types
site: BCT Engineering
---

# Types of slope failure

Soil Mechanics · Chapter 11: Stability of Slopes

- Asked in: 2073 Magh, 2 marks; 2079 Jestha (asked 2 times)
- Video: [Types of Slope Failure in soil | Elementary Engineering](https://www.youtube.com/watch?v=OBrDbyaHFls) — Elementary Engineering
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/soil_mechanics/slope-failure-types
- Whole chapter: https://www.bctengineer.com/md/semester_4/soil_mechanics/chapter-11

## Question

What are the probable types (basic modes) of failure of slopes? Briefly describe any two with sketch.

## Short answer

Basic slope failure modes are rotational slip (face, toe, base), translational or planar slip, compound slip, wedge failure, infinite slope failure, and flow, fall, or creep. Rotational slip is a circular arc in homogeneous clay; translational slip is a shallow plane slide along a weak layer in cohesionless or infinite slopes.

## Answer

The basic modes of failure of slopes are:

1. **Rotational slip** (slump), which has three sub-types: face, toe and base failure.
2. **Translational slip** (planar), along a shallow plane parallel to the slope.
3. **Compound slip,** with a combined curved and plane surface.
4. **Wedge failure,** sliding of a wedge along weak planes.
5. **Infinite slope (surface) failure,** a shallow slide parallel to a long slope.
6. **Flow, fall and creep** in which soil flows or falls.

#### 1. Rotational slip (circular)

The failure surface is approximately a circular arc, and the soil mass rotates about a centre. It occurs in homogeneous cohesive soils (clay).

- **Toe failure:** the arc passes through the toe; common in steep slopes in soil with a high angle of friction.
- **Face (slope) failure:** the arc ends on the slope above the toe; occurs when a hard layer exists near the toe.
- **Base failure:** the arc goes below the toe into the base; occurs in flat slopes of soft clay with a deep soft layer.

```text
        centre O
          *
        . . .  R
   _____.     .______  <- crest
        \  .'    <- slip circle
         \'
 toe  ----`-------------
  (toe failure: arc passes through the toe)
```

#### 2. Translational slip (planar)

The soil slides along a nearly plane surface, often where a weak layer or a hard stratum lies at shallow depth parallel to the slope. The length is much greater than the depth. It is typical for cohesionless soil and infinite slopes.

```text
  ______
        \\  soil mass
         \\\  -----> slides
          \\\\__ weak plane (parallel to slope)
   ----------------------------
```

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What are the sub-types of rotational slip?
   A. Wedge, fall and flow
   B. Planar, compound and creep
   C. Face, toe and base failure
   D. Infinite, finite and wedge
   Answer: C. Rotational failure depends on where the arc meets the ground. (Key point: Rotational sub-types)

2. When does base failure occur?
   A. In steep slopes of high-friction soil
   B. In flat slopes of soft clay with a deep soft layer
   C. When a hard layer lies near the toe
   D. In dry sand
   Answer: B. The arc goes below the toe through the soft base. (Key point: Base failure)

3. When does toe failure occur?
   A. In steep slopes with a high friction angle, the arc passing through the toe
   B. In flat slopes of soft clay
   C. When a hard layer is near the toe
   D. Only in infinite slopes
   Answer: A. The arc passes through the toe for steeper slopes. (Key point: Toe failure)

4. What characterises translational slip?
   A. Rotation about a centre in homogeneous clay
   B. Flow of liquefied soil
   C. Rotation through a deep arc
   D. Sliding along a shallow plane parallel to the slope, length much greater than depth
   Answer: D. It occurs where a weak layer lies parallel and shallow, typical for cohesionless soils. (Key point: Translational slip)

## Related in Soil Mechanics

- [Causes of slope failure](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Aslope-failure-causes) — Soil Mechanics, chapter 11, asked 4×
- [Slope failure types and prevention](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Aslope-failure-types-prevention) — Soil Mechanics, chapter 11, asked 2×
- [Remedial measures for slope failure](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Aslope-remedial-measures) — Soil Mechanics, chapter 11
- [Finite and infinite slopes](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Afinite-vs-infinite-slope) — Soil Mechanics, chapter 11, asked 2×
- [Infinite dry slope, c = 10 kPa, φ = 25°](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Ainfinite-dry-slope-c10-phi25) — Soil Mechanics, chapter 11
- [Drained and CU tests on two samples](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Adrained-and-cu-two-samples-parameters) — Soil Mechanics, chapter 10

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- [Interaction diagram and failure modes](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Ainteraction-diagram-and-failure-modes) — Design of RCC Structure, chapter 10
- [Modes of failure due to settlement](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Asettlement-modes-sketch) — Foundation Engineering, chapter 6
- [Platen restraint effect and failure modes](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Aplaten-restraint-effect) — Concrete Technology and Masonry Structure, chapter 5