---
title: "Modes of failure due to settlement"
subject: "Foundation Engineering"
chapter: 6
key: "semester_5/foundation_engineering:settlement-modes-sketch"
source: https://www.bctengineer.com/q/semester_5/foundation_engineering/settlement-modes-sketch
site: BCT Engineering
---

# Modes of failure due to settlement

Foundation Engineering · Chapter 6: Bearing Capacity and Settlement of Shallow Foundations

- Asked in: 2076 Chaitra, 5 marks
- Video: [Foundation Engineering | Modes of failure of structure | Shear criteria and settlement criteria](https://www.youtube.com/watch?v=kDG7El6ONSA) — Digitech education
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/foundation_engineering/settlement-modes-sketch
- Whole chapter: https://www.bctengineer.com/md/semester_5/foundation_engineering/chapter-6

## Question

Describe the different modes of failure due to the settlement with neat sketches.

## Short answer

Uniform settlement causes no distortion but may affect services. Tilting occurs from eccentric loads and endangers tall structures. Differential settlement causes angular distortion, leading to sagging or hogging and cracking; allowable differential settlement is about 1/300 to 1/500 of span.

## Answer

Settlement of a structure can take three forms, depending on how the footings settle relative to each other.

#### 1. Uniform (total) settlement
All footings settle by the same amount. The structure moves down without distortion and there is little damage. It affects only the connections to services and the level of the building.

```text
 Before:  |======|      After:  |======|
          ########             ########
                               (all down)
```

#### 2. Tilting (rotation)
One side settles more than the other, so the building rotates as a rigid body. It occurs with eccentric loads, non-uniform soil, or adjacent heavy loads. Tall structures such as chimneys and towers are most affected, and the Leaning Tower of Pisa is an example.

```text
     /|
    / |  <- tilted rigid body
   /__|
  ######
```

#### 3. Differential settlement
Different footings settle by different amounts, giving **angular distortion** $\delta/L$ between points. It distorts the frame and causes cracks and damage to beams, walls and floors. Two shapes are common:
- **Sagging (dishing):** the centre settles more than the ends. Cracks appear in the lower part of the wall.
- **Hogging:** the ends settle more than the centre. Cracks appear in the upper part.

```text
 Sagging (centre down)              Hogging (centre up)

 ========            ========               ________
         \          /                      /        \
          \________/             =========/          \=========
```

The differential settlement is limited to about 1/300 to 1/500 of the span to avoid cracking (about 20 mm for footings in sand and 40 mm in clay).

## Check yourself

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

1. What is the main effect of uniform settlement?
   A. Severe cracking
   B. Tilting
   C. Hogging cracks
   D. Little damage, mostly affecting service connections and level
   Answer: D. All footings move equally so there is no distortion. (Key point: Uniform settlement)

2. What is tilting?
   A. Rigid-body rotation as one side settles more
   B. Equal settlement of all footings
   C. Centre settling more than ends
   D. Cracking of beams only
   Answer: A. Occurs with eccentric loads or non-uniform soil. (Key point: Tilting)

3. Which describes sagging (dishing)?
   A. Ends settle more, cracks in the upper part
   B. Centre settles more than the ends, with cracks in the lower part of the wall
   C. All settle equally
   D. Rigid rotation
   Answer: B. Hogging is the opposite. (Key point: Sagging)

4. What is the measure of differential settlement damage?
   A. Total settlement only
   B. Settlement/width ratio of 1
   C. Angular distortion delta/L, limited to about 1/300 to 1/500
   D. Pore pressure
   Answer: C. Limiting delta/L avoids cracking. (Key point: Angular distortion)

## Related in Foundation Engineering

- [General, local and punching shear failure](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Amodes-shear-failure) — Foundation Engineering, chapter 6, asked 4×

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