---
title: "Wall movement versus earth pressure plot"
subject: "Foundation Engineering"
chapter: 3
key: "semester_5/foundation_engineering:wall-movement-pressure-plot"
source: https://www.bctengineer.com/q/semester_5/foundation_engineering/wall-movement-pressure-plot
site: BCT Engineering
---

# Wall movement versus earth pressure plot

Foundation Engineering · Chapter 3: Lateral Earth Pressure Theories and Retaining Walls

- Asked in: 2078 Bhadra, 2 marks
- Video: [Understanding the soil mechanics of retaining walls](https://www.youtube.com/watch?v=YtQ9ubNbytE) — The Engineering Hub
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/foundation_engineering/wall-movement-pressure-plot
- Whole chapter: https://www.bctengineer.com/md/semester_5/foundation_engineering/chapter-3

## Question

Draw the plot showing the relationship between lateral earth pressure force per unit length of the wall vs. movement of the retaining wall.

## Short answer

At zero movement, lateral force is the at-rest value P0. Moving the wall away from soil by 0.001–0.005 H (sand) reduces force to active minimum Pa; moving it toward soil by 0.01–0.05 H raises it to passive maximum Pp. Pa < P0 < Pp.

## Answer

The plot shows lateral force $P$ on the wall against wall movement $\Delta$ (away from or toward the soil).

```text
  P (force on wall)
  ^
  |                           _______ Pp (passive, maximum)
  |                        .-'
  |                      .'
  |                   .-'
  |              *-'   P0 at rest (zero movement)
  |           .-'
  |  ______.-'
  |  Pa (active, minimum)
  +--------------+------------------------> wall movement
   away from soil 0      toward soil
   (0.001-0.005H)        (0.01-0.05H)
```

- At zero movement the force is $P_0$ (at rest, $K_0$).
- Moving **away** from the soil, the force falls rapidly and reaches the minimum active value $P_a$ after a small movement (0.001-0.005 H in sand).
- Moving **toward** the soil, the force rises and reaches the maximum passive value $P_p$ only after a large movement (0.01-0.05 H in sand; more for clay).
- Order: $P_a < P_0 < P_p$.

## Check yourself

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

1. The order of lateral forces is:
   A. Pp < P0 < Pa
   B. Pa < P0 < Pp
   C. P0 < Pa < Pp
   D. Pa = P0 = Pp
   Answer: B. Moving away gives the minimum Pa; no movement gives P0; moving toward gives the maximum Pp. (Key point: Order of forces)

2. Moving away from the soil, the force:
   A. Rises to Pp
   B. Falls rapidly to Pa after a small movement (0.001-0.005 H in sand)
   C. Stays at P0
   D. Falls only after a large movement
   Answer: B. Active state is reached after a small outward movement. (Key point: Movement for active)

3. Compared to active, the movement to mobilise full Pp is:
   A. Much smaller
   B. The same
   C. Much larger (0.01-0.05 H in sand)
   D. Zero
   Answer: C. Passive needs a large movement toward the soil. (Key point: Movement for passive)

## Related in Foundation Engineering

- [Active pressure on wall, cohesive soil](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Acohesive-wall-pressure-diagram) — Foundation Engineering, chapter 3
- [Braced cut design versus retaining wall](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Abracing-vs-retaining-wall) — Foundation Engineering, chapter 4, asked 2×
- [Earth pressure coefficients and types](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Aearth-pressure-coefficients-types) — Foundation Engineering, chapter 3, asked 2×
- [Active pressure, 8 m wall, table of layers](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Awall-8m-two-layer-table) — Foundation Engineering, chapter 3
- [Passive thrust on retaining wall back](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Awall-passive-thrust-two-layer) — Foundation Engineering, chapter 3
- [Flexible versus rigid retaining structures](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Aflexible-vs-rigid-retaining) — Foundation Engineering, chapter 5, asked 3×

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- [Distribution of lateral force among masonry walls](https://www.bctengineer.com/question.md?key=semester_5%2Fdesign_of_timber_and_masonry_structures%3Alateral-load-sharing-among-piers) — Design of Timber and Masonry Structures, chapter 6
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