---
title: "What is soil mechanics; why study"
subject: "Soil Mechanics"
chapter: 1
key: "semester_4/soil_mechanics:soil-mechanics-why-study"
source: https://www.bctengineer.com/q/semester_4/soil_mechanics/soil-mechanics-why-study
site: BCT Engineering
---

# What is soil mechanics; why study

Soil Mechanics · Chapter 1: Introduction

- Asked in: 2074 Bhadra, 2 marks
- Video: [Introduction to Soil Mechanics | Why Study of Soil Mechanics | Rock Cycle](https://www.youtube.com/watch?v=v6K5N307_ok) — HAMID TheLifeCoach
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/soil_mechanics/soil-mechanics-why-study
- Whole chapter: https://www.bctengineer.com/md/semester_4/soil_mechanics/chapter-1

## Question

What do you understand by soil mechanics and why do you need to study this? What would be a solution of different soil engineering problems?

## Short answer

Soil mechanics applies mechanics and hydraulics to soil behavior. It is studied to design safe foundations, earthworks, and slopes, preventing failures like tilting, piping, and landslides. Solutions include deep foundations, drainage, ground improvement, and retaining structures.

## Answer

**Soil mechanics** is the application of the laws of mechanics and hydraulics to engineering problems involving soil. It deals with the physical properties of soil and its behaviour under stress, deformation and water flow. (Terzaghi called it the "application of mechanics to soils".)

#### Why study it
- All structures transfer their load to the ground, so safe and economical foundations need knowledge of soil strength and settlement.
- Soil is the construction material for dams, embankments and roads.
- Many failures (building tilting, dam piping, landslides) result from lack of understanding of soil.
- It helps choose a suitable foundation type, depth and ground improvement method.

#### Solutions to different soil problems
| Problem | Solution |
|---|---|
| Low bearing capacity | Deeper or wider foundation, piles, stabilisation |
| Large settlement | Preloading, drains, compaction, raft foundation |
| Slope failure | Flatten slope, drainage, retaining structure |
| Seepage and piping | Cut-off, sheet piles, filters |
| Expansive soil | Replacement, lime treatment, deep foundations |
| Liquefaction | Densification, drainage |

## Check yourself

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

1. Soil mechanics is best described as:
   A. The study of rocks only
   B. The application of the laws of mechanics and hydraulics to engineering problems involving soil
   C. The study of concrete behaviour
   D. The design of steel members
   Answer: B. It applies mechanics and hydraulics to soil; Terzaghi called it the application of mechanics to soils. (Key point: Definition)

2. Which is a reason to study soil mechanics?
   A. Soil is irrelevant to dams
   B. It removes the need for site investigation
   C. Failures never relate to soil
   D. All structures transfer load to ground, so safe economical foundations need soil strength and settlement knowledge
   Answer: D. Foundations, dams, embankments and roads all depend on soil behaviour, and many failures result from ignorance of it. (Key point: Why study)

3. A solution for low bearing capacity is:
   A. Filters
   B. Deeper or wider foundation, piles, stabilisation
   C. Preloading with drains only
   D. Flattening the slope
   Answer: B. Increasing foundation size/depth, using piles or stabilising the soil raises capacity. (Key point: Low bearing capacity)

4. For expansive soil the listed solution is:
   A. Drainage only
   B. Cut-off and sheet piles
   C. Densification
   D. Replacement, lime treatment, deep foundations
   Answer: D. Expansive soils are replaced, lime-treated or bypassed with deep foundations. (Key point: Expansive soil)

## Related in Soil Mechanics

- [Define soil; soil engineering problems](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Adefine-soil-engineering-problems) — Soil Mechanics, chapter 1
- [Importance of soil mechanics](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Aimportance-soil-mechanics) — Soil Mechanics, chapter 1, asked 3×
- [Soil mechanics and fluid mechanics](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Asoil-mechanics-fluid-mechanics) — Soil Mechanics, chapter 1
- [Historical development of soil mechanics](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Ahistorical-development-soil-mechanics) — Soil Mechanics, chapter 1
- [Geotechnical problems and their solutions](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Ageotechnical-problems-solutions) — Soil Mechanics, chapter 1, asked 2×
- [Soil classification systems](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Acommon-classification-systems) — Soil Mechanics, chapter 3, asked 3×

## Related in other subjects

- [Scope of applied mechanics in engineering](https://www.bctengineer.com/question.md?key=semester_1%2Fapplied_mechanics%3Ascope-applied-mechanics-engineering) — Applied Mechanics, chapter 1
- [Engineering geological problems of Siwalik zone](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Asiwalik-problems) — Engineering Geology II, chapter 2, asked 4×
- [Engineering geological problems in tectonic divisions](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aengineering-geological-problems-in-tectonic) — Engineering Geology I, chapter 7, asked 2×
- [Case study: problems after implementation](https://www.bctengineer.com/question.md?key=semester_5%2Finstrumentation_ii%3Acs-problems-after-implementing) — Instrumentation II, chapter 10