---
title: "Influence of fault on site selection"
subject: "Engineering Geology I"
chapter: 5
key: "semester_3/engineering_geology_i:influence-of-fault-on-site"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/influence-of-fault-on-site
site: BCT Engineering
---

# Influence of fault on site selection

Engineering Geology I · Chapter 5: Structural Geology

- Asked in: 2063 Baisakh (old course), 2 marks
- Video: [Exam Preparation | Earthquakes, Floods, Landslides, Significance of Faults | Engineering Geology](https://www.youtube.com/watch?v=HCnvZaxs-VU) — CiviL TechnO BrickS
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/influence-of-fault-on-site
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-5

## Question

How does fault influence the site selection criteria?

## Short answer

Active faults can rupture dams and cause leakage; fault zones create weak, crushed rock leading to collapse, water inflow, and sliding. Structures are avoided on fault traces, set back with a setback zone, or founded on treated ground with concrete plugs and grouting.

## Answer

- **Dams and reservoirs**: an active fault can rupture and break the dam; fault zones give leakage paths and weak foundation, so sites on or near a fault are avoided or require major treatment.
- **Tunnels and portals**: crushed fault zones cause roof collapse, squeezing and inflow of water.
- **Slopes and buildings**: faults dipping out of a slope give sliding; buildings should not straddle a fault because of differential settlement and seismic risk.
- **Bridges and roads**: fault displacement can damage piers and alignments.
- **Alternatives**: site should be moved away from the fault trace (a setback zone of tens to hundreds of metres), or the foundation must be excavated and treated by concrete plugs and grouting.

## Check yourself

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

1. Why are sites on a fault avoided for dams?
   A. Faults raise bearing capacity
   B. Faults make water tight
   C. Active faults can rupture and fault zones give leakage and weak foundation
   D. Faults reduce seepage
   Answer: C. Rupture, leakage and weakness. (Key point: Dams)

2. Why should buildings not straddle a fault?
   A. Faults are good for foundations
   B. It saves cost
   C. It reduces water inflow
   D. Differential settlement and seismic risk
   Answer: D. Unequal rock on the two sides. (Key point: Buildings)

3. What is the alternative if a fault cannot be avoided?
   A. Move the site away from the trace or excavate and treat with concrete plugs and grouting
   B. Ignore the fault
   C. Build directly on the fault line
   D. Use shallow footings only
   Answer: A. Setback or treatment. (Key point: Alternatives)

## Related in Engineering Geology I

- [Field identification criteria of fault](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Afield-identification-criteria-of-fault) — Engineering Geology I, chapter 5, asked 7×
- [Field identification criteria of fault and fold](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Afield-identification-criteria-of-fault-and) — Engineering Geology I, chapter 5, asked 2×
- [Methods of surface and subsurface site investigation](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Amethods-of-surface-and-subsurface) — Engineering Geology I, chapter 1, asked 4×

## Related in other subjects

- [Criteria for site selection](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Asite-selection-criteria) — Building Technology, chapter 1
- [Geology in bridge site selection](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Abridge-site-selection) — Engineering Geology II, chapter 4, asked 6×
- [Geology in tunnel site selection](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Atunnel-site-selection) — Engineering Geology II, chapter 4, asked 4×
- [Substation site criteria and H-pole BOQ](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Asubstation-site-boq-h-pole) — Industrial Power Distribution and Illumination, chapter 4