FE Civil Practice Question Solution included after investigation
CASE E-101 · FE

The Soil Sample With e = 0.80, Not 0.50

Using wet density as dry density produced e=0.50. Correcting for 20% water content gave e=0.80 and 67.5% saturation.

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Case E-101 engineering failure visual
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Follow the investigation process used in the field — in five guided steps.

1

Inspect

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2

Commit

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3

Prove

Run calculations and test your idea.

4

Fix

Select and validate a safe correction.

5

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Case Brief

SAME PRINCIPLES. HIGHER STANDARDS.
PROBLEM STATEMENT

A soil specimen has total volume 0.050 m³, total mass 90 kg, water content w=20%, and specific gravity Gs=2.70. Take rho_w=1000 kg/m³. Determine dry density, void ratio, and degree of saturation.

Geotechnical Engineering Civil Design Verification Root Cause Analysis Safe Correction
E-101
INVESTIGATION WORKSPACE WORK THROUGH THE CASE — YOUR CHOICES MATTER.
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CASE CLOSED · ENGINEERING VERDICT

What actually failed — and what should change.

What failed

Wet density replaced dry density.

What was missed

Water content is defined relative to dry solids mass.

Corrected model

Find dry mass first, then use dry density in soil phase relations.

QUICK ANSWER

Ms=90/1.20=75 kg and rho_d=75/0.05=1500 kg/m³. Thus e=2.70(1000)/1500-1=0.80, and S=0.20(2.70)/0.80=67.5%.

ENGINEERING TAKEAWAY

First remove water mass using w=Mw/Ms, then use dry density in the phase-relation equations.

CASE QUESTIONS

Questions this case should settle.

Which density is used to calculate soil void ratio from specific gravity?

Dry density.

NEXT FE PRACTICE QUESTION

The Footing That Held 614 kPa, Not 331

Geotechnical Engineering · 5–10 min

Continue Practice →
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Real failures. Lasting skills.

Each case is designed to build the judgment, analysis, and confidence you need for engineering exams — and beyond.

  • Apply core engineering concepts to real-world problems
  • Practice structured troubleshooting and analysis
  • Strengthen exam-ready thinking through realistic scenarios
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The sealed debrief unlocks with the root cause, corrected reasoning, fix, and takeaway.