---
title: "Saturated clay 20 cc numerical"
subject: "Soil Mechanics"
chapter: 2
key: "semester_4/soil_mechanics:saturated-clay-void-ratio-gravity"
source: https://www.bctengineer.com/q/semester_4/soil_mechanics/saturated-clay-void-ratio-gravity
site: BCT Engineering
---

# Saturated clay 20 cc numerical

Soil Mechanics · Chapter 2: Solids- Water –Air Relations and Index properties of soils

- Asked in: 2078 Poush, 4 marks
- Video: [Void ratio, Porosity, Degree of saturation, water content and saturated unit weight](https://www.youtube.com/watch?v=musOA7vzleY) — Civil Engineering
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/soil_mechanics/saturated-clay-void-ratio-gravity
- Whole chapter: https://www.bctengineer.com/md/semester_4/soil_mechanics/chapter-2

## Question

An undisturbed sample of saturated clay has a volume of 20 cc and weighs 38 gm. After oven drying the weight reduces to 28 gm. Calculate the void ratio and specific gravity.

## Short answer

Void ratio e = 1.0, specific gravity G = 2.80.

## Answer

#### Given
$V = 20$ cc, $W = 38$ g, dry weight $W_s = 28$ g, $S = 100\%$.

#### Solution
Weight (and volume) of water: $W_w = 38 - 28 = 10$ g, so $V_w = 10$ cc (taking $\rho_w = 1$ g/cc).

As the clay is saturated, $V_v = V_w = 10$ cc, so:
$$
\begin{aligned}
V_s &= V - V_v = 20 - 10 = 10\ \text{cc} \\
e &= \frac{V_v}{V_s} = \frac{10}{10} = 1.0 \\
G &= \frac{W_s}{V_s\,\rho_w} = \frac{28}{10 \times 1} = 2.80
\end{aligned}
$$

Check: $w = 10/28 = 35.7\%$, and $e = wG = 0.357 \times 2.8 = 1.0$ (agrees).

**Answer: void ratio $e = 1.0$, specific gravity $G = 2.80$.**

## Check yourself

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

1. Volume of water in the sample is:
   A. 28 cc
   B. 10 cc
   C. 38 cc
   D. 20 cc
   Answer: B. Ww = 38 - 28 = 10 g, so Vw = 10 cc. (Key point: Water volume)

2. Because the clay is saturated:
   A. Vv = 0
   B. Va = V
   C. Vs = Vw only if dry
   D. Vv = Vw
   Answer: D. All voids are filled with water, so Vv = Vw = 10 cc. (Key point: Saturation assumption)

3. Void ratio is:
   A. 0.5
   B. 1.0
   C. 2.0
   D. 0.36
   Answer: B. Vs = 20 - 10 = 10 cc, so e = 10/10 = 1.0. (Key point: Void ratio)

4. Specific gravity G is:
   A. 2.00
   B. 1.90
   C. 3.80
   D. 2.80
   Answer: D. G = Ws/(Vs rho_w) = 28/10 = 2.80, checked by e = wG. (Key point: Specific gravity)

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