---
title: "ISSCS classification, 55% passing 200"
subject: "Soil Mechanics"
chapter: 3
key: "semester_4/soil_mechanics:issc-classify-passing-55"
source: https://www.bctengineer.com/q/semester_4/soil_mechanics/issc-classify-passing-55
site: BCT Engineering
---

# ISSCS classification, 55% passing 200

Soil Mechanics · Chapter 3: Soil Identifications and Classification

- Asked in: 2075 Baisakh, 6 marks
- Video: [Numericals on Soil Classification | Gate 2021 |](https://www.youtube.com/watch?v=bsIaC09YaGo) — TechnoCivil
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/soil_mechanics/issc-classify-passing-55
- Whole chapter: https://www.bctengineer.com/md/semester_4/soil_mechanics/chapter-3

## Question

A soil has the following characteristics:
a) Percentage of soil passing No. 200 sieve = 55
b) Percentage of coarse fraction passing No. 4 sieve = 60
c) Liquid limit = 68%
d) Plastic limit = 22%
Classify the given soil according to ISSCS.

## Short answer

CH, inorganic clay of high plasticity (fat clay). Fine-grained because 55% passes No. 200; wL=68>50 gives high plasticity. Ip=46 exceeds A-line value 35, so clay.

## Answer

#### Given
Passing No. 200 $= 55\%$; $w_L = 68\%$; $w_P = 22\%$ (the percentage of coarse fraction passing No. 4 is not needed).

$$
I_p = 68 - 22 = 46\%
$$

#### Step 1: Coarse or fine?
Since 55% passes the 75 micron sieve (more than 50%), the soil is **fine-grained**.

#### Step 2: Plasticity group (IS 1498)
- $w_L < 35\%$: low (L); $35 - 50\%$: medium (I); $> 50\%$: high (H).
- $w_L = 68\% > 50\%$: **high plasticity (H)**.

#### Step 3: Position relative to the A-line
$$
I_{p,A\text{-line}} = 0.73(w_L - 20) = 0.73(68 - 20) = 35.0\%
$$
$I_p = 46 > 35.0$: the soil plots **above the A-line**, so it is a **clay (C)** (inorganic).

**Answer: CH, inorganic clay of high plasticity (fat clay).** Because 45% is coarse, it may be described as a sandy or gravelly clay.

## Check yourself

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

1. Ip is
   A. 22%
   B. 46%
   C. 90%
   D. 68%
   Answer: B. Ip = wL - wP = 68 - 22. (Key point: Plastic index)

2. wL = 68% in the IS system is
   A. low (L)
   B. medium (I)
   C. high plasticity (H)
   D. organic (O)
   Answer: C. wL > 50% is H. (Key point: Plasticity group)

3. A-line Ip at wL = 68 is
   A. 35.0%
   B. 46%
   C. 48%
   D. 21%
   Answer: A. 0.73 x 48 = 35.0. (Key point: A-line)

4. Result: Ip = 46 > 35, wL > 50 gives
   A. MH
   B. CI
   C. OH
   D. CH
   Answer: D. Above the A-line is clay; high plasticity. (Key point: Symbol)

## Related in Soil Mechanics

- [Classify soil, No. 4 70%, No. 200 30%](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Aclassify-soil-no4-no200-ll33) — Soil Mechanics, chapter 3
- [USCS classification, coarse fraction 62%](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Auscs-classify-coarse-fraction-62) — Soil Mechanics, chapter 3
- [AASHTO classification of inorganic soil](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Aaashto-classify-inorganic-soil) — Soil Mechanics, chapter 3
- [USCS classification using D10, D30, D60](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Auscs-classify-d-values) — Soil Mechanics, chapter 3
- [USCS classification, 75 micron 62%](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Auscs-classify-75micron-62-percent) — Soil Mechanics, chapter 3
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