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🪨 Simulink Soil Classification Models

USCS & AASHTO Soil Classification — Powered by MATLAB/Simulink

An educational toolkit for civil engineers and students — classify soils in seconds, straight from Simulink.

📦 Get Started · 📐 Models · 🧪 Example · 🤝 Contributing

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📌 What Is This?

This repository provides two plug-and-play Simulink models that classify soil samples using the two most widely used geotechnical standards:

Model	Standard	Purpose
🟦 USCS	ASTM D2487	Fine-grained soil classification (CH, CL, MH, ML…)
🟧 AASHTO	AASHTO M 145	Highway subgrade suitability (A-1 through A-7-6)

Both models accept the same three laboratory inputs and instantly output a standardized soil group symbol — no coding required.

Who is this for?

• 🎓 Civil engineering students learning soil mechanics
• 🏗️ Geotechnical engineers wanting a fast sanity-check tool
• 🧑‍🏫 Instructors looking for visual, interactive teaching aids

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⚡ Getting Started

Prerequisites

Make sure you have the following installed:

• MATLAB R2023b+
• Simulink (included with most MATLAB licenses)

1 — Clone the Repository

git clone https://github.com/Ahmad-Akram7/Simulink-Soil-Classification.git
cd Simulink-Soil-Classification

2 — Open a Model

Navigate to either model folder and open the .slx file:

USCS_Model/
└── USCS_Soil_Model.slx   ← Open this in Simulink

AASHTO_Model/
└── AASHTO_Soil_Model.slx ← Or this one

3 — Set Your Inputs

On the left side of the model, locate the three Constant input blocks:

Block Name	Description	Typical Range
PercentPassing200	% of soil passing sieve #200	0 – 100
LiquidLimit	Atterberg Liquid Limit (LL)	20 – 100+
PlasticLimit	Atterberg Plastic Limit (PL)	10 – 60+

💡 Tip: Double-click any Constant block to edit its value.

4 — Run & Read Output

Click the ▶ Run button in the Simulink toolbar.
The Display block on the right shows your classification result immediately.

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📐 Models Overview

🟦 USCS Model — USCS_Soil_Model.slx

Standard: ASTM D2487 — Unified Soil Classification System

Classifies fine-grained soils using plasticity characteristics derived from Atterberg limits.

Possible Output Symbols:

Symbol	Soil Type	Description
CH	High-plasticity Clay	Expansive, compressible — poor foundation material
CL	Low-plasticity Clay	Moderate plasticity, common subgrade soil
MH	High-plasticity Silt	Elastic, frost-susceptible
ML	Low-plasticity Silt	Low plasticity, frost-susceptible

Decision Logic (simplified):

IF % Passing #200 ≥ 50 → Fine-Grained Soil
  Plasticity Index (PI) = LL - PL
  IF LL ≥ 50 → High Plasticity (H)
  ELSE       → Low Plasticity (L)

  IF plots ABOVE A-line → Clay (C)
  ELSE                  → Silt (M)

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🟧 AASHTO Model — AASHTO_Soil_Model.slx

Standard: AASHTO M 145 — Classification of Soils and Soil-Aggregate Mixtures

Assesses soil suitability for use as road subgrade material in pavement construction.

Output Groups (A-Scale):

Group	Description	Subgrade Quality
A-1	Stone fragments, gravel, sand	⭐⭐⭐ Excellent
A-2	Silty or clayey gravel/sand	⭐⭐⭐ Good
A-3	Fine sand	⭐⭐ Good
A-4	Silty soil	⭐⭐ Fair
A-5	Silty soil (elastic)	⭐ Poor
A-6	Clayey soil	⭐ Poor
A-7-5	Clayey soil (elastic)	⭐ Poor
A-7-6	Clayey soil (expansive)	⭐ Very Poor

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🧪 Example Run

Here's a complete worked example using a high-plasticity clay sample:

Inputs

Percent Passing #200 Sieve:  60%
Liquid Limit (LL):           55
Plastic Limit (PL):          28
Plasticity Index (PI):       27   # Computed: LL - PL

Results

🟦 USCS Output CH (High-Plasticity Clay) LL = 55 > 50 → High plasticity PI = 27 → Plots above A-line → Clay

🟧 AASHTO Output A-7-6 (Expansive Clayey Soil) High fines + high LL + high PI → Poorest subgrade category

✅ Both models correctly identify this as a high-plasticity clay — a soil type that engineers must treat carefully due to its shrink-swell behavior and low bearing capacity.

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🗂️ Repository Structure

Simulink-Soil-Classification/
│
├── 📁 USCS_Model/
│   └── USCS_Soil_Model.slx          # USCS Simulink model
│
├── 📁 AASHTO_Model/
│   └── AASHTO_Soil_Model.slx        # AASHTO Simulink model
│
├── 📁 Report/
│   ├── USCS MODEL.png               # USCS model screenshot
│   └── AASHTO MODEL.png             # AASHTO model screenshot
│
├── LICENSE                          # MIT License
└── README.md                        # This file

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🔑 Key Concepts Glossary

Term	Definition
Sieve #200	0.075 mm opening — separates fine from coarse-grained soils
Liquid Limit (LL)	Water content at which soil transitions from plastic to liquid state
Plastic Limit (PL)	Water content below which soil behaves as a semi-solid
Plasticity Index (PI)	PI = LL − PL; measures the range of plastic behavior
A-line	Boundary on the Casagrande plasticity chart separating clays (C) from silts (M)
USCS	Unified Soil Classification System — general geotechnical use
AASHTO	American Association of State Highway and Transportation Officials standard

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🤝 Contributing

Contributions are warmly welcomed! Here's how to get involved:

1. Fork the repository
2. Create a feature branch: git checkout -b feature/coarse-grained-uscs
3. Commit your changes: git commit -m 'Add coarse-grained soil classification'
4. Push to the branch: git push origin feature/coarse-grained-uscs
5. Open a Pull Request

💡 Ideas for Contributions

• Add coarse-grained USCS classification (GW, GP, SW, SP…)
• Extend AASHTO to include Group Index (GI) calculation
• Add a MATLAB Live Script companion for step-by-step walkthroughs
• Create a standalone App Designer GUI for non-Simulink users
• Add input validation blocks for out-of-range values

Please open an issue first for major changes so we can discuss the approach.

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📄 License

This project is released under the MIT License — free to use, modify, and distribute.
See the LICENSE file for full details.

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Built for engineers, by engineers.
If this saved you time, consider ⭐ starring the repo!

Made with ☕ and a deep appreciation for geotechnical engineering