Determination of the water content of coarse grain soil is done by Pycnometer

Introduction:
The water content of soil is an important parameter in geotechnical engineering as it affects the behavior and properties of soil. Coarse grain soil refers to soil with larger particle sizes, such as gravel or sand. Determining the water content of coarse grain soil is essential for various engineering calculations and design considerations.

Pycnometer Method:
The pycnometer method is commonly used to determine the water content of coarse grain soil. This method involves measuring the mass of the soil sample before and after drying, and then calculating the water content based on the difference in mass.

Procedure:
The following steps are typically followed in the pycnometer method for determining the water content of coarse grain soil:

1. Sample Preparation:
- Collect a representative soil sample from the field.
- Remove any organic material or debris from the sample.
- Break down large particles to ensure uniformity.

2. Weighing the Pycnometer:
- Clean and dry the pycnometer thoroughly.
- Weigh the empty pycnometer accurately.

3. Soil Sample Preparation:
- Take a known mass of the soil sample (typically around 100 grams).
- Place the soil sample in a container and add distilled water.
- Mix the soil and water thoroughly to ensure complete saturation.

4. Filling the Pycnometer:
- Transfer the saturated soil sample into the pycnometer.
- Fill the pycnometer completely, ensuring no air gaps.

5. Weighing the Filled Pycnometer:
- Weigh the pycnometer with the soil sample accurately.

6. Drying the Soil Sample:
- Place the filled pycnometer in an oven at a specified temperature (e.g., 105°C) for a specific duration (e.g., 24 hours).
- Remove the pycnometer from the oven and let it cool to room temperature.

7. Weighing the Dried Pycnometer:
- Weigh the pycnometer with the dried soil sample accurately.

Calculation:
The water content of the coarse grain soil can be calculated using the following equation:

Water content (%) = [(Mass of water / Mass of dry soil)] × 100

Where:
- Mass of water = Mass of filled pycnometer - Mass of dried pycnometer
- Mass of dry soil = Mass of dried pycnometer - Mass of empty pycnometer

Conclusion:
The pycnometer method is a reliable and widely used technique for determining the water content of coarse grain soil. By accurately measuring the mass of the soil sample before and after drying, the water content can be calculated, providing valuable information for geotechnical engineering projects.