1.2.2. Procedure

1. About 3 kg of dry soil, with all lumps pulverized and passing through 4.75 mm sieve is taken.
2. The quantity of water to be added in the first trial is decided. (Less for coarse grained soil and more for fine grained soil).

The procedure begins with preparing the soil sample. A specific amount of dry soil, approximately 3 kg, is needed. This soil must be free of lumps and should pass through a sieve with 4.75 mm openings to ensure it is uniform. Then, you determine how much water to add, based on the type of soil. Coarse-grained soil, like sand, requires less water compared to fine-grained soil, like clay, which needs more water for proper compaction.

Think about baking a cake. If you want a light and fluffy cake (like coarse-grained soil), you wouldn’t add too much liquid. But if you were making a dense pudding (like fine-grained soil), you would need more liquid to get the right consistency.

3. Mould without base plate & collar is weighed.
4. The inner surfaces of mould, base plate and collar are greased.

Once the soil sample is ready, the next step involves preparing the mould. The mould, which is a cylindrical container designed for compacting the soil, must be weighed to know its initial mass before adding the soil. After weighing, the inner surfaces of the mould, plate, and collar are greased to prevent the soil from sticking to the sides, which ensures smoother removal after compaction.

Imagine using a cookie cutter to shape dough. Just as you would grease the cutter to stop the dough from sticking, greasing the mould helps the compacted soil easily come out without breaking.

5. Water and soil are thoroughly mixed.
6. Soil is placed in mould and compacted in three uniform layers, with 25 blows in each layer. Blows are maintained uniform and vertical and height of drop is controlled.

Next, the greased mould is filled with the properly mixed soil and water. The soil is compacted in three layers, where each layer undergoes 25 blows from the rammer. It is crucial that the blows are uniform and vertical, and the rammer should drop from a consistent height to ensure the soil is compacted evenly across all layers.

Consider packing a suitcase. You can’t just pile clothes haphazardly; instead, you would layer them neatly and press down evenly to fit everything in, much like how soil is compacted in layers to maximize density.

7. After each layer, top surface is scratched to maintain integrity between layers.
8. The height of top layer is so controlled that after compaction, soil slightly protrudes into collar.
9. Excess soil is scraped.

After compacting each layer, the surface is scratched to help bond with the next layer, preventing separation. The top layer's height is adjusted so that when fully compacted, it slightly presses against the collar of the mould. This ensures optimal density. Any excess soil is then removed to keep the final sample neat and uniform.

Think of stacking books; if the top book isn't aligned properly, it could slide off. Scratching the layers helps them stick better together, just like making sure each book has a solid foundation to rest on.

10. Mould and soil are weighed (W).
11. A representative sample from the middle is kept for the determination of water content.
12. The procedure is repeated with increasing water content.

Once the soil has been compacted, the next step is to weigh the mould with the compacted soil to get a measurement denoted as W. A sample is taken from the middle of the compacted soil, which will be used to find out its moisture content. This entire process is repeated with different amounts of water added to analyze how varying moisture affects the soil's density and compaction.

It’s like checking the density of a sponge after soaking it with different amounts of water. By weighing the sponge each time, you see how the absorbed water changes its overall mass.

13. The number of trials shall be at least 6 with a few after the decreasing trend of bulk density.

To ensure accuracy in the results, the process should be repeated at least six times, each time adjusting the water content. This helps observe the trend in bulk density, particularly if it begins to decrease, indicating a saturation point for the soil's compaction.

Think of testing a new recipe. You might make it multiple times, tweaking the ingredients slightly each time to see what gives the best taste and texture. Similarly, these trials help find the ideal moisture content for soil compaction.

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