Compactibility of soil in landfills primarily depends on which factor?

The compactibility of soil in landfills is significantly influenced by the gradient of the particle size of the soil, which refers to the distribution of different particle sizes present in the soil matrix. A well-graded soil, which has a broad range of particle sizes, can pack more efficiently, leading to higher density and reduced void spaces. This compacting effect is crucial in landfills as it maximizes the volume of refuse that can be accommodated and minimizes settlement over time.

In landfills, achieving optimal compaction is essential to controlling leachate production and minimizing the potential for groundwater contamination. Coarse particles may provide structural stability, while finer particles assist in filling voids and increasing overall density when compacted. Therefore, the gradient of particle size plays a pivotal role in optimizing these factors.

Other factors, such as the moisture content of the soil, do influence compactability but depend on the soil texture and its interaction with different particle sizes. Similarly, while the type of refuse and the point of discharge may affect compaction practices, they are secondary to the inherent properties of the soil itself, particularly the distribution of particle sizes that directly impacts the efficiency of the compaction process.