Preferred Soil for Central Impervious Core of a Zoned Embankment Earthen Dam

The central impervious core of a zoned embankment type of an earthen dam plays a crucial role in preventing seepage and leakage of water through the dam. The most preferred soil for this core is clay mixed with fine sand. Let's understand why.

Properties of Ideal Soil for Impervious Core

The ideal soil for the central impervious core of a zoned embankment earthen dam should have the following properties:

1. High Plasticity: The soil should have high plasticity to prevent any cracks or fissures from forming in the core.

2. Low Permeability: The soil should have low permeability to prevent water from seeping through the core.

3. High Cohesion: The soil should have high cohesion to provide stability to the core.

4. High Compaction: The soil should be able to achieve high compaction to form a dense and stable core.

Why Clay Mixed with Fine Sand is Preferred?

Clay mixed with fine sand is the most preferred soil for the central impervious core of a zoned embankment earthen dam because it possesses all the above properties. Let's understand how:

1. High Plasticity: Clay has high plasticity, which prevents any cracks or fissures from forming in the core. Fine sand helps in reducing the plasticity index of the clay, making it easier to work with.

2. Low Permeability: Clay has low permeability, which prevents water from seeping through the core. Fine sand helps in reducing the hydraulic gradient of the soil, which further reduces the permeability.

3. High Cohesion: Clay has high cohesion, which provides stability to the core. Fine sand helps in increasing the angle of internal friction of the soil, which further enhances the stability.

4. High Compaction: Clay mixed with fine sand can achieve high compaction to form a dense and stable core. The compaction can be achieved through proper moisture content, compaction energy, and compaction method.

Conclusion

In conclusion, clay mixed with fine sand is the most preferred soil for the central impervious core of a zoned embankment earthen dam because it possesses the required properties of high plasticity, low permeability, high cohesion, and high compaction.

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