The "value" of dense sand, in the context of soil properties often determined by tests like the Standard Penetration Test (SPT), refers primarily to its quantifiable characteristics such as its SPT N-value range and its angle of internal friction (ϕ). According to the provided reference, for dense sandy soil, the SPT N-value ranges from 31 to 50, and the angle of internal friction (ϕ) ranges from 38° to 41°.
Understanding Dense Sand
Sandy soil is classified based on its relative density, which indicates how tightly the sand particles are packed together. Density significantly influences the soil's strength, stiffness, and bearing capacity. Categories typically include Loose, Medium Dense, Dense, and Very Dense. Dense sand, falling between Medium Dense and Very Dense, exhibits moderate to high resistance to penetration and shear.
Key Values for Dense Sand
The provided reference links the classification of sandy soil by relative density to specific ranges of SPT N-values and angles of internal friction. The SPT N-value is the number of blows required to drive a standard sampler a specific distance into the soil, indicating its resistance. The angle of internal friction (ϕ) is a critical parameter in soil mechanics representing the shear strength of granular soil.
Based on the reference, here are the associated values for different relative densities:
| SPT values | Relative Density (or) Consistency | ϕ (°) |
|---|---|---|
| 5 - 10 | Loose | 30 -35° |
| 11 - 30 | Medium Dense | 35 – 38 |
| 31 - 50 | Dense | 38 – 41° |
| > 50 | Very Dense | 41 – 44° |
Specifically for dense sand:
- SPT N-Value: The range is 31 to 50. This higher N-value indicates that dense sand requires significant effort to penetrate, reflecting its compact nature.
- Angle of Internal Friction (ϕ): The range is 38° to 41°. A higher angle of internal friction means the soil has greater shear strength, allowing it to support higher loads and maintain steeper slopes compared to loose sand.
These values are crucial for geotechnical engineers when designing foundations, retaining walls, and other structures built on or with sandy soils. They provide a quantitative measure of the soil's mechanical properties.
