As per IS 1498-1970, the particle size of coarse gravel will range within:
80 mm to 20 mm sieve
Particle Size Classification by IS 1498-1970
Soil particles are classified into different categories based on their size. One commonly used standard for this classification in India is IS 1498-1970, which provides guidelines for the classification and identification of soils for engineering purposes.
According to IS 1498-1970, coarse-grained soils are primarily classified into gravel and sand based on particle size. Gravel is further subdivided based on its size range.
Gravel Size Classification
The standard defines the size ranges for different types of gravel:
- Coarse Gravel: Particles ranging from 80 mm to 20 mm.
- Medium Gravel: Particles ranging from 20 mm to 6 mm.
- Fine Gravel: Particles ranging from 6 mm to 4.75 mm.
Particles larger than 80 mm are generally classified as Cobbles (80 mm to 300 mm) or Boulders (>300 mm).
To better understand the classification within IS 1498-1970, consider the following table showing the primary divisions:
| Soil Type | Particle Size Range |
|---|---|
| Boulders | Larger than 300 mm |
| Cobbles | 300 mm to 80 mm |
| Gravel (G) | 80 mm to 4.75 mm |
| Coarse Gravel | 80 mm to 20 mm |
| Medium Gravel | 20 mm to 6 mm |
| Fine Gravel | 6 mm to 4.75 mm |
| Sand (S) | 4.75 mm to 75 microns ($\mu$m) |
| Coarse Sand | 4.75 mm to 2.0 mm |
| Medium Sand | 2.0 mm to 0.425 mm |
| Fine Sand | 0.425 mm to 0.075 mm (75 $\mu$m) |
| Silt and Clay (M&C) | Smaller than 75 microns ($\mu$m) |
Coarse Gravel Range as per IS 1498-1970
Based on the standard IS 1498-1970 classification, the particle size for coarse gravel specifically falls within the range of 80 mm to 20 mm. This range is determined by sieving the soil sample through standard sieves.
Therefore, the correct range for coarse gravel according to IS 1498-1970 is from 80 mm to 20 mm sieve.
Important Questions from Classification of Soils
The Group index value of soil subgrade in pavement construction is 8. The subgrade soil is rated as:
- Uniformity coefficient of a soil is -
The coefficient of curvature for a well graded soil, must be from-
Which soil will take years and decades to undergo full settlement after the new building is constructed?
I.S. Sieve Nos. 10 mm and 4.75 mm are generally used for grading of
