Silt Size Classification according to IS

Introduction:
The Indian Standard (IS) classification system is widely used in civil engineering to classify the size of particles in soils. It categorizes soil particles into different size ranges based on their diameters. Silt is one of the soil types classified by the IS system.

Silt Size Range:
According to the IS classification, the range of silt size particles is from 0.075 mm to 0.002 mm.

Silt Particle Characteristics:
Silt particles are fine-grained soil particles that are intermediate in size between sand and clay. They are smaller than sand particles but larger than clay particles. Silt particles have a smooth texture and can be easily transported by water due to their small size and low settling velocity.

IS Classification System:
The IS classification system divides soil particles into several size ranges, which are labeled as different types of soil. The size ranges are defined based on the diameters of the particles.

Explanation of Options:
Let's go through the given options and see why option D is the correct answer.

a) 4.75 mm to 2.00 mm: This range includes larger particles, which are classified as gravel or sand, not silt.

b) 2.00 mm to 0.425 mm: These particles fall into the sand category according to the IS classification, not silt.

c) 0.425 mm to 0.075 mm: This range includes fine sand particles, not silt.

d) 0.075 mm to 0.002 mm: This range falls within the silt category according to the IS classification system. It includes particles that are smaller than sand but larger than clay.

Conclusion:
According to the IS classification system, the range of silt size particles is from 0.075 mm to 0.002 mm. This range is smaller than sand particles but larger than clay particles. It is important to classify soil particles accurately to understand their behavior and engineering properties.