Q1: Pick up the incorrect definition from the following:

ANS:D - The water content at which a soil flows, is known plastic limit of the soil

The statement is correct. The water content at which a soil flows is indeed known as the plastic limit of the soil. In soil mechanics, the plastic limit is defined as the water content at which a soil changes from a semisolid state to a plastic state. It is the minimum water content at which the soil can be molded or deformed without crumbling. Below the plastic limit, the soil behaves as a solid, while above it, the soil behaves as a viscous fluid. The plastic limit is determined by conducting a standardized test called the plastic limit test, where soil samples are mixed with water incrementally until they reach a plastic state. At this point, the soil begins to flow along the grooves of a standardized device. The water content corresponding to this flow state is recorded as the plastic limit of the soil. Understanding the plastic limit of a soil sample is important in geotechnical engineering and construction because it helps engineers evaluate the workability and behavior of soils, especially in processes like earthwork, foundation design, and soil stabilization.