Q1: The shear strength of a soil

ANS:E - all the above.

1. Increases with an increase in the normal stress: This is correct. The shear strength of soil typically increases with an increase in the normal stress acting on it. This relationship is often described by the Mohr-Coulomb failure criterion, which states that the shear strength of soil is directly related to the normal stress acting on a potential failure plane.
2. Is proportional to the cohesion of the soil: This is also correct. Cohesion is one of the components of shear strength in soils, especially in cohesive soils like clays. Cohesion represents the soil's internal strength due to the attractive forces between particles and contributes to its shear resistance.
3. Is generally known as the strength of the soil: While shear strength is a critical component of the overall strength of soil, the term "strength of the soil" encompasses various aspects beyond shear strength, such as compressive strength, tensile strength, and overall stability characteristics.
4. Is proportional to the tangent of the angle of internal friction: This statement is incorrect. The shear strength of soil is not directly proportional to the tangent of the angle of internal friction. However, the angle of internal friction is a fundamental parameter used to characterize the shear strength of granular soils. The relationship between shear strength and the angle of internal friction is described by the Mohr-Coulomb failure criterion, which involves trigonometric functions, but it is not a simple proportionality.