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Theory of failure, was first proposed by ____________
Coulomb
Mohr
Casagrande
Darcy
Coulomb
Charles-Augustin de Coulomb first proposed the empirical failure criterion for soils in 1776. This theory establishes that the shear strength of a soil is a linear function of the normal stress acting on the failure plane.
Charles-Augustin de Coulomb first proposed the empirical failure criterion for soils in 1776. This theory establishes that the shear strength of a soil is a linear function of the normal stress acting on the failure plane.
╧ДfтАЛ=c+╧Гtan(╧Х) тАФ Coulomb's shear strength equation where ╧ДfтАЛ is the shear strength, c is cohesion, ╧Г is normal stress, and ╧Х is the angle of internal friction.
The principle assumes that failure occurs when the shear stress on a plane reaches a critical limit defined by internal friction and cohesion. As normal stress increases, the frictional resistance between soil particles increases proportionally, leading to a higher shear strength limit.
Coulomb's law is the foundation of soil shear strength analysis.
It assumes a linear relationship between shear stress and normal stress at failure.
The criterion is strictly valid for drained conditions in many soil types.
Mohr later generalized this for a 3D stress state (Mohr-Coulomb criterion).
Simple mathematical model for shear strength.
Widely applicable for basic geotechnical design (e.g., retaining walls, foundations).
Fails to account for the curved nature of failure envelopes in some soils at high pressures.
Does not inherently account for pore water pressure (needs Effective Stress principle).
Bearing capacity of foundations.
Earth pressure calculations for retaining walls.
Slope stability analysis.
Option B (Mohr) expanded Coulomb's concept into the Mohr-Coulomb failure criterion for multi-axial stress states.
Option C (Casagrande) is famous for the Unified Soil Classification System and critical state soil mechanics.
Option D (Darcy) is renowned for his work on fluid flow through porous media (Darcy's Law).
A is correct тАФ Coulomb was the first to propose the fundamental linear relationship between shear strength and normal stress in soils.
Always remember the difference between Coulomb's law (original 2D linear model) and the Mohr-Coulomb criterion (3D extension). In exams, if the question asks for the 'first' proposed, it is always Coulomb.