What Is Mohr's Circle? The Purpose Of Mohr's Circle

The shear strength of soil is generally characterized by the Mohr–Coulomb failure criterion. This criterion states that there is a linear relationship between the shear strength on the failure plane at failure (τff) and the normal stress on the failure plane at failure (σff) as given in the following equation:
                            τff = σff tanφ + c
where φ is the friction angle and c is the intrinsic cohesion. The strength parameters (φ, c) are used directly in many stability calculations, including bearing capacity of shallow footings, slope stability, and stability of retaining walls. The line defined by Eq. (17.1) is called the failure envelope.

A Mohr’s circle tangent to a point on the failure envelope (σff, τff) intersects the x-axis at the major and minor principal stresses at failure (σ1f, σ3f). For many soils, the failure envelope is actually slightly concave down rather than a straight line.

For a comprehensive review of Mohr’s circles and the Mohr–Coulomb failure criterion, see Lambe and Whitman [1969] and Holtz and Kovacs [1981]. But more online resource, below are links to articles that best explain and gives example on the application of Mohr's Circle:

Mohr's Circle Calculator
Given the stress components sx, sy, and txy, this calculator computes the principal stresses s1, s2, the principal angle qp, the maximum shear stress tmax and its angle qs. It also draws an approximate Mohr's cirlce for the given stress state. Continue reading...

Mohr's Circle for 2-D and 3-D Stress Analysis
After the data for the Mohr's circle are input, press the button "Draw", then the Mohr's circle can be created; press the button "fill", the Mohr's circle are created and filled with red color. If the Mohr's circles are too small, press the button "size 1" or "size 2" to enlarge them. Whenever the data for the Mohr's circle are modified, press "Draw" or "fill" button to get modified Mohr's circle. Besides, the paramters for the Mohr's circle and calculated principal stresses and maximum shear stress are given too. Continue reading...

Mohr's Circle Information
Mohr's circle, named after Christian Otto Mohr, is a two-dimensional graphical representation of the state of stress at a point. The abscissa, , and ordinate, , of each point on the circle are the normal stress and shear stress components, respectively, acting on a particular cut plane with a unit vector  with components. Continue reading...

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