What is critical state concept of soil mechanics?

Abstract. The critical state (or critical void ratio) line is the locus of void ratio-effective stress conditions achieved after shearing a soil to large displacement and after all net void ratio changes and effective stress changes are complete.

What is critical state model?

The “modified Cam-clay theory” is a classical plasticity model. It uses a strain-rate decomposition in which the rate of mechanical deformation of the soil is decomposed into an elastic and a plastic part, an elasticity theory, a yield surface, a flow rule, and a hardening rule.

What are critical state parameters?

The five critical state soil parameters are: λ, slope of the normal compression line (NCL) in the specific volume (υ)—natural logarithm of the mean effective stress ln (p′) plot; κ, slope of the swelling line in the υ − ln (p′) plot; Ν, value of specific volume when p′ = 1 kPa on the normal compression line; Μ, slope …

What is Roscoe surface?

The surface of Roscoe (Hvorslev) is defined as the surface made of the last part of the set of trajectories ending to a given critical point and coming from all states of normally consolidated soils (from all states of over consolidated soils).

What is P and Q in soil mechanics?

The p-q diagram is a method of simplifying the analysis of triaxial and other stress data which are commonly used in soil mechanics. It can be used in a variety of applications and solve a range of problems.

What is critical void ratio?

The critical void ratio is defined as the void ratio at which failure will occur at zero volume change. The concept was first established by Casagrande [1] and following that, a number of methods were suggested for determining this soil characteristic.

What is meant by critical point?

In thermodynamics, a critical point (or critical state) is the end point of a phase equilibrium curve. The most prominent example is the liquid–vapor critical point, the end point of the pressure–temperature curve that designates conditions under which a liquid and its vapor can coexist.

What is the state of sand?

Sand reacts like a solid when you stand on it, and it is more than capable of supporting your weight. Now, if you were to put the same sand particles in an hourglass, these will start flowing through the hole like a liquid.

Is Clay drained or undrained?

Clay behavior depends on the rate of loading (or unloading). When “fast” stress changes take place then clay behavior is typically modeled as “Undrained” while slow stress changes or long term conditions are typically modeled as “Drained”. In the software, the default behavior of a clay type soil is set as “Undrained”.

What is a PQ plot?

How is void ratio calculated?

Divide the weight by the volume (1,000 ml) to find the density of the sand. For example, if the sand weighs 1,500 grams, the density is 1.5. Multiply the voidage by the volume of the dry sand to find the volume of the void. With 1,000 ml of dry sand and a voidage of 0.4, you have a void volume of 400 ml.

When do you use critical state soil mechanics?

CRITICAL STATE SOIL MECHANICS (CSSM) – Is a tool to estimate soil responses when complete characterisation of soil at site is limited (to predict soil’s response from changes in loading during and after construction) – In corporates volume changes in its failure criterion (Mohr coulomb only defines failure as the attainment of the maximum stress.

Why are critical state and elasto plastic soil mechanics criticized?

Critical state and elasto-plastic soil mechanics have been the subject of criticism ever since they were first introduced. The key factor driving the criticism is primarily the implicit assumption that soils are made of isotropic point particles.

How are soil constants related to deviatoric stress?

Thus, {\\displaystyle \\ \\lambda } are soil constants. The first equation determines the magnitude of the deviatoric stress {\\displaystyle \\ p’} . The second equation states that the specific volume {\\displaystyle \\ u } occupied by unit volume of flowing particles will decrease as the logarithm of the mean effective stress increases.

How is the yield surface of Cam clay soil described?

The Original Cam-Clay model is based on the assumption that the soil is isotropic, elasto-plastic, deforms as a continuum, and it is not affected by creep. The yield surface of the Cam clay model is described by the equation.