Kritisk kilteori

Critical taper wedge.svg
Critical taper concept in geodynamics. A wedge of material with density ρ_s is pushed over a slope with angle β with a horizontal line, by a force σ_x (x is the direction parallel to the slope). The wedge makes a slope with a horizontal line with angle α. Forces resisting this push are: 1) the load of an eventual water column above the wedge; 2) the load of the wedge working at the base of the wedge; 3) the shear strength of the base.

• 1) is calculated by multiplying the density of water (ρ_w) with the height of the water column (D), this is multiplied by the sine of angles α and β to get the component parallel to the base angle β.
• 2) is calculated by multiplying the density of the wedge material (ρ_s) with the height of the wedge perpendicular to the base slope (H), this is multiplied by the sine of angle β to get the component parallel to the base angle β.
• 3) is given by the Mohr-Coulomb criterion.

If mechanical equilibrium is assumed the resisting forces are equal to the push, allowing for the calculation of the critical values of α and β when the other parameters are known. Any wedge under mechanical equilibrium will have a certain equilibrium α and β depending on the other parameters. When the angles different from the critical angles, the wedge will reshape itself by internal deformation.