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DESIGN MANUAL& KEYWALL OPERATING GUIDEINTERNAL STABILITY ANALYSISInternal stability is the ability of the reinforced mass to maintain its structure and resist the applied loadswithout deforming or failing. For a concrete cantilever wall, internal stability is provided by a combinationof the stems bending and shear resistance at the footing and up the stem. In a crib or gabion system, internalstability is the dead weight and ability of each lift to resist sliding and overturning about the layer below.In soil reinforced wall system, it is the tensile and pullout capacity of the reinforcing elements and interunitshear/connection capacity that holds the potential wedge of soil in place. Sliding and shear are alsoevaluated internally to ensure the mass will not fail in internal shear.The retaining wall mass, or structure, is composed of the Keystone units at the face combined withreinforcing elements extending back beyond the Coulomb or Rankine failure plane.The Elements of Internal Design are to ensure:1) The tensile elements do not exceed their working stress or factored resistance limits.2) The tensile elements have adequate connection capacity to the Keystone units.3) The tensile elements have adequate anchorage beyond the potential failure plane to hold thewedge of soil in place.4) There is not a potential surface where the mass can shear internally.5) The facing is stable against potential shear, bulging, and overturning.4.17