The design of anchored walls involves a determination of several factors. Included are the size, spacing, and depth of embedment of vertical wall elements and facing; the type, capacity, spacing, depth, inclination, and corrosion protection of anchors; and the structural capacity and stability of the wall, wall foundation, and surrounding soil mass for all intermediate and final stages of construction. The bearing capacity and settlement of vertical wall elements under the action of the vertical component of the anchor forces and other vertical loads must also be evaluated.
AASHTO provides the following guidance:
For walls supported in or through soft clays with Su < 0.3y’H, continuous vertical elements extending well below the exposed base of the wall may be required to prevent heave in front of the wall. Otherwise, the vertical elements are embedded several feet as required for stability or end bearing. (Where significant embedment of the wall is required to prevent bottom heave, the lowest section of wall below the lowest row of anchors must be designed to resist the moment induced by the pressure acting between the lowest row of anchors and the base of the exposed wall, and the force Pb = 0.7(yHBe — 1.4cH — ^cBe) acting at the mid-height of the embedded depth of the wall.)
In the above, the following definitions apply:
Be = width of excavation perpendicular to wall c = cohesion of soil H = design wall height
Su = undrained shear strength of cohesive soil у = soil unit weight y’ = effective unit weight of soil
