The assumed mode of failure for shotcrete is punching shear. The area the wedge has to punch through (shear) is given by the product of the perimeter of the exposed face and the thickness (t) of shotcrete (see figure below). The shotcrete acts in a direction normal to the excavation wall that it is supporting. For a flat exposed face the shotcrete capacity is given by:
where is the shear
strength of the shotcrete. For a wedge with a non-flat exposed face
(piece-wise linear) the capacities of each segment are added vectorially
and the shotcrete acts in the direction of the resultant vector. The resultant
shotcrete support force is always included as a Passive
force in the Unwedge analysis.
Shotcrete Applied to Wedge