LEGEND
1 , 2 = Failure planes (2 intersecting joint sets)
3 = Upper ground surface
4 = Slope face
5 = Tension crack
H1 = Slope height referred to plane 1
L = Distance of tension crack from crest, measured along the trace of plane 1.
Swedge > Program Overview
Swedge computes the factor of safety for translational slip of a tetrahedral wedge formed in a rock slope by:
two intersecting discontinuities (joint sets)
the slope face
the upper ground surface
a tension crack (optional).
Typical problem geometry is illustrated below.
Figure 1 – Typical wedge geometry for Swedge analysis [Hoek & Bray (1981)].
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LEGEND 1 , 2 = Failure planes (2 intersecting joint sets) 3 = Upper ground surface 4 = Slope face 5 = Tension crack H1 = Slope height referred to plane 1 L = Distance of tension crack from crest, measured along the trace of plane 1. |
When a pair of discontinuities are selected at random from a set of field data, it is not known whether:
the planes could form a wedge (the line of intersection may plunge too steeply to daylight in the slope face or it may be too flat to intersect the upper ground surface).
one of the planes overlies the other (this affects the calculation of the normal reactions on the plane).
one of the planes lies to the right or the left of the other plane when viewed from the bottom of the slope.
In order to resolve these uncertainties, the solution has been derived in such a way that:
Either of the planes may be labeled 1 (or 2).
Allowance has been made for one of the planes overlying the other (this is illustrated in Figure 2)
The crest can overhang the base of the slope.
Contact may be lost on either plane (this is dependent on wedge geometry, and also on the magnitude of the water pressures acting on the planes).
A check on whether the two planes do form a wedge is included in the solution at an early stage. In addition, Swedge also examines how the tension crack intersects the other planes, accepting only those cases where the tension crack truncates the wedge in a kinematically admissible manner.
Figure 2 – Situation where wedge is formed, and one plane overlies the other
