Environmental Engineering Reference
In-Depth Information
FIGURE 6.46
Foliation jointing in the Fordham gneiss (Welfare Island, New York). (At this location the 30-m-deep excavation
encountered high residual stresses.)
Under certain conditions, such as on slopes or other open excavations and in tunnels,
removal of confining material may result in strains and the opening of fractures.
Rupture Strength
Shearing Resistance
As the joints close under applied load, resistance to deformation is developed as the
strength along the joint is mobilized. If the joints are filled with clay, mylonite, or some
other material, the strength will depend on the properties of the fillings. If the joints are
clean, the strength depends on the joint surface irregularities (asperities) as discussed in
Section 3.4.3
(see
Figure 3.45).
