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Show where ( 23) The change in stress at X - X* o is> AT = T C K - O ( 24) and the total stress at X s X f l is ?•_ 73* ( 25) // For this case, the steepest angle, ft. of " secondary absolute stability" is given by t**( tf)\ ( l- ZM) U^ ( 26) T3. is slightly smaller than fy because the boundaries to which the str- te ss is transferred is larger for the case of the cylinder. In Fig. 8 the angles j\ j JP£ and f. are shown as functions of M for three values of the parameter W . The importance of the " compressibility factor," \/\ , can be observed. During settling and destructive metamorphism, M decreases, consequently, stability increases. However, if the critical layer is near the ground, constructive metamorph ism tends to increase M . As mentioned at the beginning of this section, primary stability is a prerequisite for secondary stability: if the critical curve is reached, a local fracture can only increase the stress at the boundaries, amplify the instability, and cause the fracture to be propagated ad infinitum. 5- STABILITY WITH A CONCENTRATED FORCE ACTING ON THE SURFACE Vertical forces may be applied to a slab by the pass of a skier. The stresses are distributed throughout the snow with a maximum stress approximately below the point of application. As with the original load, the vertical force can be resolved into a tangential and normal component. Assuming that the |
