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(so long as "trough subsidence" and not "chimney subsidence" is <br />• maintained). Further, the mine plan on this particular site will <br />not produce subsidence in the toe areas of landslides immediately <br />above the river and, therefore, toe buttresses wi 11 not be <br />"dropped". All subsidence effects will occur within the body <br />area of major slides in lieu of the toe. Nevertheless, within <br />zones that will experience tensile strain and the development of <br />tension cracks, the landslide will initially not know the <br />difference between the unloading associated with the tension <br />crack development and the loss of support from removal of the <br />toe. Durinq this time the potential for initiation of new <br />movement within the slide mass will be very great. This <br />phenomenon will, however, be very short-lived as relatively minor <br />movements will quickly close tension cracks and quickly restore <br />the original state of stress. <br />As movement is initiated, there is always the possibility of the <br />resulting shear strains causing the immobilized shear strength to <br />pass the peak level and approach a residual strength condition. <br />The risk of this phenomenon, however, may be minimized by <br />minimizing insofar as possible the magnitude of tensile ground <br />strain experienced and, therefore, eliminating the extent and <br />size of tension crack development. <br />Yet another short-term effect associated with the development of <br />the tension cracks involves an increase in the avenues available <br />. for the introduction of moisture from surface runoff into the <br />25 <br />