UNIVERSAL PRINCIPLES OF ROCK SLOPE ANALYSIS APPLIED TO EXAMPLES IN THE APPALACHIAN AND SIERRA MOUNTAINS

The Appalachians and the Sierras are worlds apart geologically. The former consists of folded and thrust-faulted sedimentary and metamorphic rocks of Paleozoic age, eroded into valleys and ridges and cut by water gaps. The latter consists of block-faulted granite batholiths of Mesozoic age, carved by streams and sculpted by glaciers. Both experience mass movement wherever slopes are steep. For example, Yosemite National Park in the Sierras of California has experienced more than 519 rock falls and other slope movements since 1857 making it a natural rock fall laboratory. When engineering geologists from Radford University, in the Appalachian Mountains of Virginia, concluded that rock falls from the cliffs of Glacier Point were triggered by wastewater disposal, Yosemite officials quickly dismissed the field evidence and suggested that eastern geologists might not have an adequate understanding of slope processes in the west. Yet analyses of rock slope failures in both settings illustrate that the basic principles transcend the differences in rock type, structure, and age. In these and other environments, water in phreatic zones moves through bedrock along open fractures; rock mass discontinuities can be mapped; water pressure is a function of water height not water volume; and safety factors are ratios between resisting and driving forces. Such universal concepts and more are illustrated in a series of comparative examples from the Appalachian Mountains and the Sierras and are supported by recently released data.