ANALYSIS OF GLOBAL STABILITY, ANCHOR SPACING, AND SUPPORT CABLE LOADS IN WIRE MESH AND CABLE NET SLOPE PROTECTION SYSTEMS (05-0851)
Navaratnarajah Sasiharan, Washington State University
Balasingam Muhunthan, Washington State University
Shanzhi Shu, Washington State University
Thomas C. Badger, Washington State Department of Transportation

Wire mesh and cable net slope protection has been in use along North American highways to control rockfall on actively eroding slopes. The basic design of these systems is comparatively similar throughout North America. It consists of a top horizontal cable suspended by regularly spaced anchors, typically a perimeter or widely spaced grid of horizontal and vertical support cables, and double-twisted, hexagonal wire mesh laced to the support ropes. To date, the design of the slope protection system has been based on empirical methods, engineering judgment, and experience. Although these systems generally perform very well, there is some consensus amongst geotechnical specialists that some elements in the system may be over-designed or even unnecessary. In addition, system failures under a variety of loading conditions have occurred within the last several decades, indicating that certain design elements may in fact be under-designed for their desired application. This study presents some analytical and numerical models to evaluate the stability of slope protection systems. The study shows that the inclusion of interior horizontal support ropes in addition to the top horizontal rope do not reduce the stress within the mesh, and accordingly, provides no mechanical benefit. Results also show that the stresses on the vertical support rope are much smaller than the top horizontal support rope. Therefore, the vertical ropes do not need to be as strong as the top horizontal rope. The study also presents some useful design charts for the design of slope protection system.