Spider Rock Protection System for Rock Slope Stabilization

C. Joseph, P.E. Bigger

In the proceedings of: GEO2011: 64th Canadian Geotechnical Conference, 14th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, 5th Pan-American Conference on Teaching and Learning of Geotechnical Engineering

Session: Retaining Walls

ABSTRACT: Stabilizing rock formations or blocks has been a combination of engineering and art and common techniques include rock bolts with or without cable lashing and/or nets. The recent development of SPIDER Nets lead to the SPIDER Rock Protection System for stabilizing rock formations. Further, the Ruvolum Rock Dimensioning program was changed for the SPIDER System and it is now a tool for engineers and designers to use. The program is used on-line and it allows the user to analyze sliding and toppling mechanisms. The program is based on Mohr-Coulomb Equilibrium theory and it establishes the relationship between driving and stabilizing forces. The program allows the user to input various site conditions, select anchor spacing and size and the result is an optimized arrangement for the given conditions. As part of the program development, the concept was modeled and tested under laboratory conditions. Field evaluation was completed in 2009 to further verify the program. The program has been successfully used for applications in place in Europe and Asia.

RÉSUMÉ: Formations rocheuses de stabilisation ou de blocs a été une combinaison de l'ingénierie et de l'art et les techniques communes comprennent des boulons d'ancrage, avec ou sans amarrage de câble et / ou des filets. Le développement récent des filets de SPIDER entraîner le système SPIDER Rock protection pour la stabilisation de formations rocheuses. En outre, le Ruvolum Rock Dimensionnement programme a été changé pour le système SPIDER et il est maintenant un outil pour les ingénieurs et les concepteurs à utiliser. Le programme est utilisé en ligne et il permet à l'utilisateur d'analyser les mécanismes de glissement et de renversement. Le programme est basé sur Mohr-Coulomb Théorie de l'équilibre et il établit la relation entre la conduite et la stabilisation de forces. Le programme permet à l'utilisateur des conditions d'entrée différents sites, sélectionnez ancrage espacement et la taille et le résultat est un arrangement optimisé pour les conditions données. Dans le cadre de l'élaboration du programme, le concept a été modélisée et testée en conditions de laboratoire. Evaluation sur le terrain a été achevé en 2009 pour vérifier le programme. Le programme a été utilisé avec succès pour des applications en place en Europe et en Asie. 1 BACKGROUND Over the years, conventional solutions were developed and implemented to hold rock ledges or overhangs or individual loose rocks in place and they included: - Anchor beams - Shotcrete - Cable lashing - Wire rope nets with and without rope restraints The various conventional solutions are outlined in the following paragraphs: 1.1 Anchor beams This method involved the placement of beams with anchors on the slope to hold the rock in place. It often required comprehensive, difficult and intensive construction to place anchor beams directly on the rock slope. The installed anchor beams were highly visibility, subject to weathering and did not enhance the natural scenery of the slope. 1.2 Shotcrete In order to achieve sufficient strength to hold rock in place, anchors are placed in a tight grid along with a rigid wire mesh and whalers. The shotcrete layer needed to have a minimum thickness. The installation of anchors and shotcrete in area with difficult access makes this an expensive solution. Shotcrete is often not very aesthetically pleasing and it can be damaged by water and weather. A newer technique is sculpting the shotcrete which also leads to additional cost. 1.3 Cable lashing The placement of cables to lash rock formations in place were often used but had their limitations. Due to the given geometry of the formation, the placement of the cables was not always ideal and would require over dimensioning. This meant the placement of the anchors for the cables was also not ideal. The cables can only work locally and, over time the rope tension is reduced. 1.4 Wire rope nets with or without cable lashing The use of wire rope nets to cover and hold rock formations was used but had its limitations. The nets were square or rectangular and the nail grid was usually based on net shape. The combination did not

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