The shear strength of rockfill has been investigated in the last decade, using the shear test. Unfortunately, much controversy exists concerning stress and strain distribution, strength calculations and failure process within the direct shear test. This testing method has been criticized for non-uniform distribution of stresses and strains for progressive failure within the sample. Besides examining the existing previous experiences, the objective of this study is to investigate the effect of rockfill properties on the shear strength of rockfill under non-uniform stress and strain conditions in the direct shear tests using two dimensional finite element model. This research also aims to illustrate the effect of scale on the shear strength of rockfill by simulating the rockfill response in the conventional and a prototype large direct shear boxes.
La resistance au cisaillement d'enrochement a ete examinee durant la demiere decennie utilisant l'essai de cisaillement, Malheureusement, il existe beaucoup de controverses concernant la distribution d'effort et de deformation, les calculations de la resistsnce et le procede de l'echec au sein de l'essai du cisaillement direct cette methode d'essai a ete critiquee pour la distribution non uniforme des- efforts et deformations pour l'echec -progressif au sein de l'echantillon. Outre l'examen actuel des experiences precedentes, le but de cette etude est de verifier l'effet des proprietes d'enrochement sur la resistance au cisaillement d'enrochement dans les conditions d'effort et de deformation non uniformes dans les essais du cisaillement direct, utilisant un modele d'element fini bidimensionnel. Cette recherche est aussi destinee a montrer l'effet de l'echelle sur la resistance au cisaillement d'enrochement en stimulant la reponse d'enrochement dans la boite de cisaillement conventionnelle et un prototype de boite de cisaillement.
Die scherfestigkeit von Steinschuttmaterial ist in den letzen 10 Jahren neben anderen versuchsmethoden mittels des direkten Scherversuches untersucht worden. Die Zuverlassigkeit dieses versuches ist jedoch umstritten, was die Ergebnisse der Auswertung des Versagensmechanismus und der Scherfestigkeiten betriffi. Dies Iiegt an der ungleichmaβigen Verteilung der Spannungen und Dehnungen und dem progressiven Versagen. Das Ziel der vorliegenden Studie ist es, neben der Analyse der bisher gernachten Erfahrungen die Auswirkungen der Eigenschaften des Steinschuttmaterials auf die Scherfestigkeit bei ungleichmaβigen Spannungs- und Dehnungsverhaltnissen im direkten Scherversuch zu analysieren, wobei die zweidimensionale Finite-Element-Methode angewendet wird. Dabei wird diese Arbeit auch die Maβstabseffekte der Scherfestigkeit des Steinschuttrnaterials durch Simulation des Materialverhalten in herkommlichen Prufbehalten und in Prototypen des "Groβen Rahmenscherversuches" veranschaulichen.
The shear strength of rockfill has been investigated in the last decade, using the shear test. Unfortunately, much controversy exists concerning stress and strain distribution, strength calculations and failure process within the direct shear test. This testing method has been criticized for non-uniform distribution of stresses and strains for progressive failure within the sample. In fact, the major causes of the non-uniform stress conditions are the moment force resulting from the application of load about the shearing plane and the effects of the propagation of peak stress into the interior of the sample. Because the state of stress at the point of failure is unknown, a precise determination of the Mohr-Coulomb failure envelope is not possible. The irregularity of the failure zone is the second argument around the existing mode of failure in the direct shear box testing. It was pointed out that when the peak shear strength was reached, a very irregular failure zone extended across the shearing zone. As the shearing stage continued, the cracks multiplied in a discrete sequence and at diminishing positive angles to the horizontal, forming a continuous zone separating the two halves of the direct shear box.
