The authors apply the finite element method to simulate the progressive failure phenomenon of rock mass around under-ground structure, and evaluate the effectiveness of tunnel supports constructed in the structure.
In order to demonstate of the effectiveness of this simulation technique, a circular tunnel reinforced by the concrete lining is chosen as an example and the results of numerical calculation are given.
The functions of the support of passive type are said to stiffen the underground strcuture and to reduce the swelling rate of rock wall or to prevent sudden failure of rocks. In order to evaluate the effectiveness of the support of this type quantitatively, we need to find some models which are able to simulate the time dependent deformation of rock materials. Visco-elastic model is the one of these models, and would be effective to analyse the phenomenon in the „soft" rock materials. [1]
In this paper, we give a simulation model which represents the behaviour of rock mass in the process of progressive failure and discuss the effect of support to be required to prevent the sudden collapse of the underground structure.
The rock mass is divided into a number of the element area. A progress of failure in the rock mass is assumed to as the increase of failured elements area, in which the bulk Young's modulus (E), Poisson's number (m) and the effective strength (s) decreases as the fissures develop in the rock material. The change of material constants of the element (g) accompanied with the one step of the progr ess o failure is expressed as
(Equation)
where lower suffix i indicates the number of step in the progressive failure, i. e. the degree of failure.
Let us assume that the tensile strength of the sound rock in vergin state of stress remain constant with time. But when once the stresses in an element of the rock mass increase over the original tensile strength by the effect of excavation, then the element would suffer a damage and some failure or crack might be initiated. Thus, it will be rational to assume that the tensile strength of the element suffered some damages would decrease with time under constant rock pressure.
Pour étudier sur modèle le phenomène de la rupture progressive de la masse rocheuse les auteurs emploient la méthode d’élements finis, et evaluent l’efficacité du cintrage construit dans le tunnel.
Comme un modèle pour la démonstration de cette méthode, on a choisi un tunnel circulaire renforcé par un revêtement en béton, et les résultats du calcul sont présentés.
Um das Verhalten progressiver Brüche des Gebirges in unmittelbarster Nähe von offenen Grubenräumen zu betrachten, wird die Finite-Elemente-Methode angewandt.
Mittels dieser Methode kann die Lastaufnahmefähigkeit der zum Tunnelausbau auszuwertenden Grubenräume errechnet werden.
Als ein Beispiel hierfür wird des Modell eines kreisförmigen mit Betonauskleidung verstärkten Tunnels eingehend betrachtet und die mit Hilfe von Digitalrechnern erzielten Berechnungsergebnisse gezeigt.
