The behaviors and stress distributions of the inclined jointed rock masses with different dip angles obtained from DDA are compared to the results of laboratory tests. By calculating the block stress distributions, it is confirmed that DDA can reproduce the arching around the trap door when lowering the trap door. The shapes of arching change with the angles of inclined layers. In addition, the earth pressures acting on the trap door shows non-symmetrical distributions when the layers are not horizontal. The stress concentration occurs in one side of the rock masses close to the trap door. Furthermore, the surface settlements are also related to the inclined angle, and the loosening zone in rock masses can be different from Terzghi's theory [1]. Since, simulations have good agreements with the laboratory test, it demonstrates the applicability of DDA to explain the mechanical behaviors of tunnel, such as arching phenomenon, non-symmetrical earth pressure distributions acting on the trap door, and the surface settlement profile in the jointed rock masses.

Dans cet article est decrite l'etude numerique du perçage d'un tunnel dans un massif de couches rocheuses jointes inclinees. La simulation à l'aide de l'Analyse de Deformation Discontinue (DDA), en faisant varier l'angle d'inclinaison des couches de roche, nous apporte des resultats en termes de distributions de contraintes et de comportement des couches, resultats qui sont ensuite compares avec des resultats de tests en laboratoire. Les resultats confirment le fait que la DDA est capable de reproduire le phenomène d'arcage autour de la trappe lorsque la trappe s'abaisse. Les formes d'arcage varient selon l'angle d'inclinaison des couches de roche. Par ailleurs, lorsque les couches ne sont pas horizontales, la distribution de pression agissant sur la trappe est assymmetrique. La concentration de contraintes se produit du cote proche de la trappe. De plus, les tassements de surface dependent eux aussi de l'angle d'inclinaison. En consequence, les resultats de simulation sont en accord avec les tests en laboratoire, ce qui prouve que la DDA permet d'expliquer des comportements mecaniques du tunnel tels que l'arcage, les distributions assymmetiques de pression du sol sur la trappe, ainsi que le profil du tassement de surface dans la masse de roches jointes.

Dieser Beitrag beschreibt eine numerische Studie ueber Tunnel im geklueftetem Fels. Das Verhalten und die Druckverteilungen in den unterschiedlich geneigten und gekluefteten Felsenmassen wird mit Hilfe des Discontinuous Deformation Analysis Programms (DDA) simuliert, und mit Laborversuchen verglichen. Die Resultate bestatigen, dass DDA der Gewölbewirkung im „Trapdoor" Experiment gut reproduzieren kann. Die Form des Gewölbes, andert sich mit unterschiedlichen Neigungswinkeln der Schichten. Bei _ geneigten Schichten entstehen unsymmetrische Druckverteilungen. Auch die Oberflachenabsenkung ist von dem Neigungswinkel abhangig. Die gute Übereinstimmung der Simulationen mit den Laborversuchen zeigt, dass die DDA-Methode gut geeignet ist, um das mechanische Verhalten von Tunneln, wie z.B. den Effekt der Gewölbewirkung, die unsymmetrischen Druckverteilungen bei geneigten Schichten, oder die Oberflachenabsenkung in gekluefteten Felsenmassen, zu erklaren.


Many underground constructions, such as tunnel excavations and mining have to be constructed not only in the intact, stable rock mass, however, sometimes in the place with joints, faults, inclined strata and weak zones, etc. During the mountain tunnel constructions, specifically, it is pointed out that the discontinuities affect the behaviors of rock mass very much [2]. To complete the excavations in jointed rock mass successfully, it is necessary to not only guarantee the tunnel stabilities but also understand the mechanical behaviors of jointed rock mass. To solve the problems mentioned above, a discontinuous numerical analysis method named Discontinuous Deformation Analysis (DDA) is introduced in this study. By comparing the simulation results to the laboratory tests, the applying of DDA to solve the two major issues of tunneling, including loosened earth pressure and the characteristics of ground subsidence are discussed.

Laboratory Test with Inclined Layers
Testing Apparatus

Park (2001) [3] and Park et. al. (2001) [4] performed the trap door tests to the inclined layers. The rock mass with inclined layers can be simplified and modeled as assemble of blocks in Fig. 1(a). Two predominant discontinuous planes exist in the model Fig. 1(b).

This content is only available via PDF.
You can access this article if you purchase or spend a download.