Three large slopes will be cut in a highly weathered rock to construct a highway along the eastern coast of Korea. RMR method was used to estimate geotechnical parameters of the in-situ rock mass. Stability analysis has been conducted by limit equilibrium method for the slopes preliminarily designed according to the guideline recommended by Korea Highway Cooperation. Slope gradients were adjusted and adopted for the slope design after their safety factor has been examined again. Their stability was finally checked out by numerical analysis using FLAC.


Trois larges versants seront faits dans une roche hautement desagregee pour construireune autoroute Ie long de la côte de l'est de la Coree. La methode de RMR a ete utilisee pour estimer les parametres geotechniques du massif rocheux, L'analyse de stabilite a ete conduite par la methode' de I'equilibre limite pour les versants preliminairement dessines d'apres Ie standard recornmende par Korea Highway Cooperation. Les rampes de versant ont ete adjustees et adoptees pour le dessin du profil apres leurs facteurs de securite a ete reexamines. Leurs stabilite ont ete finalement verifiee par I'analyse numerique à I"aide de FLAC.


Drei, große Böschung werden im hoch verwittertem Gebirge sein geschnitten, urn die öffentliche Straße langs der östlich Kueste von Korea zu konstruieren. RMR Methode wird benutzt, um die geotechnische Einflußgröße von in-situ Gebirgsmasse zu veranschlagen. Die Analyse der Stabilitat ist durch die Methode vom abgrenzendem G1eichgewicht fuer die vorplanende Böschung gemaß der Fuehrung, empfohlen von Korea Highway Cooperation, anfuehren geworden. Die Böschungsneigung wurde fuer die Böschungsanlage eingestellt und angenommen, nachdem der Sichheitsfaktor nachpruefen geworden ist. Schließlich ihr Stabilitat durch die numerische Analyse mit der Anwendung von FLAC geprueft wird.


A highway running from Donghae City to Jumunjin City will be constructed along the eastern coast of Korea. Figure I shows a section of the planned line of 3,8S8m long. In this section three large slopes marked as A, B and C as well as three tunnels are to be constructed.. The dimension of the slopes will be approximately 40, 30 and 50m high and 120, 100 and 210m wide, respectively.

Rock mass -in this region is highly weathered and contains well-developed joints and discontinuities since this region has suffered a number of tectonic activities. This makes difficult to characterize' geotechnical properties of in-situ rock. RMR method proposed by Bieniawski(l989) was introduced to define appropriate material parameters of rock mass under such circumstances.

Slope design procedure based on the induced geotechnical properties is presented. and followed by stability analysis. Stability analysis of the slopes has been executed using both limit equilibrium and numerical methods.


Geological structure was investigated by borehole logging. The surface layer is composed of a weathered soil of 2 to 6m thick. Rock layers under the soil layer are classified into three groups from weathered to moderate according to the weathering state, discontinuities, uniaxial compressive -strength and so on as shown in Figure 2.

Weathering rate is significant in, weathered rock layer.

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