1. The strength of rock mass can be well constrained by the topography. Pore pressure distributed in the rock slope is essential for back calculating the strength. The influence of earthquake on the topography needs to be studied. The strength of rock mass can be well constrained by the topography. Pore pressure distributed in the rock slope is essential for back calculating the strength. The influence of earthquake on the topography needs to be studied.  RMR-based slope performance curves Topography, rock mass strength and pore water pressure Jia-Jyun Dong, Yi-Ju Su and Chyi-Tyi Lee Graduate Institute of Applied Geology, National Central University, Jhongli, Taiwan Abstract Relief is a fundamental landscape reflecting the influence of uplift and erosion. Contrary to the traditional concept that the relief is dominated by incision, several researches indicate that the landscape-scale material strength play an important role on the landform process. However, it is difficult to obtain a representative strength parameters based on laboratory rock tests. Slope height and slope angle were frequently used to infer the strength of rock mass. In this research, a series of slope response curves will be proposed to constrain the rock mass strength. Non-linear Hoek-Brown failure criterion will be incorporated into the proposed model where the linear Mohr-Coulomb failure envelop seems oversimplified. Meanwhile, the influence of pore water pressure on the slope stability is considered. Consequently, the strength of rock mass could be inferred from the topography. Cases including stable and failed rock slopes with reported slope height and slope angle are used to validate the proposed model. The result shows that the strength parameter of rock mass could be reasonably inferred from the topography if the pore pressure can be evaluated.Abstract MotivationMotivation  Importance of rock mass strength  How to get representative rock mass strength? –Laboratory tests –In situ tests –Back analysis Scale effect “Scale effect” of rock mass strength Topography data from MOLA + rock mass classification system RMR Methodology - Slope performance curve Rock mass classification GSI, m i =9, (σ ci )= 35 MPa RMR Slope stability analysis FS=1 α=? FS=1 α=? Slope performance curve Result (I) R u = u/σ v =0R u =0.3 Result (III)  Verification of the slope performance curves (Taheri and Tani, 2010) Real GSI Back calculated GSI=30~40 Real GSI=28~33 Back calculated GSI=40 Real GSI=46~50 Back calculated Ru=0.3~0.6. ConclusionsConclusions Bye, A. R., Bell, F. G., 2001. Stability assessment and slope design at Sandsloot open pit, South Africa, International Journal of Rock Mechanics & Mining Sciences, 38, 449-466. Evert Hoek, 2000. Practical rock engineering Scale effect Feasible !! Schultz, 2002 Hoek and Brown Failure Criterion Mohr-Coulomb Failure Criterion σ ci =250MPa σ ci =35MPa m i =5 m i =33 σ ci =3MPa m i =9 Back calculated RMRs are significant lower than the field evaluated RMRs. Effect of pore pressure should be considered.  Measured slope angles and slope heights  GSI-based slope performance curves – dry slope Result (II) Wallrock: 50<RMR<65 Interior deposits: 30<RMR<55 Slope height vs. Slope angle of wallrock and interior deposits in Valles Marineris m i =9, σ ci = 35MPa  GSI-based slope performance curves – wet slope Result (IV) Abstract number: EGU2011-1821; Session NH3.10/GM6.2