Failure analysis of modular-block reinforced-soil walls during earthquakes

Several modular-block reinforced-soil retaining walls failed during the 1999 Ji-Ji (Chi-chi) earthquake of Taiwan. Similar walls showed distress during the 1994 Northridge, Calif., earthquake. The instability or failure of these walls offered an opportunity to validate the simplistic pseudostatic limit-equilibrium procedures. In this study, the Ta Kung Wall of the Ji-Ji earthquake is analyzed, and the Gould and Valencia Walls of the Northridge earthquake are revisited with an improved estimation of local site acceleration. The local acceleration was estimated by using simple attenuation relationships obtained through the earthquake records. The results of analysis indicate that these three walls had adequate internal stability under estimated site acceleration. The geosynthetic length was inadequate to resist compound modes of failure where the potential failure surface extends beyond the reinforced zone. The external stability was most critical in the presence of horizontal and vertical accelerations.