Abstract: Lubuge Dam was completed in l989 and has experienced the full reservior filling.Observationdata during both construction stage and operation stage and results of large dlameter triaxial test ofsampleS trom the filied embankment have been used to verif the conStitutive models of soil and rockmateriajs and tO back analyze some model constants which can hardly be determined in laboratory.Comparison of computed results with the observations showed that the Duncan’s hyperbolic model al-ways overestimates the horizontal movement of dam body,while the double-hardening model proposedby the author gives much better results for both settlements and lateral movements.In order to have abetter agreement between computation and observation,it is necessary to take the time dependentcreep deformation into account.There fore a model of creep deformation is presented and its constantsare determined through back analysls.