Abstract: Based on the in-situ uniaxial compression rheological tests on the weak intercalations and on the fault fragmentation zone ,time-effect on deformation and failure mechanism of the weak rock mass is investigted. The method of determining long-term strength of weak intercalations , empirical formula and influencing range of the time-effect on the various tests are made and the met of determining different stages of rheological process and long-term strength are discussed in detail .