EXPERIMENTAL STUDY ON DIRECT SHEAR CREEP OF CHANGCHUN STRONG WEATHERED MUDSTONE

Changchun subway tunnel excavated through the strong weathered mudstone layer, strong weather mudstone belongs to the weak rock, it has rheological properties, and it has very significant impact on the stability of the subway tunnel and other underground structure. The study on the creep mechanics characteristics of weak rock mass can provide the theoretical basis for the surrounding rock of the subway tunnel and the design of the underground structure. The strong weathered mudstone sampling was carried out in the excavation surface of the subway tunnel in the study area. Direct shear creep tests were carried out the creep characteristics of strong weathered mudstone were obtained. The long-term strength of mudstone was obtained by different methods:transition creep law, the first inflection point method and isochronous curves method, and the results were compared and analyzed. The results show that the long-term strength of mudstone is obviously reduced compared with the instantaneous strength,c/c is 20%~40%, and tan/tan is 60%~70%.Therefore, it is necessary to use the long-term strength index as a reference in the actual design of rock engineering.