(1. Key Laboratory for the Exploitation of Southwest Resources and the Environmental Disaster Control Engineering，Ministry of Education，Chongqing University，Chongqing 400030，China；2. Institute of Geotechnical Engineering，Chongqing Jiaotong University，Chongqing 400047，China)
Abstract：In order to understand the creep characteristics of fractured sandstone，a series of creep tests of fractured sandstone from T3xj6 sandstone in Yongchuan mine are carried out by a MTS815 rock testing system；and the whole process of fractured sandstone is described with modified Nishihara model. The results show that creep law of fractured sandstone is similar to those of the general creep characteristics of coal and rock. Fractured sandstone also has long-term strength，which is determined according to the stress-strain relationship obtained by theoretical analysis. The whole process of fractured sandstone can be described with modified Nishihara model. When load stress is greater than long-term strength of fractured sandstone，unknown parameters of modified Nishihara model could be achieved with least squares method. The homogeneity，load control and leak tightness of rock samples can influence the successful creep of fractured sandstone. These results have great significance to revealing time lag of underground engineering disasters；and supporting parameters of surrounding rock mass in excavation roadway can also be determined.
