Creep behaviour of saturated purple mudstone under triaxial compression

Abstract

Many landslides have occurred in the purple mudstone of the Middle Triassic Badong Formation (T2b), which is widely distributed in Chongqing City and western Hubei Province, especially in the Three Gorges Reservoir Area (TGRA), China. To investigate the long-term stability of engineering supporting structures for landslides and the deformation control and prediction of rock slopes, triaxial compression tests and triaxial creep tests are performed on the purple T2b mudstone under three low confining pressures (i.e., 1.0 MPa, 3.0 MPa, and 5.0 MPa), and the initial axial stress of creep is set as 35% σp, 45% σp, 55% σp, 65% σp, 75% σp······. The creep viscosity coefficient in the accelerated creep stage is discussed, and an extended Burgers model is proposed with a new Newtonian body. The proposed model fits the test data well in all three creep stages and its parameters can be derived from the data. Compared with the triaxial compression test, the internal friction angle and cohesion inferred from the Mohr circles of the creep tests are reduced by 19.6% and 22.3%, respectively. Accordingly, in the design of retaining and protecting structure to prevent landslides and rock slopes located in the T2b stratum, the effect of creep should be considered.