RESEARCH ON CREEP CHARACTERISTICS AND CONSTITUTIVE MODEL OF RED BED MUDSTONE UNDER SATURATED-DEHYDRATED CYCLE

The red bed soft rocks in central Yunnan are widely distributed and have significant rheological properties. In order to study the creep properties of red bed mudstones under saturated-dehydration cycle conditions,Longchuan River valley mudstones are used as research objects. YZJL-300 rock shear rheometer performs 30,50,and 100 shear creep tests on saturated-dehydration cycles. A constitutive model of mudstone creep is proposed by analyzing the shear creep characteristics of mudstone. The test results show that:(1)the limit instantaneous creep rate gradually increases 0.273 mm·h^-1,0.365 mm·h^-1,and 0.452 mm·h^-1 as the number of saturated-dehydrated cycles increases and the long-term strength gradually decreases; (2)under the same shear load,the greater the number of cycles,the lower the viscoelastic modulus of mudstone; the same number of cycles,the larger the shear load,the smaller the viscoelastic modulus of mudstone. The function of the number of cycles and time is E(n,t). A non-linear viscoplastic body is introduced to establish the shear creep constitutive model(LCJN) of the inverted siphon mudstone of the Longchuan River and a general global optimization method to identify parameters of LCJN model,and verify the accuracy and applicability of the model.