Study On The Damage And Creep Characteristics Of Red Mudstone

It is of great theoretical value and practical significance to study the instantaneous and rheological mechanical properties and models of rock under different water-bearing conditions for correctly predicting and effectively controlling the safety and stability of rock engineering.In this paper,the red layer mudstone of Shizishan landslide in Xinjin County,Sichuan Province is taken as the research object.By means of experimental study and theoretical analysis,the instantaneous creep mechanical properties of red layer mudstone under different confining pressure and different bubble time are studied.The statistical damage softening model and creep damage model of red layer mudstone are established,and the secondary development of improved Burgers creep damage model based on FLAC^3D is carried out.The main work of this paper is as follows:?1?Under the same confining pressure,the peak strength and modulus of elasticity of mudstone decrease with the increase of bubble water time under the same confining pressure.Under the same confining pressure,the peak strength and modulus of elasticity of mudstone are all with confining pressure under the same water saturation condition.Under the same confining pressure,the peak strength and modulus of elasticity of mudstone decrease with the increase of water time.Under the same water condition,the peak strength and modulus of elasticity of mudstone are all with the confining pressure under the same water saturation condition.In order to correctly describe the stress strain curve of the mudstone,a statistical damage softening model is constructed,which is based on the modified Harris function to establish the damage evolution equation,which is based on the modified Harris function.The strength of rock micro element obeys the improved Harris probability density distribution,selects the DP-3 strength criterion and considers the damage variable correction.Through the model verification of the two long granite and sandstone test data in the red mudstone and the related literature,it proves the rationality and applicability of the model,analyses the expansion process of cumulative damage,and puts forward the initial damage system.The latter is a new discovery.The latter model is by introducing a statistical damage constitutive model which has been considered in the stage of voids compaction.Based on the Harris damage evolution equation built in this paper,a statistical damage softening model can be obtained to identify the five stage stress and strain of the red mudstone.?2?The triaxial compression creep tests of red mudstone with different bubble time and confining pressure were carried out,and it was found that red bed mudstone had remarkable nonlinear rheological characteristics.The characteristics of strain,creep rate,long term strength and long term shear strength of mudstone under different working conditions are analyzed,and the variation law under different working conditions is summarized.The improved Burgers creep damage model and the creep damage model based on fractional calculus are constructed by studying the creep law of red mudstone.The former is based on the traditional Burgers model.The damage variable is defined by an improved Harris function,and a viscoplastic body considering damage is connected in series.According to the theory of damage mechanics and introducing Kachanov creep rate,the latter model establishes an elastic body which considers aging damage in the process of creep damage,and defines viscous body and viscoplastic body based on fractional calculus.In series,the creep damage model based on fractional calculus is obtained.The two creep damage models are compared and verified.It is found that the two models can well reflect the whole creep process of red mudstone.The creep damage model based on fractional calculus is better than the improved Burgers creep damage model in identifying the creep data of red mudstone.?3?The finite difference expression of the improved Burgers creep damage model is derived.Based on the built-in source code of the Burgers model,the secondary development of the improved Burgers creep damage model is realized by using VC programming language on the FLAC^3D platform.The secondary developed creep damage model is tested by triaxial compression creep simulation test.The simulation results are in good agreement with the theoretical calculation results.The inversion verifies the correctness of the model parameters and verifies the feasibility of the secondary development of the rheological model.?4?In this paper,the damage evolution equations of both the statistical damage softening model and the improved Burgers creep damage model are built on the basis of the improved Harris function,which can accurately reflect the damage and creep characteristics of red mudstone.It is proved that the damage evolution equation based on improved Harris function is correct and reasonable.Harris function is rarely used in the construction of statistical damage model and creep damage model.The model construction and analysis provide a reference for the application and extension of Harris damage expression in damage mechanics and constitutive theory.