Research On Uniaxial Compression Creep Damage Characteristics And Constitutive Model Of Gypsum Rock Under Acid Corrosion

Taking the gypsum rock in the gypsum mining area of Linli County,Changde,Hunan province as the research object,uniaxial compression test and triaxial compression test were performed on the gypsum rock using the RYL-600 the shear rheology equipment and MTS815 Rock Mechanics Testing System,compression creep test were performed on gypsum rocks under the conditions of p H = 7 water,p H = 6 and p H = 5 hydrochloric acid solution,and SU3500 electron microscope scanner was used to conduct electron microscope scan tests on gypsum rocks before and after acid corrosion.Based on the uniaxial creep test of gypsum rock,a Burgers model and NVPB model were used in series to establish a nonlinear creep constitutive model to describe the creep characteristics of gypsum rock under acid corrosion conditions and verified.A series of studies have shown that:(1)Under uniaxial compression,the process from the beginning of loading to the failure of the gypsum rock specimen is mainly divided into the original frature compaction stage,the elastic deformation stage,the plastic deformation stage,and the post-destruction stage.The rock samples are mainly single-slope shear failure and the X conjugated incline plane shear failure,with tensile failure.Under the condition of triaxial compression,the triaxial compressive strength,residual strength and deformation parameters of gypsum rock increase correspondingly with the increase of confining pressure.Gypsum rock under triaxial compression with a confining pressure of 10 MPa is brittle,20 MPa and 30 MPa are ductile.The main morphology of gypsum rock is incline plane shear failure.(2)For the uniaxial compressive creep test under acid corrosion conditions,the three groups of test specimens are loaded with three stress levels in the first dry state,and the strain increments of the three groups of specimens are almost the same.Little discreted,reliable test results.During the second loading,the sample was damaged due to the addition of water and acid.The gypsum rock specimens with hydrochloric acid at p H 5 were destroyed at the first stress level,the gypsum rock specimens with water added to p H = 7 and a hydrochloric acid with p H 6 all suffered damage at the second stress level;the three groups of specimens had basically the same failure mode,with splitting and varying degrees of end damage.The difference was that the failure time of the former is earlier than the latter,which indicates that the stronger the acidity,the greater the effect on the creep of the sample.(3)From the microstructure,the dry sample structure is tight and complete,and the whole is more homogeneous.However,the rock sample soaked with water and acid has significantly increased and very dense pores,with larger pores appearing and loose structure,the pores have increased sharply,and the indication of rock samples has almost become a "hole".Non-hydrophilic minerals and minerals that cannot react with hydrochloric acid are exposed on the surface of rock samples.(4)A new nonlinear creep constitutive model was established by using the Burgers model in series with the NVPB model to describe the creep characteristics of gypsum rocks under acid corrosion conditions.(5)The parameters of the creep model identified by Origin software were verified by the comparison between the experimental curve and the fitted curve,which proved the correctness and rationality of the model.