| Corrosive environmental water,extensively existing in earth’s surfurce, has physical,chemical and mechanical effects on rockmass,when the water contacted with rockmass. The deterioration problem of rockmass mechanical property would caused by chemical corrosion,such as slope, dam foundation, unstable rock, stone cultural heritage, and nuclear waste disposal site. These researches related to chemical corrosion is one of foundamental research subjects in many rock enginnering projects. And also, it’s an essential issue about evaluating the design and service period of rockmass engineering. Therefore, study on the rockmass mechanics under chemical corrosion condition could promote theoretical knowledge in laboratory. And it also has great sinigficance and application significance for rockmass projects under chemical corrosion environment.In this paper, taking the Guankuo Formation silty mudstone, Upper Cretaceous, in Sichuan Basin as research project. The corrosion experiments were taken in which the silty mudstone was soaked in different pH acidic water,then the physical,morphological,and mechanical property of silty rock would be tested from macro-mesoscopic perspective.Firstly, the chemical damage mechanism and mechanical degradation of corroded silty mudstone has been analyzed. Secondly,the rock crack process image was obtained by CT technique when the corrode slity mudstone under triaxial compressive condition. And also,the mesoscopic damage and crack propagation mechanism of corroded mudstone, which soaked in different pH acidic water and under triaxial compressive condition,are expounded synthetically. At lastly, we built the creep damage model based on the chemical damage variable, which acquired from the creep experiment under uniaxial compressive condition.The main achievments are summarized as follow:(1) The soaked solution ion feature and formed causes are systematically analyzed with hydrochemical, statistical, and hydrogeochemical simulation methods. And then, chemical damage mechanism of silty mudstone under acidic environmental condition is expounded synthetically. The main mechanisms of acidic water-mudstone chemical reaction include dissolution, hydrolysis, hydration, ion exchange adsorption, and clay mineral expand or disintegration. The silty mudstone would occur dissolution when solution pH<3, but it would occur other meachisms when pH≥5. The solution would be gradually get equilibrium state with soaked time increased under a limited and sealed environment.(2) The morphological, mineralogical composition were measured by X-ray diffraction(XRD) and Scanning electron microscope with Energy disperse spectroscopy (SEM-EDS).The results indicated the rock micro-structure, secondary crack, and pore all changed under chemical corrosion caused by acidic water. The corrosion effects increased with pH decrased.The microstructure showed mineral cementation became loose with soaked time. Most of large mineral crystals evolved into silt particles , which appeared the loose porous structure.The mineral connection type include plane-plane, and angular-edgee, etc., in corroded silty mudstone.(3) Based on triaxial compression experiment, the strength and deformation features of corroded silty mudstone were attained from different confining pressure. Then,the strength and deformation change with pH and soaked time are discussed during acidic water-rock chemical interaction. Therefore, the rule and mechanism of mechanical degradation are interpreted preliminarily. The experiment indicated the cohesion (c), interal frictional angle(φ), and elasticity modulus (E) all decreased with pH decreased and soaked time increased.(4) Based on the CT technique experiment under triaxial compressive condition, the micro-crack initiation, extend, and cutthrough processes real-time images of corroded mudstone in preset level are acquired. The length, width, overlapping model of micro-cracks would be changed under triaxial compression. The rock fracturing process coupled with mechanics effects are explained and interal mesoscopic damage extension mechanisms are attained by these CT images.(5) Based on the uniaxial compressive creep experiment of silty mudstone under different pH solution,the creep characteristics and rule of rock are acquired. The results showed that the rock creep features are obviously affected,when acidic solution pH<3.Based on fractional-order calculus theory, we will software components embedded in the traditional visco-elastoplastic model to establish a fractional-order visco-elastoplastic creep model,which can reflect the rheological characteristics of corroded silty mudstone. Then,the chemical damage variable, which can describe stress and time effects, placed at accelerated creep phase to build a fractional-order visco-elastoplastic creep damage model. Compared with experiment data and this fractional-order visco-elastoplastic creep damage model fiiting data, the results indicated this derived model could effectively describe overall creep characteristics of silty mudstone under acidic solution. |
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