Study On The Evolution Of Pore Structure And Creep Features Of Sandstone Under The Coupling Action Of Stress And Seepage Flow Of Chemical Solution

Rock mass is the typical geologic material under the multi-field coupling actions including infiltration and corrosion of ground water, temperature variation and rock stress field. So far, the study on physical and mechanical characters under multi-fields coupled has been a basic topic for the stability analysis of engineering structures including slopes, dam foundation, tunnels, radioactive waste underground repositories and underground energy repositories, etc. The relative works have the important scientific values and applicability. However, ground water is a kind of complicated solution with a certain pH value and composed of many kinds of ions. The micro-structure of rock will change with the reaction between minerals of rock and chemical solution. So pore size and physical and mechanical characteristics of rock will be changed at the same time. These changes will influence the stability of engineering structures. So the research on evolution of rock porosity structure and its deformation characteristics during corrosion of rock exposed to different hydrochemical solutions is of theoretical significance and applicable valuable for evaluation of long term stability of rock engineering and waste disposal in environment engineering.Serious red sandstone from Longyou is taken as research object, variation of rock microstructue, composition of minerals and porosity structure under the conditions with different hydrochemical solutions are analyzed qualitatively and measured quantitatively. According to chemical nature of reaction between hydrochemical solution and rock minerals, mathematical model of corrosion amount of rock minerals and variation of rock porosity is established based on physical and mechanical actions of mineral solution, migration and adsorption. Following that, the numerical simulation of the experiment process is carried out. Uniaxial static creep test of sandstone exposed to different hydromechanical solutions and triaxial creep test of sandstone exposed to different hydrochemical solutions with different permeable pressure are carried out. Through analysis of the test data, the regulation of deformation ageing of sandstone in the different multi-field coupling environments and deformation regulation of sandstone in mechanics-hydraulic-chemistry coupling environment are obtained, and then corresponding creep model is established. The main contents of the thesis are represented as following:1. Corrosion tests of sandstone in the different hydrochemical environments were carried out. Microstructure, composition of minerals and element content of sandstone before and after corrosion were measured and anal sized. At the same time, porosity of sandstone and pH value of solution during the course of corrosion were obtained. Variable characteristics of microstructure of sandstone samples before and after corrosion in the different hydrochemical solutions and rules of porosity variation of sandstone vs. time were also obtained.2. According to the nature of reaction between hydrochemical and rock, main chemical reactions of minerals in different hydrochemical solutions were obtained through tests and theoretical analysis. Based on the theory of chemical kinetics, chemical thermodynamics, and solute transportation, a reactive-transport mathematics model was established. Temporal and spatial distribution characteristics of precipitation amount of minerals in sandstone and dynamic evolution regulations were presented by numerical analysis. And the results of numerical analysis agree well with the test data.3. A system of the test device for uniaxial compress creep tests for rock in mechanicics-hydraulic-chemical environment were developed and calibrated by author. Then it was adopt to study rock creep in the environment of different hydrochemical solutions and carry out rock uniaxial creep test in the coupling environment of chemical and hydraulic. Through the analysis of the test results, it can be seen that hydrochemical solutions have chemical disturbance effect on rock in stable creep state and the chemical disturbance effects are different with different hydrochemical solution. Through theoretical analysis, creep deformation regulation of rock in the hydrochemical-hydraulic coupling environment and influence of creep effect on rock microstructure were explained.4. Rock porosity real time measuring instrument in the environment with chemical permeability-creep coupling were developed and calibrated by author. Then it was adopt to carry out triaxial creep test of sandstone. The porosity and permeability coefficient of sandstone samples were real-time measured. The regulation of creep deformation and the evolution of permeability characteristics of sandstone samples were obtained. By the observation of sandstone samples by SEM, the influence of creep effect of sandstone samples with chemical permeability pressure on microstructure of sandstones was analysized. 5. The results of triaxial creep test of sandstone exposed to different hydrochemical solutions indicates that creep deformation regulation of sandstones agree well with general Kelvin model. The least square method based on the pattern search method was improved with the Marquardt method, and the program was developed with VC. The rheological models and parameters were recognized by the improved method. The prediction results are in good agreement with the test results.