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| Experimental study on the mass transfer-deterioration process of basalt under drying-wetting cycles and chemical reaction |
| SHEN Linfang，DONG Wushu，WANG Zhiliang，XU Zemin，ZHU Weiming |
| (Faculty of Civil Engineering and Mechanics，Kunming University of Science and Technology，Kunming，Yunnan 650500，China) |
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Abstract Under the effect of continuous drying-wetting cycles，the rock mass in the water-level-fluctuating zone of reservoir would experience the weathering aggravation and the mechanical properties deterioration. Cyclic drying-wetting tests were carried out under the conditions of pH = 3，7 and 11 respectively using basalt samples. The degradation laws of uniaxial compressive strength of basalt under different pH and cycles were discussed. Chemical composition of solution were tested to analyze the mass transfer between solution and rock. Based on the basalt dissolution kinetic theory，the effect of reaction processes on strength degradation were studied. The results showed that the uniaxial compressive strength decreases with the increase of cycles in all of the three solutions. While there were significant differences in the decline level during the early stage. Acid condition exhibited the most severe corrosion impact on strength，neutral the moderate，alkaline the least. In the mid-late stage，the difference was minimized. The final deterioration level was almost the same in three solutions. The water-rock reaction in acid and alkaline condition underwent a transition from non-equilibrium to equilibrium. In neutral condition it was always in non-equilibrium state. The elements releasing order in non-equilibrium process under different pH condition obeyed the same rule，which were Ca the first，Al the second，and Si the last. In equilibrium reaction，precipitation and replacement of Al occurred on the solid phase surface. Precipitation would inhibit the release of Si，while replacement would promote the release of Si. The deterioration degree of rock strength in neutral solution was controlled by the stoichiometric dissolution in non-equilibrium state. In acidic and alkaline solutions，the strength degradation of rock was affected by the formation rate of Al precipitation in the early stage，and the replacement of Al in the later stage. The research results could provide scientific basis for evaluating the long-term stability of reservoir slope in basalt area.
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2021, Vol. 40 
