Tests on shear strength deterioration of sandstone under the action of chemical solution and drying-wetting cycles and analysis of chemical thermodynamics
LIU Xinrong1，YUAN Wen1，FU Yan2，WANG Zijuan1，MIAO Louli1，XIE Wenbo1
(1. College of Civil Engineering，Chongqing University，Chongqing 400045，China；2. Faculty of Construction Management and Real Estate，Chongqing University，Chongqing 400045，China)
Abstract：In order to study the deterioration of shear strength of sandstones，specimens were tested through UCS and TCS after different wetting and drying cycles in the environment of different pH values. The cohesion and internal friction angle were calculated，and the relation among the cohesion，internal friction angle and number of cycles was determined and the relationship between the shear strength and the number of cycles in acid and alkali environment was obtained. According to the mineral compositions of sandstone and their contents，the chemical reaction equations of the main mineral in neutral，alkaline，acidic solutions were obtained. The stability of the minerals in the neutral，alkaline and acidic solution was therefore interpreted based on the basic principle of chemical thermodynamics. In order to verify the correctness of the analysis，the concentrations of some ions(Ca2+，SiO2，Na+，K+) in the soaking solution were measured. The results show that the deterioration of the shear strength sandstones is most serious in the acidic environment，secondly in the alkaline environment，and least in the neutral condition. The main compositions of cement，calcite and feldspar，which have a great influence on the shear strength，are unstable in the acid environment because the dissolution reaction occurred spontaneously. The quartz，the main composition of aggregate having little influence on shear strength，is unstable in the alkaline environment with the dissolution reaction occurred spontaneously. The measured concentration of Ca2+，Na+，K+，dissolved from calcite，sodium feldspar，potassium feldspar in acid solution，were significantly higher than that in the neutral and alkaline solution，while the measured concentration of SiO2，dissolved from quartz in the alkaline solution，was significantly higher than that in the neutral and acid solution，which are consistent with the result from the thermodynamic analysis.
刘新荣1，袁 文1，傅 晏2，王子娟1，缪露莉1，谢文博1. 化学溶液和干湿循环作用下砂岩抗剪强度劣化试验及化学热力学分析[J]. 岩石力学与工程学报, 2016, 35(12): 2534-2541.
LIU Xinrong1，YUAN Wen1，FU Yan2，WANG Zijuan1，MIAO Louli1，XIE Wenbo1. Tests on shear strength deterioration of sandstone under the action of chemical solution and drying-wetting cycles and analysis of chemical thermodynamics. , 2016, 35(12): 2534-2541.
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2016, Vol. 35 
