Tang Liansheng, Chen Yang, Jian Qinglin, Cheng Zihua, Ding Weiya
School of Architectural Engineering, Guangzhou Institute of Science and Technology, Guangzhou, 510540, China.
School of Earth Sciences and Engineering, Sun Yat-Sen University, Zhuhai, 519082, China.
Sci Rep. 2024 Aug 28;14(1):20014. doi: 10.1038/s41598-024-71117-8.
Different chemical solutions can significantly change the contact angle (CA) of soil, but few studies have studied the change rule and action mechanism of the CA from the mineral composition of soil essence. In unsaturated soil mechanics, the CA is an important parameter to calculate the wet suction between soil particles in unsaturated soil. When the chemical composition of the soil pore liquid changes, the CA will also change, which will affect the wet suction and other parameters, thus changing the macroscopic mechanical properties of the soil. In this study, the CA of air-solution-mineral phases with different solution components (pH, type and concentration of salt solution) of different minerals (quartz, orthoclase and plagioclase) were measured. The results show that the CAs of quartz, orthoclase and plagioclase all rise first and then drop with the rise of pH. The peak CAs are pH = 5, pH = 4 and pH = 3, respectively. Quartz, orthoclase and plagioclase all have valley values in different concentrations of NaCl and KCl solutions. In CaCl solution, only quartz has valley value, while orthoclase and plagioclase increase monotonously. Quartz in soil plays a main role in the influence of soil CA, followed by orthoclase and plagioclase. The CA of different minerals in different chemical solutions is mainly controlled by electric double layer interaction and functional groups interaction. In different salt solution environment, in addition to the above two effects, the mineral CA is also affected by the surface tension.
不同的化学溶液会显著改变土壤的接触角（CA），但很少有研究从土壤本质的矿物组成方面研究接触角的变化规律及作用机制。在非饱和土力学中，接触角是计算非饱和土中土颗粒间湿吸力的一个重要参数。当土孔隙液的化学成分发生变化时，接触角也会改变，这将影响湿吸力等参数，进而改变土的宏观力学性质。本研究测量了不同矿物（石英、正长石和斜长石）在不同溶液成分（pH值、盐溶液类型和浓度）下的气-溶液-矿物相的接触角。结果表明，石英、正长石和斜长石的接触角均随pH值的升高先增大后减小，峰值接触角分别为pH = ５、pH = 4和pH = 3。石英、正长石和斜长石在不同浓度的NaCl和KCl溶液中均有谷值。在CaCl溶液中，只有石英有谷值，而正长石和斜长石单调增加。土壤中的石英对土壤接触角的影响起主要作用，其次是正长石和斜长石。不同矿物在不同化学溶液中的接触角主要受双电层相互作用和官能团相互作用控制。在不同的盐溶液环境中，除上述两种作用外，矿物接触角还受表面张力的影响。
