基于分形理论的粉砂质泥岩酸雨崩解特征研究

    SLAKING CHARACTERISTICS OF SILTY MUDSTONE UNDER ACID RAIN ACTION BASED ON FRACTAL DIMENSION

    • 摘要: 黏土岩的崩解过程易受环境条件(如崩解液特征)影响,酸雨作用对其影响显著,但其酸雨崩解特征有待研究。目前对黏土岩崩解特征的评价多采用耐崩解性指数,仅考虑崩解后大于2mm的残留颗粒质量,未反映崩解后的整体粒径分布特征。本文以典型酸雨区攀枝花机场滑坡为依托,选取滑带粉砂质泥岩,开展不同pH值条件下的岩石崩解试验;引入分形理论,建立分形维数与酸雨历时、降雨酸度间的相关关系,定量刻画粉砂质泥岩酸雨崩解特征及影响因素;采用电感耦合等离子体发射光谱法分析不同酸度崩解溶液的离子成分差异,以探索降雨酸度造成岩石崩解特征差异的本质原因。结果表明:采用分形理论可以较好地反映粉砂质泥岩酸雨崩解特征,分形维数越大,粉砂质泥岩崩解程度越大;分形维数与酸雨历时、降雨酸度之间皆存在明显对数正相关关系;不同降雨酸度粉砂质泥岩崩解特征存在差异的原因在于白云石、方解石溶蚀程度不同。研究成果可为酸雨地区黏土岩的工程性质评价提供参考。

       

      Abstract: Slaking process of claystone is vulnerable to environmental condition. The acid rain can significantly affect the process. The corresponding mechanism remains to be studied. Traditionally, the slaking characteristic of claystone is evaluated by second cycle slake durability index which is determined by the mass of the residual particles larger than 2 mm only. Such evaluation fails to reflect the characteristics of the overall particle size distribution. This paper takes the Panzhihua landslide as an example. The site is located in the typical acid rain area. The silty mudstone samples located on the sliding surface are processed. Then a series of slaking experiments are carried out by the use of solutions with different pH values. Based on the fractal theory, the fractal dimension is introduced to quantitatively describe the slaking characteristics of silty mudstone. The correlations between fractal dimension with acid rain duration and acidity of rainfall are established, respectively. The substantial cause for the slaking characteristic differences due to different rainfall acidity is determined through analyzing the solution chemical composition. The results highlight that the fractal theory can better reflect the acid rain slaking characteristics of silty mudstone. The higher the fractal dimension is, the higher the slaking degree. The logarithmic positive correlation exists between the fractal dimension and the duration of acid rain, the final fractal dimension and the acidity of rainfall. The reason for the slaking characteristics difference under various rainfall acidities lies in the different degrees of dolomite and calcite dissolutions. Conclusions of this paper can be taken as references for engineering property evaluation of rock mass in acid rain area.

       

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