软岩在饱水过程中水溶液化学成分变化规律研究

TESTING STUDY ON VARIATION REGULARITIES OF SOLUTION COMPONENTS IN SATURATION OF SOFT ROCKS

针对广东地区重大工程中几种典型软岩的基本类型和特点,设计了一系列软岩饱水软化试验。通过选取华南地区“红层”——粉砂质泥岩和泥质粉砂岩两种代表性软岩,在天然状态、饱水1,3,6和12个月时,研究水溶液pH值和阴离子及阳离子浓度的变化,探讨不同类型软岩在不同饱水时间后,水溶液的pH值和化学成分的动态变化规律。结果表明,软岩在饱水过程中,水溶液的pH值将逐渐减小,由弱碱性向酸性过渡,这些变化率为2%～46%。同时,着重指出:饱水3个月时,是水-岩化学作用的临界时间转折点,即3个月之前,阳离子及阴离子的化学交换与吸附作用活跃,反应中离子的浓度是下降的;3个月之后,该作用逐渐减弱,离子的浓度呈现出回升渐趋稳定或稳定的趋势。软岩与水化学反应中离子浓度的变化一般服从两种曲线类型,即指数曲线和动力学稳定方程(反应-扩散方程)曲线。其动力学过程无论服从哪一种规律,最后终将趋向稳定态。此外,对于这两类软岩,其-F,Mn2+,Al3+,Fe3+,Zn2+等离子在试验过程中基本保持稳定值,表明岩块与水的化学作用过程中基本没有该类离子的参与。

Based on the research of classification and features of some typical soft rocks in a certain major project in Guangdong province, the authors design a series of tests for the interaction between soft rocks and water. Two typical rocks distributing in south China area, silty mudstone and mud siltstone, in natural state or saturated for 1, 3. 6 and 12 months, are studied to obtain variation regularities of concentration of cations, anions and pH value of solution and the dynamic evolution regularities of solution components for different soft rocks. The results show that during the saturation process, the pH value of the solution declines, the solution turns from light alkalescence to acidity, and the rates of that transformation are 2%-46%. Meanwhile, it's pointed out that the critical turning point of the interaction between water and rock appears at the time of 3 month. In the first 3 month, the exchanging and adsorption action of positive and negative ions are all active, the concentration of the ions decline during the reaction process, and in the following 3 month, the reaction gradually weakens, and the consistency of ions presents an ascending and stable trend. The concentration of ions in the reaction between soft rock and water are generally coincident with two types of curves, exponent curve and curve of dynamic stability equation. No mater what regularity the dynamic process is consistent with, it will ultimately turn to a stable state. In addition, the concentration of F-, and Mn2+, Al3+, Fe3+, Zn2+ in the tests on the two kinds of soft rock, almost maintains stable value, which suggests that these ions almost do not participate in the reaction between rock and water.