Mechanical Damage and Chemical Dissolution Kinetic Features of Limestone under Coupled Mechanical-Hydrological-Chemical Effects

To address the mechanical damages of limestone under the coupled mechanical(M)-hydrological(H)-chemical(C) effects, we performed uniaxial compression experiments and dissolution kinetics experiments on limestone in flowing and static solutions for different lengths of time. Through experiments, the peak strengths of the limestone under coupled MHC effects for different time lengths and the major ion concentrations in solutions were obtained. By analyzing the strength damage and chemical dissolution kinetic characteristics, we achieved the strength damage equations and chemical dissolution kinetic equations. Results show that when the solution shifted from the static state to the flowing state, and as its acidity increased, the peak strength loss of the limestone rose as well. The solution mobility had a more significant impact on the peak strength loss than the solution pH value. The limestone dissolution in flowing water was higher than in static water, indicating that solution mobility would promote the limestone dissolution. Among the contributing factors to limestone dissolution, the solution pH value showed the strongest impact, followed by the common-ion effect and then the salt effect. The research result is expected to provide a theoretical basis for maintaining the stability of rocks in geotechnical engineering practice and protection of stone cultural relics.

The morphological variability of Maltese ‘cart ruts’ and its implications

Hundreds of ‘cart ruts’ – pairs of incised parallel grooves in the bedrock – are found across the Maltese archipelago in the central Mediterranean. The age, functional association, formation processes, and taphonomic alteration of these ruts, which occur here with a globally unrivalled frequency, has been much debated. Generally seen as being created by erosion from vehicles such as wheeled carts, or alternatively being cut into the rock to facilitate movement of such vehicles, specific models range from the use of carts to move soil in the Neolithic to them reflecting classical era stone quarrying, and many other possibilities. One interesting aspect concerns the morphological variability of the cart ruts, such as the notion that they have a standard gauge (width between ruts), and that this gauge is very similar to that of modern railway tracks. Evaluating the morphological variability of the cart ruts contributes to an understanding of the phenomenon, as, for instance, we might expect that if they date to different periods, with different functions, and/or were extensively modified by geomorphological processes this will be reflected in the character of their morphological variability. The analysis suggests that cart ruts are fairly standardised in terms of basic measurements such as widths and depth, perhaps suggesting that they are of a consistent age and function. This study identified a need for definitional clarity as the commonly cited gauge measurements are not taken in the same way as gauge is defined for railway tracks. There are hints of rut shape changes reflecting extensive use and or processes such as limestone dissolution, which give insights into their formation histories.

Modeling of Limestone Dissolution for Flue Gas Desulfurization with Novel Implications

Solid-liquid dissolution is a central step in many industrial applications such as pharmaceutical, process engineering, and pollution control. Accurate mathematical models are proposed to improve reactor design and process operations. Analytical methods are significantly beneficial in the case of iterative methods used within experimental investigations. In the present study, a detailed analytical solution for the general case of solid particles dissolving in multiphase chemical reaction systems is presented. In this model, the authors consider a formulation that considers the particles’ shape factor. The general case presented could be utilized within different problems of multiphase flows. These methods could be extended to different cases within the chemical engineering area. Examples are illustrated here in relation to limestone dissolution taking place within the Wet Flue Gas Desulfurization process, where calcium carbonate is dissolving in an acidic environment. The method is the most common used technology to abate SO2 released by fuel combustion. Limestone dissolution plays a major role in the process. Nevertheless, there is a need for improvements in the optimization of the WFGD process for scale-up purposes. The mathematical model has been tested by comparison with experimental data from several mild acidic dissolution assays of sedimentary and metamorphic limestone. We have found that R2 ⊂ 0.92 ± 0.06 from dozens of experiments. This fact verifies the model qualifications in capturing the main drivers of the system.