Laboratory simulation of karst development in carbonate rocks containing insoluble substances: a case study from west Iran

摘要

Karstification in carbonate rocks has caused numerous serious problems during construction projects, such as water escaping from beneath dams and reservoirs, dam foundation aging, and karst collapses. Identifying the main factors involved in carbonate dissolution processes and/or their dissolution potential could help with the development of practical approaches to common hazards associated with dam sites. Therefore, collecting data on dissolution potential and rate could be a very useful task. In this regard, the current study attempted to evaluate the rate of karst development in carbonate rocks with insoluble substances at a dam site in west Iran by performing simulated tests in the laboratory. In order to calculate the rate of chemical dissolution in the right abutment of the Patagh Dam site, we utilized appropriate equipment running in a closed system. A set of simulated laboratory experiments were conducted under predefined test conditions. Subsequently, the maximum EC change (82 mu S/cm) was recorded at pH 6.5. Results also illustrated that both chemical dissolution and mechanical deterioration concurrently affected the weight reduction of the tested specimens. In addition, whenever chemical dissolution took place in a site with impure carbonates, the rate of physical deterioration increased. However, in the absence of chemical dissolution, the ratio of the rate of physical deterioration to the total weight of the samples remained virtually constant. Furthermore, due to the sensitivity of carbonate rocks to changes in pH, the ratio of the weight loss caused by physical deterioration to the total weight loss of the samples increased from 42 to 81 % as the alkalinity of the flowing water increased. The results show a relationship between chemical dissolution and mechanical deterioration, leading in turn to enhanced karst development rates.