اثرات اندركنش خاك- اتمسفر در محل قرارگيري خط فرياتيك و پايداري سدهاي باطله (مطالعه‌ي موردي: سد باطله‌ي مس سرچشمه)

Effects of Soil-Atmosphere Interaction on the Phreatic Surface and Stability of Tailing Dams (Case Study: Sarcheshmeh Tailing Dam)

اين نوشتار به بررسي پايداري سازه‌هاي خاكي تحت تاثير اثرات اندركنش خاك- اتمسفر مي‌پردازد. اندركنش خاك- اتمسفر در قالب پديده‌هاي مختلف بر محل سطح فرياتيك در بدنه‌ي سازه‌هاي خاكي نظير سدهاي باطله و وضعيت پايداري آنها تاثير مي‌گذارد. در اين پژوهش، پس از شناسايي مكانيزم‌ها و استخراج روابط حاكم بر آنها، تغييرات تراز خط فرياتيك در بدنه‌ي سازه‌هاي خاكي تعيين و پايداري اين سازه‌ها مورد بررسي قرار گرفته است. نتايج به‌دست‌آمده نشان مي‌دهد هر چه عوامل اتمسفريك به تغيير بيشتري در محل خط فرياتيك منجر شوند، وضعيت پايداري سازه بيشتر دست‌خوش تغيير خواهد شد. در ميان عوامل مطالعه‌شده در اين پژوهش، ميزان تاثير پديده‌هاي مويينگي و تبخير در پايداري بيشتر بوده است. در انتهاي نوشتار، تاثير شرايط اتمسفريك و اندركنش خاك- اتمسفر در پايداري سد باطله‌ي معدن مس سرچشمه‌ي كرمان مورد بررسي قرار گرفته است.

Positioning of the phreatic surface in a dam body plays a critical role in the stability of tailing dams. Soil-atmosphere interaction effects, such as precipitation, runoff, interception, infiltration, and evaporation, on the one hand, and unsaturated soil effects, such as capillary rise, on the other, cause significant changes in the situation of the phreatic surface. In this paper, first, different mechanisms that affect the phreatic line level in the tailing dams and their corresponding equations are studied, and a computer program is developed for calculating the fluctuations of the phreatic line. Then, for evaluating the usefulness of the program in real time problems, the stability of “Sarcheshmeh” copper mine tailing dam in Rafsanjan city, Iran, has been studied. Plaxis software Ver.8.0 has been used for modeling this tailing dam. Necessary parameters for modeling this dam have been obtained from the results of different laboratory tests on tailing materials, and information available from synoptic stations of the meteorological organization of Iran in the area. After determining the amount of change in the phreatic level for a special period of time, the stability of the dam was studied, based on calculating the factor of safety under different conditions. The results show that by constructing new dikes, the safety factor decreases. Also, the results show that those parameters that increase the phreatic level reduce the safety factor, and the stability of the tailing dam will be threatened. Among different parameters affecting the phreatic level, capillary rise was found to be the most significant factor in regard to tailing dam stability when constructed in arid areas.