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Volume 3, Issue 1 (11-2009)

In this study, seepage phenomena through the left abutment of Marun dam are investigated. The Marun dam is a 170 m high rock fill dam, which regulates the waters of the Marun River, serves power generation, and flood control and provides irrigation needs. The dam site lies in the Zagros Mountains of southwest Iran. This region presents continuous series of mainly karstic limestone, marl, shale and gypsum ranging in age from Cretaceous to Pliocene. The region has subsequently been folded and faulted. All underground excavations are sited in the left abutment. The spacing of the diversion tunnels and pressure tunnel is considered to be acceptable, meaning relatively short, thus requiring 2 row grouting curtain into both embankments. Prior the reservoir impoundment, the concrete plug was constructed into the middle section of second diversion tunnel. Upstream section of tunnel was not concreted. During the first reservoir impounding, the old karst channels along ‘Vuggy Zone’ cut by the second diversion tunnel were reactivated and leakage occurred. The total amount of water leakage through the left bank of Marun dam was about. The unlined second diversion tunnel had a key role in connecting reservoir with karst conduit system. On the basis of detailed engineering geological analysis, the concept of remedial works was carried out. The main points of this concept are one of row grout curtain extension up to the section with shaly interbeds declared as watertight Asmari sequence (close to the watertight Pabdeh formation) and plugging of accessible section of main karst channel by concrete. In order to determine the seepage direction and karstification pattern, solubility studies were done. Also pinhole, XRD and XRF tests were carried out. The major joint system and interbedding cracks have predominant role in karst evolution process. Hydrogeological role of joints, perpendicu-lar to geological structure, is not negligible. As a result of these studies, seepage paths have been identified in the karstic limestone in the left abutment of the dam.
B B, M Kh, ,
Volume 4, Issue 1 (11-2010)

Gotvand dam reservoir with over 90 km length is surrounded by Gachsaran, Mishan, Aghajari and Bakhtiari formations. The noticeable point in the dam reservoir is the presence of Gachsaran Formation that is composed of considerable volume of salt located  4 km upstream of dam. Salinity of dam water due to dissolution of salt in reservoir water can cause serious environmental problems. In addition to direct dissolution of salt in contact with reservoir water, slope instability can also influence on this process. Probable sliding in salty layers of slopes will insert a significant volume of salt in contact with reservoir water in a short time. In order to study the land-sliding process in reservoir area and also analysis of the effect of dissolution of salty layers on sliding, characteristics of dominant material engineering of mass constituent were defined by rock mechanics experiments. Then the results of performed tests on rock samples and GSI method were used to estimate the engineering parameters of rock mass. To investigate the land-sliding process in reservoir area and also the effect of dissolution of salty layers on sliding, some salt samples were transferred to the laboratory. Using circulation method, solubility of those samples were examined in different conditions. The results were generalized to the reservoir condition. Eventually, slope stability were analyzed by modeling with SLIDE software, considering different levels of reservoir water, influence of dissolution of salty layers. The obtained results indicate that slidings in reservoir area are mostly shallow and are caused by dissolution of salty layer.

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