Seite - 1421 - in Book of Full Papers - Symposium Hydro Engineering

of the ASCE Research Conference of Shear Strength of Cohesive Soils, Boulder, CO, pp. 503–532. [8] Boutrup, E., and Lovell, C. W. (1980). Searching techniques in slope stability analysis, Engineering Geology, 16(1), 51–61. [9] Bray, J., and Travasarou, T. (2009). Pseudostatic coefficient for use in simplified seismic slope stability evaluation, Journal of Geotechnical and Geoenvironmental Engineering, 135(9), 1336–1340. SUMMARY This paper presents the results of slope stability analysis at the right and left bank of the spillway in Gelevand dam which is a broad- crested spillway by assuming 739 m.a.s.l. As the dam crest elevation, the width of channel trench will be almost 66 m to discharge the 10,000-yr flood. Based on the design criteria, large spillway channel should be located at the toe of the right and left abutment which will require a special design for the excavation of berms at Neogene era in order to reach a stable slope. To evaluate the strength parameters of fine-grained materials at spillway area, laboratory test were carried out. According to the strength parameters resulted from lab, the stability of trenches slope of the spillway channel was analyzed. Base on the results, to ensure the stability of spillway trenches, the slopes should be excavated with a gentle slope. Considering the geometry of the current slope and analysis results, a width of 80 meters for approach channel could not be achieved at the level of 730 m.a.s.l. Therefore, to meet the desired width for spillway channel, excavating should be implemented with a steeper slope that this is not possible due to the instability of fine-grained material of the Neogene formation at spillway area, unless by using soil improvement methods for fine grained material. In regards to above mentioned conditions, the cost of the project will be increased. Indeed, considering the nature of the Neogenetic fine, it was decided that "in-situ" tests should be perform to obtain the fine-grained material properties at the spillway area. Based on the strength parameters results obtained from "in-situ" tests again the stability of trenches elaborated. KEYWORDS Spillway, In Situ test, Slope stability, Gelevard, CFRD Dam, Approach channel 1421