Long-term deformation analysis of Masjed-Soleyman rockfill dam (Iran): results based on terrestrial geodetic data

Abstract

In this research, the post-construction movement of the Masjed-Soleyman dam in southwest Iran was investigated using 15 years of terrestrial geodetic measurements between 2000 and 2015. The stability analysis of the dam body was assessed using the settlement index (SI) criterion. Moreover, a relaxation model was developed for the prediction of deformation in time. The results show that between 2000 and 2015, the middle part of the crest (382.0 m) experienced the highest settlement of about 3.5 m, equivalent to about 2 % of the dam height. For the downstream slope, the middle part of the dam body at 350 m shows the maximum cumulative settlement of about 1.2 m in 15 years. The maximum cumulative horizontal displacement belonged to the middle part of the downstream slope, reaching about 1.4 m. The points located near the side staddles experienced smaller horizontal and vertical movements; the maximum cumulative vertical and horizontal displacements for side points of the crest were about 1 m and 0.7 m, respectively. The stability analysis using the settlement index shows that the points on the downstream embankment have the normal values of settlement index (i.e., 0.02) during the examination, and thus, their settlement could be considered as creep or secondary consolidation. However, the points located in the middle part of the crest exhibit a settlement index that exceeds the instability threshold. The relaxation model that developed in this study suggests that except for some points located on the bottom part of the downstream slope of the embankment, the settlement of the other points will continue for the next few years, even after 30 years of the dam operation. However, the maximum rate of deformations would decrease and reach from 25 cm/yr for the first 15 years of dam operation to 10 cm/yr in the 30th year of operation.