SAFETY EVALUATION OF ABBASABAD HISTORICAL MASONRY DAM

Abbasabad 400 year old masonry dam located in north eastern Iran near Behshahr city is one of the major historical hydraulic structures with current height of 18 meter and crest length of about 200 meters and crest width of 7 meter with a spillway in the middle of the dam. In this paper the results of safety evaluation study on this dam are presented and discussed. Some experimental programs are conducted to assess the current status of the dam and foundation materials and seepage rate and the results have been discussed to obtain appropriate parameters for further numerical modeling. On the other hand some pilot experimental studies were conducted to obtain the most practical and efficient grouting procedure for seepage control and local strengthening. Several grouting pattern were tested and the results were checked using lab experiments. These block patterns were used to find the most appropriate depth and distances of grouting holes. Various numerical analyses have then been performed to monitor the current status of the dam considering overall and local stability, water tightness and stress and strain and crack distribution through dam body while adopting the experimental results. These analyses have been performed using general purpose finite element program. Based on the seismicity investigations the effect of earthquake has also been considered to assess the local and global stability of the dam. The results showed that the dam cannot resist seismic loads based on the defined factors of safety. Based on the experimental and numerical results, possible methods of stabilization, strengthening and seepage control are proposed. Considering the historical value and tourist attraction issues of the dam and also the economical issues, the best methods of rehabilitation have then been selected through detail discussion. Finally the results are presented through graphical figures and site photos. The results of these project will be used for rehabilitation and strengthening phase for the dam.