Rehabilitation of Temporary Composite Dams (Case Study: Mared Soil-Sheet Pile Dam)

Flow rate of Karun river, which is the longest and largest river in Iran, decreased from 600 to 100 m³/s in average, due to the drought in early 2008. This reduction caused water from Persian Gulf to advance farup-river and reach a raw water supply basin and increase water electrical conductivity (EC) to 5,000 μmoh/cm. A temporary dam constructed from soil-sheet pile was installed to prevent salty water progress to the water supply location. Heavy rain fall and flooding with a flow rate of 1,000 m³/s destroyed one-third of the dam in November 2008 and therefore, the lives of nearly 300,000 people were in danger due to water shortcoming. In this paper a new and innovative method for repairing the aforementioned dam is presented considering constraints such as type of dam destruction, limited time and cost, and other operating limitations. In this method, the damaged section of the dam was restored by composite geo-box piles. The piles were installed in two rows against the water to create a corridor and then the corridor was filled with soil geo-boxes. Based on the seepage and overturning analysis, and considering implementation conditions, the geometry of proposed method was selected. After successful implementation of the plan, the dam was restored and consequently the EC of the water was reduced to 1,800 μmoh/cm and raw water quality improved significantly in <2 months with minimum cost. It was finally realized that the soil erosion inside the cells was reduced; the bed was stabilized and its integrity over the dynamic loads was sustained. Therefore, it can be said that there is a significant uniformity between the fixed part and the existing structure of the dam. It can be concluded that this method of rehabilitation is an innovative and fast method to fix the damaged dams with minimum cost.