This paper presents the geomechanics of the upper Miocene rock foundation, which included estimating the rock mass properties and evaluating rock foundation behavior for the rehabilitation of the 50 year old Hamidieh dam. The geomechanical data were used as input parameters for the analysis of the foundation stability and the design of the remedial programs and In addition, a seepage analysis of the foundation rock was carried out. The stability analysis of the dam against sliding and uplift pressure was assessed using the equilibrium analysis for the proposed compound remedial programs. After careful analysis of several design alternatives, a solution involving 96 relief wells in two rows, rip rap protection was selected for implementation, whereby the dam would be safe for future operation.
The Hamidieh Dam was constructed about 50 years ago (1957) on the Karkheh River in southwest Iran (Fig.1). The dam is 192 m in length and has 19 spillways, 10 gates and one fishway and is one of the oldest dams in Iran (Fig. 2). This concrete gravity dam has a maximum head of 9 m (in NWL condition the maximum head is 4.5m) and supplies irrigation water to some 20,000 ha of downstream land by way of two side channels. In 2002, with construction of the main Karkheh Dam upstream, 149,000 ha of land should be irrigated gravitationally by the Hamidieh Dam. Due to the important role of this dam, it has been deemed necessary to perform a stability analysis and determine a remediation plan for the dam. The Hamidieh Dam was constructed on the northeast flank of the Zeinolabbas anticline on the Aghajari geological formation which consists of a sequence of sandstone, siltstone and marlstone.