High capacity multistrand rock anchors have been installed through the main arch and one thrust block of Stewart Mountain Dam, Arizona, to ensure the stability of the dam and foundation during extreme seismic events. This paper describes a full-scale test program performed beforehand to verify anchor design and performance assumptions.
Stewart Mountain Dam is a 65-m-high arch structure, with gravity thrust blocks and abutment sections (Figure 1). The dam was completed in 1930 on the Salt River approximately 40 miles northeast of Phoenix, Arizona. As part of dam safety modifications, 84 high capacity rock anchors were installed through the main arch and left thrust block to ensure stability of the dam and foundation during extreme seismic events. Concrete blockouts for the anchors had been constructed as part of a separate contract for other modifications, so there was no chance to relocate anchor positions in the event of initial anchor failure. Therefore, the contract specifications required a full-scale test program to verify that the design of the bond length would provide an adequate margin of safety in resisting the tension applied to the anchors. Additional testing and monitoring, described in section 3, were performed to maximize information gained from the tests, and to aid in better understanding the anchor behavior and performance. This paper describes the anchor test program and its results.