ADDRESSING AAR STABILITY CONCERNS AT SANTEETLAH DAM

摘要

The Santeetlah Development is one of four dams which comprise the Tapoco Projectowned and operated by Alcoa Power Generating Inc. (APGI). The SanteetlahDevelopment was originally constructed during the period 1926-1928 with modificationsthroughout its operating history. The project consists of an integral intake section, anarch section spanning between the massive left and right thrust blocks, and left and rightwing wall non-overflow gravity sections. There exists evidence of continued alkaliaggregatereactivity (AAR) at the dam. Slots were cut in the right thrust block and leftwing wall in 1950, in the left wing wall in 1999 and in the right thrust block in 2003 torelieve stresses from AAR growth.A potential failure mode identified as part of the project’s PFMA session was AARinduced lifting of the thrust blocks resulting in instability and dam failure. To addressthese concerns, a finite element model (FEM) was created to analyze the effects of AARinduced growth on the stability of the dam.The concrete expansion caused by AAR was modeled in the finite element analysis as athermal load. In addition to the AAR loads, the FEM was used to evaluate the effect ofgravity, hydrostatic, uplift and thermal loads. The AAR growth used in the model wascalibrated to produce results matching field measured dam displacements. The measuredfield stresses were also considered in the calibration effort. Non-linear contact elementswere modeled at the base of the dam and at joints between the wing wall, thrust block andarch. The factor of safety was calculated by lowering the friction angle at the base of thedam until the dam slid downstream. This friction angle was then compared to the frictionangle of the rock to concrete contact to determine the factor of safety.The paper will discuss use of this model to evaluate stability of the arch section and thrustblocks with and without reactivity, as well as the model development work that wasneeded to match the field measured displacements and stresses.