GEOLOGIC FACTORS INFLUENCING DAM FOUNDATION FAILURE MODES

摘要

According to the International Commission on Large Dams (ICOLD), approximately 70 percent of concrete dam failures can be attributed to dam foundation issues, either geologically or geotechnically based. In 1929, Terzaghi wrote (regarding the [then] current practice of dam foundation evaluation), "To avoid the shortcomings associated with present practice requires first of all expert translation of the findings of the geologist into physical and mechanical terms. Next it requires the evaluation of the most unfavorable mechanical possibilities which would be expected under the existing geologic conditions; and finally to assume for the design of the structure the most unfavorable possibilities. These mental operations represent by far the most important, most difficult, and most neglected tasks in the field of dam foundations." Unfortunately, the shortcomings referred to by Dr. Terzaghi are still evident in today's practice - more than 70 years after his statement was first penned! Dam incidents and failures continue to occur, albeit at a lower frequency of occurrence. Many of these failures are directly attributed to a lack of knowledge and understanding of site geologic conditions and neglect of a critical assessment of potential dam foundation failure modes. A general discussion of some of the more common geologic features that should be considered in a focused evaluation of potential foundation-related failure modes is presented.