Jeffrey A Schaefer | Product tags |

Search Results: “” — Page 1

Jeffrey A. Schaefer, Ph.D., P.E., P.G. and David M. Schaaf, P.E.

In 2005 the U.S. Army Corps of Engineers (USACE) developed and implemented a Screening Portfolio Risk Assessment (SPRA) process for Dam Safety. The screening process considered loading frequency, an engineering rating to estimate a relative probability of failure, and both human life and economic consequences of failure. The results were utilized as a tool to help prioritize funding for dam safety modification projects and required studies. Three multidisciplinary cadres evaluated what was considered the worst 10% of the USACE’s dam projects in 2005 and the next worst 10% in 2006. The dams evaluated included flood control, navigation, and multi-purpose dams. Approximately seventy facilities were evaluated each year.

As a result of the aging of the USACE’s dam portfolio and the state of the art at the time of design and construction (mostly 1940’s-50’s), significant dam safety deficiencies exist at many USACE dams. This paper summarizes the major deficiencies identified from the SPRA process. Examples, including foundation seepage, karst development, embankment stability, gate deterioration, liquefiable foundations, and inadequate spillway capacity are provided along with discussion on which deficiencies contribute the greatest risk.

Now showing all 3 search results

$15.00

2006 Papers

2006 – A Summary Of Major Dam Safety Deficiencies Identified By The Initial U.S. Army Corps Of Engineers’ Screening Portfolio Risk Assessment Program
Learn more
Learn more

Jeffrey A. Schaefer, Ph.D., P.E., P.G. and David M. Schaaf, P.E.

In 2005 the U.S. Army Corps of Engineers (USACE) developed and implemented a Screening Portfolio Risk Assessment (SPRA) process for Dam Safety. The screening process considered loading frequency, an engineering rating to estimate a relative probability of failure, and both human life and economic consequences of failure. The results were utilized as a tool to help prioritize funding for dam safety modification projects and required studies. Three multidisciplinary cadres evaluated what was considered the worst 10% of the USACE’s dam projects in 2005 and the next worst 10% in 2006. The dams evaluated included flood control, navigation, and multi-purpose dams. Approximately seventy facilities were evaluated each year.

As a result of the aging of the USACE’s dam portfolio and the state of the art at the time of design and construction (mostly 1940’s-50’s), significant dam safety deficiencies exist at many USACE dams. This paper summarizes the major deficiencies identified from the SPRA process. Examples, including foundation seepage, karst development, embankment stability, gate deterioration, liquefiable foundations, and inadequate spillway capacity are provided along with discussion on which deficiencies contribute the greatest risk.
Learn more
$15.00

2008 Papers

2008 – Dams on Karst foundations risk assessment and remediation
Learn more
Learn more

Jeffrey A. Schaefer

Abstract: The U.S. Army Corps of Engineers (USACE) has numerous dams built on limestone foundations that are susceptible to solutioning (karst). Significant dam safety issues related to the karst foundation have developed in many of these projects. Screening risk assessments of the USACE portfolio of dams has shown that defects related to karst foundations is one of the largest contributors to our risk. To better evaluate this risk, a method to estimate the probability of failure from piping into karst foundations has been developed by team of experts from the University of New South Wales, URS, the US Bureau of Reclamation, the US Army Corps of Engineers. This paper summarizes the major failure modes associated with dams on karst foundations and the methodology developed to perform risk analysis. A summary of USACE case histories with karst foundation issues and recent projects to remediate the foundations are also included.

KEYWORDS: Dam, Seepage, Karst, Solution Feature, Risk
Learn more
$15.00

2008 Papers

2008 – An overview of risk assessment tools for US Army Corps of Engineers dams
Learn more
Learn more

David M Schaaf, Jeffrey A Schaefer, Rick W Schultz, Jason T Needham

Abstract: As one of the main federal agencies with responsibility to build, operate, and maintain large dams in the United States, the US Army Corps of Engineers (USACE) is developing a risk based framework to better manage their portfolio of 600+ dams in terms of risk management and prioritization of funding. A key element to this effort is the development of risk-based analytical tools to evaluate primary features for applicable failure modes. These are used in conjunction with loading and consequence modules to assess the overall risk associated with the dam in terms of lives and economic damages. The focus of this paper is on the engineering analysis modules used to generate fragility curves for dam features.

The analysis modules are broken into three main categories by engineering discipline: geotechnical, structural, and mechanical/electrical. The risk based assessment tools associated with geotechnical failure modes include Seepage & Piping, Embankment Stability, Seismic Performance, and Erosion of Unlined Spillways. The structural assessment tools include Concrete Monolith Stability, Spillway Gates, Scour of Concrete Lined Spillways, Spillway Training Wall Stability, Performance of Pipes through Dams, Hydropower Superstructures and Intake Towers. The mechanical and electrical are primarily focused on the performance of machinery used to operate dam gates.

This paper gives a broad overview of the main characteristics and methods used for each of these analysis tools. Some of the modules use historical performance to establish failure rates, while others are more analytically based. The context of each within the framework of the overall risk assessment effort of USACE dams is covered.

Keywords: risk based analytical tools, fragility curves, risk assessment, US. Army Corps of Engineers, portfolio, dams.
Learn more

All Products

Search Results: “” — Page 1