Errors, Misunderstandings, and Mistakes in Remedial Grouting Projects for Dams

Abstract

The technical revolution in remedial grouting for dams is well into its second decade of practice in the U.S. Technical papers, textbooks and Government guidelines have been published detailing what is now considered the state of that practice. Many large projects have been undertaken in very challenging technical and dam safety situations, and experiences have been shared. However, the authors still find that not all participants in this field truly appreciate the details and subtleties of our current practice and certain poor practices from earlier decades are beginning to resurface. This paper highlights some of these issues, and offers plain guidance on:  Design Aspects (such as the number of grout hole rows and maximum safe water testing and grouting pressures.  Construction Details (such as the true value of an engineered, concrete working platform, the use of Water-Powered Down-the-Hole Hammers, the difference between Refusal and Closure, and the correct placement of standpipes for epikarst treatment).  Analytical Details (the difference between real and Apparent Lugeon values, and their relation to residual permeability).  QA/QC Aspects (such as tolerable ranges for fluid grout properties, and the necessity to have a functional DMS system).  Dam Safety Monitoring (such as the need for Joint Instrumentation Monitoring