Foundation Investigations for Rehabilitation

摘要

The foundation of a structure may be a concern due to historical occurrences, PFMA findingsrnand/or part of the rehabilitation plan for an aging dam. The need to obtain sufficient technicalrnfoundation information should be balanced with economic considerations.rnThis paper will discuss how foundation investigations more than offset the costs for the selectedrnimprovement. In addition to providing design information, the investigations identified criticalrnelements for construction mitigation measures. Some of the projects that will be discussed are:rn1. A powerhouse on a granular soil foundation that required lengthening the under seepagernpath by installing sheet piling. Because there was a concern that abnormal settlement ofrnthe structure might occur by installing the sheet piling, the foundation was furtherrnmonitored and underpinned with grout.rn2. An ambursen dam on a sandstone foundation that required the installation of post tensionrnanchors tied to the buttresses. There was a concern that there were probably granularrnlenses in the sandstone that might affect the anchor design and could result in artesianrnconditions during the anchor installations. Thus, the mechanisms and cost to dewaterrnduring construction were very important.rn3. The major replacement of generation equipment in a powerhouse that was located on arnsandstone foundation. The project required significant dewatering and concrete removals,rnwhich affected stability. The potential uplift pressures needed to be quantified andrnmitigation plans developed for construction dewatering.rnFor these projects, instrumentation was left in place as part of the Surveillance Monitoring Plan.rnIt provides ongoing information on potential foundation problems that could impact the projectrnstability.