Evolving Thermal Grouts Aid Growth of Underground Power Transmission Lines

By Jeff Griffin, Senior Editor | December 2010 Vol. 65 No. 12

From the installation viewpoint,” Parmar explained, “flow and pumpability are related and are the governing factors for limiting pumping pressure and rate of pumping. Various other factors such as the total distance to be pumped, size of the casing, number of ducts, spacers, change in elevation, etc., must be taken into account because they all contribute to the total resistance to pumping. From the grout installer's view-point, flow and pumpability are of primary importance for any project.”

For most civil engineering applications only the flow and strength may be of interest, Parmar added.

“In order to specify/spec a thermal grout the engineer must have a clear understanding of what is required (material), why is it required (performance) and how it should be installed (process). Design of the thermal grout must be conducted by 'experienced' person; taking into consideration the thermal, mechanical and project specific requirements. The material supplier and installer must be equally knowledgeable and experienced to understand the requirements and means of delivering them. A successful demonstration of the material and the process prior to the actual installation will gain the confidence of the owners and consulting engineers.”

Industry sources expect the number of projects including underground power transmission lines to steadily increase. Buried 230 kV lines are not uncommon in the United States, and several 345 kV have been made. In Asia and Europe, transmission networks are in operations that contain 400 kV and 500 kV underground segments.

“One thing I can say for certain,” said Dickes, “the amount of knowledge developed in thermal grouting construction technology has grown by orders of magnitude over the last several years. Owners and engineers need to know that long distance thermal grouting of underground casings has been performed successfully in the United States.”

Dickes is participating in planning of a project now that will include 3,000 feet of 230 kV underground transmission lines in an uncased bore. Geotherm and Constellation Group have developed the specified thermal grout for this project during the summer of 2010.

Constellation Group LLC, (410) 484 0672; www.cgllc.us

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