Thermal Energy In Geotechnical Engineering

Associate Professor John McCartney OPTIMAL DAMAGE DETECTION AND PROGNOSIS VIA ULTRASONIC SCATTERING

Although geothermal heat exchange is a well- understood approach to sustainably heat and cool buildings, it often comes with high up- front installation cost. Professor McCartney’s research in geotechnical engineering seeks to understand ways that geotechnical engineering infrastructure can be used for geothermal heat exchange or storage, in part to reduce installation costs but also to pursue opportunities to use heat to improve the strength or sti ness of soils, or to achieve other objectives such as subsurface contaminant remediation. A major NSF-sponsored initiative has been the construction of a full-scale soil-borehole thermal energy storage system at Englekirk, which operates circulating water heated by solar thermal panels on the surface through an array of closed-loop heat exchangers embedded in 50 ft-deep boreholes in the ground. In this way, heat generated during summer days can be stored in the ground until it is needed later for community- scale heating. Innovative aspects of this project include consideration of multiphase ow processes in the soil above the water table to positively a ect heat transfer and storage. These multiphase ow processes are also considered in another NSF-sponsored project focused on thermal improvement of unsaturated soils reinforced with geosynthetics, which has involved development of di erent laboratory tests to measure e ects of heat on soil properties. Professor McCartney is also actively using UCSD’s 50 g-ton geotechnical centrifuge to evaluate the pullout capacity of o shore piles in clay and to evaluate soil-structure interaction in energy piles in soft clay. Other ongoing geotechnical projects include the use of the Powell laboratory shaking table to investigate the seismic response of geosynthetic-reinforced wall bridge abutments for Caltrans, use of a large-scale direct/simple shear box to evaluate the shearing properties of tire- derived aggregates for CalRecycle, and development of new light-weight laminar containers for the centrifuge shaking table.

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