Energy piles are a new innovative renewable energy technology to access and exploit the relative constant temperature of the ground for efficient heating and cooling of buildings. Examples of energy piles include drilled shafts, continuous flight auger (CFA) piles, driven piles, and micropiles. A field test setup was installed at the Virginia Tech Geotechnical Research Facility to study energy piles. The field test consists of a total of five micropiles 25 cm (10 inches) in diameter, four of which were equipped with circulation loops. The test piles extend to a depth of 30.5 meters (100 feet) and are heavily instrumented with strain gauges and temperature sensors. Several observation boreholes were formed around the test piles to monitor ground temperatures. Thermal conductivity tests and field load testing were performed to investigate the behavior of Energy Piles. This paper presents results of the thermal conductivity tests and thermo-mechanical field load test performed as part of this field investigation.
By Karsten Beekhaus, Sander W. Odijk, Rabea Bahlum, Mazin Adnan, Ayman Abdelh Al Nuaimat, Hassan Farhat
The Arab Potash Company, APC, is one of the 10 largest potash producers of the world. The solar ponds at
the Dead Sea, used for the enrichment of the salt content in the brine, are of crucial importance for the first
step in the exploitation of the potassium salt. Targeting at the expansion of production in the since over
50 years utilized facilities, the increase of the brine exploitation capacity, reducing the substantial brine
seepage losses from the ponds, becomes a crucially required measure. In this context, the remediation
measures on the over 11 km long Dyke 1, being a main dyke of the solar ponds system, became inevitable
to reduce the brine losses, prevent further development of sinkholes and cavities and hence assuring the
stability of the dyke.
The highly aggressive environment, the acting hydraulic conditions and the sensitive stratification and nature
of the existing ground represented remarkable challenges for the design, as well as its implementation by
the construction activities. Royal Haskoning developed a solution addressing the challenges above and
targeting at a high sustainability of the executed structure, especially in view of the various geological and
hydrological hazards repeatedly occurring in this Dead Sea region, including sinkholes of several meters by
diameter and depth.
The construction works, consisting of a cut-off wall, with depths reaching down to 31 m, were awarded to
Bauer International FZE, a subsidiary of Bauer Spezialtiefbau GmbH. Upon the execution of the first section
of 4.2 km length, additional sections were subsequently commissioned, also on further dykes, totaling to
about 300,000 m² of cut-off wall.
The specific project conditions, such as utilization of cutter technique for the excavation in Halite rock, the
stability of open trench exposed to hydrostatic pressure of salt-saturated ground water, resulted in
unconventional requirements towards the supporting fluid. The extremely aggressive saline conditions –with
a Dead Sea water density of 1.25 tons/m3; one of the world's saltiest water–, were further a decisive factor
for the definition of the backfill material concept. Despite its clear advantage for construction of cut-off
walls with installed sheet piles, the single-phase system with hardening slurries, fulfilling both functions of
excavation support and cut-off wall backfill material, had to be abandoned in favor of the two-phase system,
to construct a hybrid cut-off wall made of sheet piles and plastic concrete.
Improvements in construction equipment and techniques in recent years have made possible the use of drilled shaft foundations in diameters and lengths not previously considered practical or feasible. Many highway bridge and other structures are now routinely founded on drilled shafts which are 2.5 m to 3.0 m (8 to 12 feet) in diameter and extending over 60 m (200 feet) in depth below grade. There are unique challenges associated with constructing such large and deep cast-in-place foundations and engineers should be aware of the special needs associated with site investigation, construction specifications, material requirements, and quality assurance. This paper outlines a number of special considerations for these foundations, along with strategies that may be employed to improve the reliability and quality of large drilled shaft foundations.
Field Testing Of Energy Piles At Virginia Tech