Abstract:
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.