While comparable artificial settlements in the Gulf region typically involve extensive backfill on the coast to obtain land for artificial living spaces, the Sabah Al Ahmad Sea City project in the Al Khiran region of Kuwait was designed precisely the other way around. Roughly 300 km of canals were constructed in the desert, and the canals were excavated in the existing soil and then flooded with seawater.
The goals of this project are also monumental in other aspects. The development of this gigantic project, involving billions of dollars in investments, is planned for a construction period totaling 46 years subdivided into ten phases. This project will create living space for up to 250,000 people: a planned settlement that will feature comprehensive infrastructure upon completion including all necessary utilities as well as a whole range of luxurious buildings.
Large buildings are constructed on desert sand by using dynamic soil compaction. This method is particularly suited for increasing the bulk density of non-cohesive, friable soils and loose mixed soils with a low fine aggregate content, which makes it ideal for the subsoil composition in desert regions,
Steffen Fuchsa, Head of the duty-cycle crane division at Bauer Maschinen, said: “And because the pore water is pressed out of the subsoil, in the event of an earthquake there is also a lower risk of soil liquefaction.”
Steel plates weighing a total of 25 tonnes are welded together into structures known as pounders (drop weights). A duty-cycle crane hoists them up into the air and then lets them fall to the ground in a controlled free-fall up to fifteen times, forming a crater as a result of the impact. The kinetic energy emitted on impact penetrates into deeper soil strata and leads to compaction via forced re-packing of the grains.
The hoist functions of the Bauer duty-cycle crane are controlled fully automatically during these work cycles, which means that the equipment operator merely has to enter the desired target parameters into the intelligent machine controls, for example the degree of compaction and the required number of impacts for that purpose. Once the cycle has ended, the equipment moves to the next defined compaction point. This results in a grid of craters. After this initial phase, to ensure compaction over the entire area, the points between the individual craters are worked on with the pounders during the second phase. These overlapping, offset measures followed by backfilling the craters and further compaction ultimately result in a load-bearing construction surface. Currently, six Bauer MC 96 duty-cycle cranes are in use at the construction site.
“In their basic design, our duty-cycle cranes are extremely stable and robust specialist foundation engineering equipment designed for high dynamic loads. This is clear to see in the solid steel construction components of the upper and undercarriages as well as the boom. On the other hand, highly robust and powerful diesel engines are built into Bauer’s MC duty-cycle cranes. The coordinated hydraulic system transfers this power to the hoists. This alone makes Bauer’s duty-cycle cranes the optimal equipment for dynamic soil compaction,” said Steffen.
The challenges posed by dynamic soil compaction for specialist foundation engineering equipment in general, and in this case in particular, are extreme: Due to the sheer magnitude of the ground surface requiring compaction and the tight timeline, the equipment on the project in Kuwait is in operation around the clock. And there are also regional particularities: The temperatures in the equipment during continuous operation in the extreme desert heat make it necessary to ensure cooling for the equipment at all times. Furthermore, there is the omnipresent sand, which penetrates every crack if the sealing is insufficient. To prevent this, various protective devices (e.g. on the cooler) were attached to the duty-cycle cranes in operation.
“One of the major challenges when executing this method is to always roll the rope perfectly up and down into the groove of the hoist, otherwise there is excessive wear on the rope, which causes high costs for the operator,” said Steffen. “Bauer has developed and in some cases even patented several smart solutions for this problem which are unique features of the MC series. The active rope tightening system and the winding assistant make the difference in daily operation compared to competing products.”