Our duty-cycle cranes put to the test

The Sabah Al Ahmad Sea City project is truly impressive! Around Three hundred kilometres of canals were created in the desert for the completely artificial city in the Al Khiran region in Kuwait. The special thing about it: While comparable artificially created settlements in the Gulf region are normally built on land for artificial habitats by means of extensive embankments on the coast, the Sea City project was designed the other way round. The canals were dug into the existing ground and then flooded with seawater. The goals of the project are also impressive in other respects: the development of the gigantic project, which is worth billions, is scheduled to take 46 years to complete and is divided into ten phases. A new home for up to 250,000 people is to be created here, a planned settlement that will have a comprehensive infrastructure including all utilities and a whole series of luxurious prestige buildings once completed. Sabah Al Ahmad Sea City is also the first urban area in Kuwait to be built entirely by the private sector. But how do you build mighty structures on desert sand?

The owner and developer of the project, La'ala Al-Kuwait Real Estate Co., committed to solve this problem. The aim is to prepare the ground of the huge site for development. La’ala Al-Kuwait opted for the dynamic soil compaction method in order to compact the soil appropriately for stable construction.

Dynamic soil compaction is particularly suited for increasing the bulk density of non-cohesive, friable soils and loose mixed soils with a low fine aggregate content, i.e. ideal for desert regions. A heavy drop weight is repeatedly dropped onto the ground from a great height. The kinetic energy emitted on impact penetrates into deeper soil strata and leads to compaction via forced re-packing of the grains. The degree of compaction depends on the mass of the drop weight, the fall weight and the spacing between points.

In practice, steel plates with a total weight of 25 tonnes are welded together to form so-called pounders and pulled upwards using a cable excavator. In a controlled free fall, they are then rammed 9 to 15 times onto the ground, where a crater is formed by the impacts. The devices are then moved on to the next compaction point according to a defined pattern. This creates an impressive grid of craters. After this first phase, the areas between the individual craters are treated with the pounders in a second phase to achieve an even surface compaction. These staggered, overlapping effects ultimately result in an area-wide soil compaction from a point-by-point compaction. Six Bauer MC 96, among others, are currently on site to prove themselves under the difficult conditions.

Although the process itself may appear simple at first glance, the challenges that the dynamic soil compaction method (offered by us as BAUER Dynamic Compaction, BDC) poses for specialist foundation engineering machines in general, and in this case in particular, are extreme: not only does the sheer size of the ground area to be compacted require continuous 24/7 operation with a very tight schedule, but the conditions of the region itself also push the machines to their limits. The temperatures developing in the machine during continuous operation culminate with the external heat of the desert, which makes the necessary, permanently guaranteed cooling of the machines a challenge. The omnipresent sand whirled up on impact (or even just by the wind) penetrates into even the smallest cracks in the appliances if they are insufficiently sealed. The wear and tear on the material caused by the gigantic forces constantly acting on it is enormous.

Bauer has been endeavouring for years to find innovative solutions to the challenges of the process. For example, one of the biggest problems during execution is keeping the excavator's rope, to which the pounder is attached, from jumping over. Bauer addresses this with a unique, patented Rope Tightening System developed especially for this case. A unique selling point of Bauer’s duty cycle cranes. Just as significant: the Active Rope Assistant (ARA) for smoothly winding and unwinding the ropes on the winches in combination with the winch control for MCs, which has also been patented and specifically revised for BDC, and which together ensure smoother braking when winding. Needless to say, the control screen has also been customised for the best possible execution of the BDC process.

Speaking of innovations: When it comes to products such as our special foundation engineering machines, the best insights into potential improvements can still be gained in everyday construction site life. Especially under such challenging extreme conditions. That's why we support our customers on site to achieve the best performance with our devices.

Our MC 96 in combination with a 25t pounder are a well-rehearsed team with optimal performance and optimized material wear. But the BAUER Dynamic Compaction process can be carried out with all of our MCs, from MC 76 to MC 128, and theoretically also with heavier pounders up to 30 tons.