Cabins have just been installed on an asphalt car park. The portable cabins weigh 4000 kg with 4 no. 300 mm square spreaders under each foot.

The car park is constructed from:
1" thick rolled asphalt
2" thick bitumen macadam
6" thick granular subbase
well compacted ground

The effective pressure on the asphalt is:
4000 kg = 40 kN / (4 × 0.3²) = 111 kN/m²

The question is whether this load is likely to cause permanent deformation of the asphalt leading to problems with ponding of water in the future.

I know this is a complicated question depending on the semi-solid nature of the asphalt and its rheological characteristics. The temperature for the duration of the portable cabins is not expected to exceed 30°C. The cabins are expected to be in place for approximately a month.

Any guidance, rules of thumb or a point in the right direction would be appreciated.