Construction of 6 meter deep pit in unstable saturated sand with water table at 1.2 meters below ground level. No worries, we have the solutions as these photos show.
Building an upside down pit. Construct the top 3 meters before you excavate the bottom 3 meters.
No sign of water in pit, the de-watering working fine. After base is poured and cured, the pumps are turned off and the pit was water tight.