The Standard Vacuum Oil Company's new 7,000,000 refinery at Wentworth, Durban, which has boon in operation since 1953, is located on the Bluff and near the Wentworth peat bog. At the refinery site the foundation material consists briefly of sand to a 50 foot depth, then clay to 70 feet and then Band which has been proved to 120 feet depth. Due to the small differential settlement requirements it was decided to found the major items of plant on long piles taken down 100 feet and it is believed that these are the longest piles which have been constructed in South Africa. In certain instances piles had to be jetted in order to facilitate the driving through the top horizon of sand.
During 1955 it became apparent that a new problem in foundation engineering faced civil engineers in South Africa. To the heaving conditions which are now fairly well recognised must be added a new condition associated with what is believed to be a collapse of certain sandy soils when under load and when inundated. The problem appears to be encountered mainly with sands resulting from the Kalahari era and with colluvial Bands and silts in the upper strata of typical South African soil profiles.1 The moisture content of the subsoil at time of construction is also a very important factor.