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Engineer's Report on Wall Strength
BACKGROUND: The design of the swimming pool is governed basically by the load condition imposed on the pool when the structure is empty. Generally, hydrostatic pressure is applied when the pool is filled with water and this pressure offsets the lateral earth pressures imposed on the pool wall system. When the pool is empty the lateral earth pressures are by far the most dominant design condition. During construction the lateral earth pressure is increased due to the application of surcharge loads such as machinery used to backfill the pool.
DESIGN CONDITIONS: With the
Thermaform Polystyrene Shell material used, the pool is generally shaped with a number of curves to form the required design shape. Once the computer pre-cut panels are in place, concrete is poured to tie the tops of the panels together
The lateral pressure exerted on the walls of the pool is a function of the soil type into which the pool has been constructed. Generally, the greatest pressures are to be accommodated where the friction angle of the soil is least. The lateral pressure imposed on the wall panels is greater for granule type soils with low clay contents.
LOAD TEST: In accordance
with practically assessing the strength of the empty pool wall system, we decided to carry out a load test on a pool under construction. The pool as shown in Figure 1 was visited on a site in Leeming, Perth,
Western Australia. The pool under construction is shown in the photo on this page.
Figure 1
The soil type into which this pool has been constructed essentially of clean uniform sand having a friction angle of
approximately 30". The pool was loaded using a bobcat excavator machine.
TEST OBSERVATIONS: During the tests it was observed that the pool wall at point 'x' on Figure 1 moved inwards by approximately 10mm. There was no sign of flexural cracking during the test and the deflection of the pool wall at the top was deemed to be elastic. We would note that the test was carried out on the pool shell, which had not been stabilised with a concrete floor.
