Wall Forms & Hydrostatic Pressure Paradox Pascals Law

[SLPSTRUCT007]

On a wall form with varying height and a “Bulkhead Lid” I know that the pressure at 1 and pressure at 2 must equal each other, due to the hydrostatic paradox (Pascals law), assuming full liquid head. My question is what happens if this “Bulkhead Lid” is removed and the concrete is exposed?

Does the hydrostatic paradox still apply or is the pressure at point 2 something lower than the pressure at point 1. See the snippet below for reference.

 

[CJLCivilStruct]

If the bulkhead is removed then the surface at point 2 is free to air so P must equal 0 - that's my understanding anyway.

Also, worth noting that concrete pressures are not fully hydro static - refer to CIRIA 108.

 

[rb1957]

if you remove the lid then the pressure at 2 is not equal to the pressure at 1, as the head of stuff above 2 is less than 1. no?