Max Line Pressure for a Thrust Block (AWWA M41)
The inverse of the thrust-block tile: the highest test/surge pressure a thrust block of a given bearing-face area restrains at a bend, P = Ab x soil / (2 A sin(theta/2)). A 4.13 ft^2 block on an 8 in main (OD 8.625) at a 90-degree bend in 2,000 psf soil holds about 100 psi. Answers 'how much pressure can this block take' instead of the area from a set pressure; compare against the test/surge pressure. Checks the bearing face only; the engineer of record governs.
Formula and source
A = (pi/4) OD^2; max_thrust = bearing_area x soil; max_pressure = max_thrust / (2 A sin(theta/2)). The inverse of Ab = 2 P A sin(theta/2) / soil.
The AWWA M41 thrust-block resultant-thrust and bearing-area method for a pipe bend, by name, solved for the pressure.
Audience
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Posture
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