Confuse between BS1377:1990 Part 6 CL 3.6.8.3

[Dekay]

Refer to Subject, im stil confuse the formula used which is Cv = 0.111 H2/ t90, instead of the normally used formula Cv = 0.848 d2/ t90... Based on wat i could understand is that "H" is refer to the total height but the "d" refer to drainage depth.... for a two way vertical drainage... the "d" is half of the height H.... So by combining this two formulae... the result produce for coefficient of Cv by using total height should be 0.212 instead of 0.111.... Can any1 here give me an answer with detail explanations?

 

[paganel]

Please check “the "d" is half of the height H”, I don't think it is right.H/D should be less than 0.4. Also normally you should check Part 5 instead of Part 6 for the conventional oedometer test even the formula is the same to some extent.