Abstract:
The fluid loss test using the American petroleum institute (API) fluid loss cell is a powerful test for assessing the behaviour of particulate grouts but the results from the test are seldom fully utilized. Currently if fluid loss is specified or reported the figure quoted will be the volume of filtrate in ml after 30 minutes filtration under a pressure of 100 psi. Occasionally, as a refinement, a pressure filtration coefficient may be reported. As currently defined the pressure filtration coefficient ??? is: ??? = Volume of fluid expelled, ? ?Initial volume of sample x Test time, ??/? ? ? Unfortunately this definition fails to recognise that for a given fluid and test conditions, ?/??/? is a constant independent of the initial volume of the sample (provided allowance is made for any initial fluid loss, which it will be shown is a separate issue). It follows that including the initial volume in the definition of ??? will lead to inconsistencies unless this volume is fixed. In this respect it is noted that some authors require that a fixed volume of 400 ml of grout is used in the API test cell so that: ? = ??? ??? ??/? which hides the true significance of ??? and renders it no more than a reference parameter. It is also noted that some specifications require that the total volume of fluid expelled is recorded. A parameter of this type is useful if properly defined and determined The paper will demonstrate that the tests should be analysed in terms of two simple parameters, a revised filtration parameter and a cake thickness development parameter. It will then go on to show how filtration behaviour can be coupled with soil permeability to identify overall in-situ grout filtration behaviour.