Suction-Moisture Content Calibration of Filter Papers from Different Boxes
The filter paper method is probably the simplest of the methods available for estimating the suction of a clay soil. The method measures soil suction indirectly by simply measuring the moisture content of a filter paper having been brought to the same suction as the soil. Calibration of representative specimens of the filter paper over a range of known suctions defines the suction-moisture content characteristic of the material. The calibration must be carried out in a closely temperature-controlled environment using various apparatus depending on the particular level of suction. There have been a number of impediments to the wider application of the filter paper method. One of these is the need to have access to a closely temperature-controlled laboratory with a range of specialist calibration apparatus. This difficulty has been exacerbated by the belief that to account for the possible variability of filter papers between boxes, even from the same production batch, representative specimens from each box require separate calibration. Based on the results of careful calibration and subsequent analysis, it appears that, provided the boxes are all from the same production batch and are purchased from the same outlet at the same time, the calibration of only one box is necessary.