Contact filter paper technique

Filter paper technique is an alternative to complex testing techniques described in the previous sections. This technique is very simple, cheap, and reasonably accurate for the practical measurement purposes. There are two types of measurement procedures using filter paper technique, viz. contact and non-contact technique, as described in the American Society for Testing and Materials (ASTM) - D5298. The former technique is used for the measurement of matric suction and, alternatively, former technique for total suction measurement. Only the contact filter paper technique is described here for the measurement of matric suction and the other method is explained later sections. The filter paper technique is based on measuring the amount of moisture transfer from the soil sample to an initially dry filter paper when the filter paper is placed in contact with soil sample as shown in Fig. 15.

Fig. 4.15 Illustration of contact filter paper technique (after Lu and Lukos)