It is suitable for measuring the water permeability of flat drainage materials in geosynthetics of railway engineering. In the state of laminar flow, a certain normal load is applied to the surface of the sample, and a certain head difference is applied to the two ends of the sample, and the water flow through the two ends of the sample within a certain period of time is measured.

Standard Q/CR549.6-2017 China Railway Corporation Enterprise Standard Appendix C specification requirements.