In-situ permeability tests

Our clients are frequently confronted with new requirements of municipalities and water management authorities to disconnect the rainwater from the sewer system and to allow precipitation infiltrate the soil. Furthermore, in the redevelopment of existing and the development of new residential and/or industrial areas, insight in hydrogeologic behaviour and the permeability factors of the soil layers is important in regards to design heights, ponds, wadis (water drainage through infiltration) and drainage systems.

For such projects, MOS Grondmechanica increasingly uses in-situ tests with which the soil constants, such as water permeability (both horizontal and vertical), the infiltration speed and capacity can be determined. These constants are determined using the following tests; ring infiltration test, constant head K-sat and Falling head.

For the determination of the permeability factor from the ground level or in the unsaturated top layers, the in-situ “ring infiltration test” is applied. With this measurement, the (vertical) infiltration capacity of the soil (for example, after heavy rainfall) is determined.

For measuring the permeability in the unsaturated zone, the “constant head K-Sat” measuring instrument (compact constant head permeameter) is used. With this measurement the horizontal permeability factor of the soil levels located above the ground water are determined.

For measurements below the prevalent ground water level, the “Falling-Head” test (reverse Hooghoudt test) is frequently used. Here too, pre-dominantly the horizontal permeability factor is determined. With the method used here, a monitoring well is used. The installation of the monitoring well should be done carefully.