Permeability Apparatus

Description of Permeability Apparatus:

Permeability Apparatus consists of a framed glass tank, of internal dimensions 1900 mm long by 530 mm high and 130 mm front to back. The tank is mounted on a fabricated steel frame fitted with castors and levelling feet. The front, back and ends of the tank are of clear toughened glass giving scratch free visibility without the risk of abrasion of the inner surfaces by the permeable medium. The base of the tank incorporates fourteen pressure tappings at 100 mm pitch, the tappings are specially designed to prevent the ingress of sand particles. Flexible tubes connect the tappings to two multitube manometer banks scaled 0 to 500 mm, for measure-ment of the water table height along the tank. A dye injection system allows four dye lines to be generated which highlights visualisation of flow lines and allows flow nets to be drawn for seepage analysis. Scales on the front panel assist in the preparation of models. An activated carbon decolourising filter is provided in the sump tank to prevent the progressive dis-colouration of the water by prolonged use of dye. Scales on the front panel assist in the preparation of models and in the prepara-tion and recording of flow nets. Washed silica sand graded 0.2 mm to 1.0 mm should be used as the permeable medium which must either be ordered separately from supplied by the end user. Coarser material may also be used.

Experimental Capability of Permeability Apparatus:   

1. Confirmation of Darcy’s Law and measurement of the Coefficient of Permeability  
2. Drawdown in two-dimensional horizontal flow  
3. Two-dimensional drainage test  
4. Flow through a permeable earth dam, with and without toe-filter  
5. Seepage flow under an impermeable embankment or dam  
6. Seepage flow under sheet piling and foundation slabs  Stability of slopes  
7. Demonstration of ‘piping’ in the development of ‘quicksand’ conditions  
8. Construction of flownet diagrams
9. Distribution of uplift and lateral pressures on walls and structures

Features of Permeability Apparatus:     

1. Two-dimensional permeability tank  
2. Stainless steel mesh end baffles  
3. Independently adjustable supply and drain header
4. Models of impermeable sheet piling and foundation slab
5. Permeable dam toe-filter
6. Fourteen pressure tappings and multitube manometer
7. Dye injection system for tracing flow patterns and activated carbon de-colourising filter  
8. Scratch resistant toughened glass front and rear sides