Permeability :

The permeability of soils has a decisive effect on the stability of foundations so the determination of hydraulic conductivity of soils is substantial test and there are methods that are in common use for determining the coefficient of permeability k can be classified under laboratory and field methods :

• Laboratory methods
1. Constant head permeability method
2. Falling head permeability method

Packer Test (Lugeon Test) :

Packers are primarily used in bore holes for testing the permeability of rocks under applied pressures. The apparatus used for the pressure test is comprised of a water pump, a manually adjusted automatic pressure relief valve, pressure gage, a water meter and a packer assembly. The packer assembly consists of a system of piping to which two expandable cylindrical rubber sleeves, called packers, are attached. The packers which provide a means of sealing a limited section of bore hole for testing, should have a length five times the diameter of the hole. They may be of the pneumatically or mechanically expandable type. The former are preferred since they adapt to an oversized hole whereas the latter may not. However, when pneumatic packers are used, the test apparatus must also include an air or water supply connected, through a pressure gage, to the packers by means of a higher pressure hose. The piping of a packer assembly is designed to permit testing of either the portion of the hole between the packers or the portion below the lower packer. The packers are usually set 50, 150 or 300 cm apart. The wider spacings are used for rock which is more uniform. The short spacing is used to test individual joints which may be the cause of high water loss in otherwise tight strata. Two types of packer methods are used for testing of permeability. They are :

1. Single packer method.
2. Double packer method.

But in Al-Ahmad usually the first method is used.