Soil Permeability Tests

These tests are used to determine the permeability of the soil stratum at various levels below the ground water table . The site supervisor should record the results and phenomenon during the test and hand in to the Geological Engineer for assessment . The preparation work and principle of the various tests are as follows : -

Preparation work :
1. to survey the coordinates of the driven bored hole ,
2. to note down the size of casing ,
3. to survey the existing ground level ,
4. to calculate the level of the top of casing by measurement above existing ground level ,
5. to calculate the level of the bottom of casing by deduction of casing lengths , and
6. to calculate the level of ground water table with a dip meter .

Rising Head Test :
Pump away the water inside the casing of bored hole to a level above bottom of casing and below ground water table . When the test starts , check the pumped-down water level with a dip meter and record the time . Let the water level rises until it is stable at ground water table and accordingly check the various water levels at a fixed time interval .

Constant Head Test :
To fill water to the top of casing such that a certain water column is added on above the ground water table and record the time of test . Let the water seeps away but continuously add up with water to maintain the level at the top of casing . Record the volume of water subsequently added and the duration of testing .

Falling Head Test :
To fill water to the top of casing such that a certain water column is added on above the ground water table and record the time of test . Let the water seeps away until it is stable at ground water table and accordingly check the various water levels at a fixed time interval .