These tests are used to determine the permeability of the soil stratum at various levels below the groundwater table. The site supervisor should record the results and phenomenon during the test and hand into 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 groundwater 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 groundwater 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 groundwater 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 groundwater 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 groundwater table and record the time of test. Let the water seeps away until it is stable at the groundwater table and accordingly check the various water levels at a fixed time interval.