Permeability Testing
Permeability Testing
(OP)
Hi All,
I have a few queries regarding permeability testing and applicability.
Geology for my site consists of ~6m of clayey silt, overlying a saturated sand and gravel deposit. The sand and gravel deposit is the source of the towns groundwater so I assume that the recharge rate must be fairly high. I have a couple of wells installed, (50mm diameter, with slotted lower casings). One well is installed with the slotted pipe in the gravel layer, sand around the screen, and then is sealed from the top of the screen to the surface with bentonite. The other well is installed in the clayey silt, similar installation details.
It seems to me that there are two ways I could test the permeability: I could add water to the pipe, and then measure how long it takes for the head to drop; or, I could pump/bail the water out and measure how fast it takes to recharge.
Would both methods give the same permeability?
I have a few queries regarding permeability testing and applicability.
Geology for my site consists of ~6m of clayey silt, overlying a saturated sand and gravel deposit. The sand and gravel deposit is the source of the towns groundwater so I assume that the recharge rate must be fairly high. I have a couple of wells installed, (50mm diameter, with slotted lower casings). One well is installed with the slotted pipe in the gravel layer, sand around the screen, and then is sealed from the top of the screen to the surface with bentonite. The other well is installed in the clayey silt, similar installation details.
It seems to me that there are two ways I could test the permeability: I could add water to the pipe, and then measure how long it takes for the head to drop; or, I could pump/bail the water out and measure how fast it takes to recharge.
Would both methods give the same permeability?





RE: Permeability Testing
This is similar to discussions we have in our company. We perform DRI testing and some engineers will report an unsaturated vertical hydraulic conductivity. The DRI estimates infiltration not permeability in my opinion. The boundary conditions are unknown in a DRI.
I'm interested to hear feedback from some of the more experienced engineers on here.
RE: Permeability Testing
Given your description, a slug test is likely the best option in the clay and an pumping test in the sand/gravel.
Mike Lambert
RE: Permeability Testing
I would also encourage you to do grain-size distribution and correlate to permeability as a reference point to your test.
I would also encourage you to look at the various test conditions of Hvorslev.
f-d
ípapß gordo ainÆt no madre flaca!
RE: Permeability Testing
RE: Permeability Testing
My thinking was that since the purpose of the test is to provide the town with a site-specific permeability they can use to determine stormwater infilitration, the 'adding water' test would be more applicable since it seems directly analogous to what they are trying to do, even if the permeability is lower
RE: Permeability Testing
This is one reason that the Johnson or Guelph permeameters are used in infiltration design.
f-d
ípapß gordo ainÆt no madre flaca!