Permeability tests field pumping

Pumping tests are done in many ways and under many different conditions of soil stratification and water table location. Details of field pumping tests to determine permeability are given in Chapter 15. 

When reliable data on grain size or permeability are not available, it is more direct and often less expensive to run field pumping tests rather than take borings. 

Figure 15.1 shows the parameters pertinent to a field pumping test for permeability determination. One test well is required, and two observation wells are needed, both within the drawdown curve and at different radial distances from the test well. The test well is pumped at some constant rate until equilibrium elevations are attained in the observation wells. Field measurements of Q, ri, r2, hi, and h2 are taken. Permeability is computed from... 

On the other hand, simply pumping fluid into a formation bypasses boring, sampling, and permeability testing and establishes directly whether or not a formation will accept grout. (Field tests can also establish permeability values, if such data are needed, with greater accuracy than laboratory tests.)... 

A pumping test was conducted in the field on an 11-foot-thick horizontal stratum of medium sand with a trace of silt. The water table was at the surface of the sand, which was underlain by clay. Equilibrium was established when pumping 20 gallons per hour. Water elevations in observation wells 10 feet and 20 feet from the pumping well were 4.7 and 2.9 feet below the surface. What is the permeability of the sand ... 

PUMPING TEST A field procedure used to determine in situ permeability or the ability of a formation to aecept grout. 

Determination of the permeability in the field can be done by measuring the time it takes for a tracer to move between two test holes. As with pumping tests, this tracer technique is based on the assumption that the aquifer is homogeneous and that observations taken radially at the same distance from the well are comparable. This method of assessing permeability requires that injection and observation wells be close together (to avoid excessive travel time) and that the direction of flow be known so that observation holes are correctly sited. 

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