Chapter 19: Single Vertical Dikes. Analysis and Evaluation of Pumping Test Data Second Edition. Background. Two types: Igneous Sedimentary Igneous dikes are formed when magma rises through the subsurface and intrudes, or cuts through, pre-existing strata.
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Chapter 19: Single Vertical Dikes
Analysis and Evaluation of Pumping Test Data
Dikes can be highly permeable.
If a single, permeable, vertical dike bisects an aquifer whose transmissivity is several times less than that of the dike, a specific flow pattern will be created when the dike is pumped.
“Trough of Depression” similar to
cone of depression
To analyze the drawdown behavior for early and medium times along the pumped dike:
WdTd = 2.6 x 104m3/d
WdSd = 4.3 x 10-4m
S T = 3.2 x 10-4 m2/d
To analyze early and medium time drawdown behavior in observation wells drilled in the aquifer along a line perpendicular to the dike and even with the pumped well:
T/S = 2.7 x 105 m2/d
Combining results from observation wells in the dike and aquifer, we get separate values for transmissivity and storativity of the aquifer:
T = 9.3 m2/d
S = 3.4 x 10-5
At early times, all the pumped water is from dike storage (no water from aquifer storage).
At medium times, most of the drawdown is governed by parallel flow from the aquifer into the dike (no water from dike storage).
At late times, the flow in the aquifer is no longer considered parallel, but rather pseudo-radial.
Solution for the drawdown in the pumped well during late time:
For a pumping test of usual duration, this method can only be applied to fractures or thin dike structures.
(WdTd) √(ST) = 425 m4/d3/2
Substituting the values of dike width and transmissivity(WdTd) and aquifer storativity and transmissivity (ST) obtained with Boonstra – Boehmer’s method into (WdTd) √(ST), the value is 465.