| Summary: | 碩士 === 國立中央大學 === 應用地質研究所 === 84 === Drawdown data from pumping tests exhibit certain anomalies
such as rising groundwater levels, irregular fluctuations, and
groundwater recoveries exceeding the original levels.
Theoretical studies prove that any of the anomalies indeed can
be attributed to neighboring well interference. Neglecting the
neighboring well interference effects leads to incorrect
evaluation of transmissivity(T) and the storage coefficient(S).
If the number of neighboring wells(N), the pumping rates of the
neighboring wells(Qnj, j=1,2,..,N), and the locations of the
neighboring wells(Rnj) are unknown, one neighboring well
interference can be caused by different type of neighboring well
pumping conditions, and the determination of unique combination
of N, Qnj, and Rnj becomes impossible. The purpose of this
research is to develop a method that can estimate the
groundwater parameters from drawdown data containing
interference phenomena. As a first attempt to deal with the
problem of interest, the aquifer is assumed to be confined such
that only T and S are to be determined. To avoid the possible
nonuniqueness of the solutions, the starting times of the
pumping test and the neighboring wells are assumed to be the
same, while N, Qnj, and Rnj can be unknown. A linearized least
square error fitting method is developed, and it has been
applied to the following three cases : (1) N and Rnj are known,
and Qnj, T, and S are unknown, (2) N is known and Qnj, Rnj, T
and S are unknown, (3) N, Qnj, Rnj, T and S are unknown. This
method successfully handled the three cases, using one , two ,
or three neighboring wells. In field application where only the
straight-line portion of a semilogarithmic plot of drawdown
history is used, the results do not clearly show the neighboring
well effects. This is possibly due to the fact that the straight
line portion is not sensitive to the neighboring well influence
and/or due to the assumption that the neighboring wells and the
pumping well must be started at the same time. It thus is
suggested that further study treat the pumping rate and the
distance of the neighboring well as time-dependent. This kind of
approach avoids assuming Qnj to be constant and its starting
time to be the same as the pumping well.
|
|---|
