帯水層定数の決定に関する研究 (III)

回復法における井戸特性の影響

抄録

A recovery test is widely used as a simple aquifer test. Though recovery of water level in a pumped well is greatly affected by well characteristics, they have been neglected in recovery tests. Therefore, in this paper the method of recovering water level is investigated with well characteristics taken into consideration.
First, it is discussed that well characteristics as mentioned in the previous paper are approximately expressed by a single parameter α'. And a recovery curve of a lowering of water level with well characteristics taken into account has been derived from the result of analysis of pumping at a constant rate. From this the following conclusions have been reached:
i) The s-log (t/t-t0) curve does not take a liner form as obtained from the well function, but takes an S-shaped form when well characteristics are taken into consideration.
ii) For a constant pumping time, the amount by which a recovery curve deviates from the straight line obtained from the well function increases with an increase in the value of C', where C'=α'/ 2S is a storage factor.
It has been found from the above-mentioned that in order to obtain a correct value of transmissibility, we should use the gradient of s-log (t/ t-to) curve at the limit of t→∞.
Finally, it has been confirmed by the recovery curve obtained in a pumping test carried out previously that the treatment mentioned above is proper.