The theoreitical improvement and development of circulation flow test.

• Main Authors: Kung-Lin Lee, 李岡林
• Other Authors: Chia-Shyun Chen
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/75093472864410315246

碩士 === 國立中央大學 === 應用地質研究所 === 92 === Single-well tests are less expensive than multiple well tests in hydrogeologic investigation. Single-well tests also withdraw limited amount of water and hence are suitable for contamination sites. The dipole flow test (DFT) is a single-well circulation flow test (CFT), which generates a circulation flow field in the aquifer by pumping water in the upper well screen section using a constant flow rate +Q and discharging the pumped water through the lower well screen section in -Q. In theory, DFT is able to estimate the horizontal hydraulic conductivity (Kr), the vertical hydraulic conductivity (Kz), and the storage coefficient (S).However, field experiments of DFT under different hydorgeological conditions showed that DFTs reached steady state rapidly, unfavorable for the estimation of Kz and S. This study improves the design of DFT, and develops the constant head circulation flow test (CHCFT), which generates a circulation flow field in the aquifer by pumping water in the upper well screen section using a positive constant head and discharging water through the lower well screen section using a constant negative head (drawdown). This constant-head condition renders CHCFT to reach steady state after a long period time, during which Kr, Kz, and S can be determined without difficulty. However, current constant drawdown pumping techniques can not discharge water continuously with a constant water level between 8 to 45 meters below ground surface, and makes the application of CHCFT limited. Hence we replace the constant drawdown pumping in CHCFT with a constant rate pumping which has less limitation on the drawdown level and develop another CFT model: constant rate – constant head circulation flow test (QHCFT). Due to two different pumping techniques are applied in two different screen sections, QHSCT reaches steady state after a long period as CHCFT, and Kr, Kz, and S can be determined without difficulty. When developing CHCFT and QHSCT, both confined and unconfined condition with skin effect are considered, and the type curve analysis is tested with hypothetical data for the determination of skin factor (Sk), Kr, Kz, and S. It is found if skin exists but its effect is neglected will result in a false determination of Kz and S.