Computation Analysis Of Hydrogeological Parameters Of Phreatic Aquifer Based On Pumping Test

The permeability coefficient and radius of dewatering influence of phreatic aquifer, the degree of accuracy of which have a direct impact on reliability of excavation dewatering design, are two important hydrogeological parameters in excavation dewatering design. The determination method of permeability coefficient and radius of dewatering influence is field pumping test. At present, steady flow pumping test is often used to test the permeability coefficient and radius of dewatering influence of phreatic aquifer in practice. But the test method needs much exploration and test wrok, which is often diffcult to realize.With the development and application of unsteady theory of the motion of ground water, more and more unsteady flow formula is used to find the solution of phreatic aquifer parameters. In the two cases of pumping in interferentical single well of phreatic without and with observation holes, the paper study the solution method of permeability coefficient and radius of dewatering influence according to the theory of stable and unstable flow, pointing out the shortcomings of common methods and giving methods how to solve parameters. At last , the aforementioned methods are verified by filed pumping test data in Xi'an north station, and compared to the result of steady flow pumping test formula of two observation wells, proofing the rationality and practicability of methods of this paper.Through study of the paper, some conclusions can be made as follows: 1. In the case of pumping in interferentical single well of phreatic without observation holes:â‘ Using conventional method(iterative method of Dupuit, J. -J. formula and emprical formula ) to solve permeability coefficient and radius of dewatering influence is short of the theory evidence;â‘¡When having more drawdown of pumping well(0.1H