Evaluation of hydraulic parameters from pumping tests in multi-aquifers with vertical leakage in Tianjin

Abstract

This paper presents a case history of behaviour during a series of pumping tests in an alternated multi-aquifer-aquitard system in a foundation pit in Tianjin, China. The test site is located at Tianjin Railway Station, which is in the downtown area and is surrounded by many buildings. The groundwater system at the test site is composed of a phreatic aquifer and three confined aquifers. Four groups of single well pumping tests were conducted in each aquifer to obtain the hydrogeological parameters of the aquifers and investigate the hydraulic connection among the aquifers. Test results show that there is hydraulic connection among the upper 3 aquifers. Moreover, both analytical and numerical methods were employed to analyse the hydrogeological parameters. The analytical solution was obtained for the phreatic aquifer using the Dupuit equation, and the Cooper–Jacob method was conducted for the confined aquifers. The numerical simulation was performed using a finite element method (FEM). The results illustrate that the numerical method gives more reliable results than the analytical method does. The numerical simulation considers the anisotropic characteristic of soils, and the hydrogeological parameters of all of the soils can be calculated. The analytical solution, however, may be influenced by wellbore storage or by the leakage effect of the aquitards, and it only gives the parameters of the aquifer where the pumping tests were performed.