DETERMINATION OF PARAMETERS FOR UNEQUAL-RATE UNSTEADY FLOW DOUBLE-EXTRACTION WELL PUMPING TEST

Conventional fitting curve method and linear graphic method which could be used in aquifer parameters inversion for single well unsteady pumping test are transformed based on superposition principle,and then are applied in double extraction well unequal-rate,simultaneous unsteady flow pumping test with only one observation well.Taking Pudong working shaft of Shanghai South Xizang road river-crossing tunnel for example,according to the actual layout of well point,a particular type curve is plotted,then the transformed curve method,linear graphic method and numerical method are respectively used to determine the hydrological parameters.Moreover,the accuracy and main error sources of these three methods are compared.The results show that the hydrological parameters obtained by transformed linear graphic method are more accurate;if observation well is arranged adjacent to extraction wells,the measured drawdown curve at the initial stage of pumping test may be steeper,and eventually reduces the accuracy of inversed hydrological parameters.