ABSTRACT
Methods of non-stationary filtration are used in many technologies: rapid dewatering of excavation, drainage of construction sites, etc. Determination of the instantaneous groundwater level is associated with the solution of non-stationary filtration problems. Classical calculation methods of the depression curve are related to the solution of the limit problems for the Laplace equation (in domains with free boundary). This paper considers a different idea. The steady-state filtration mode is obtained as the limit of instantaneous filtering modes. Instantaneous modes are formed by the rapid lowering of the water level in the basin or in the drained well. The results of the mathematical analysis are adjusted to the calculation formulas that can be used to determine the dewatering time of excavation, drainage performance, etc.
