Calculation method and system for unstable seepage field of strip-shaped foundation pit

The invention discloses a calculation method and system for an unsteady-state seepage field of a strip-shaped foundation pit, and the method comprises the steps: dividing a target strip-shaped foundation pit into an inner region and an outer region of the foundation pit, and respectively building seepage control equations of the two regions based on the Darcy law and a two-dimensional seepage conceptual model; performing Laplacian, Fourier transform and inverse Fourier transform on definite solution conditions of seepage problems of the two regions by combining initial conditions and boundary conditions of the two regions to obtain a depth reduction expression of each region containing unknown quantity in a Laplace space; discretizing the unknown quantity on the common surface of the two regions, constructing a depth reduction matrix equation set and solving the unknown quantity in the discrete form, and substituting the unknown quantity in the discrete form into the depth reduction expression of each region