Multiple coil field math for magnetic train

[pixelpuffin]

i need to know how to calculate the inductance and field strength of a coil while another coil directly beneath it is turning off and coils under that are also turning off
i also need to know how quickly the coils will turn off and if i can accelerate the process
if it makes a difference the coils are very flat (5 cm long and 1000 cm across)
links are quite appreciated too

i almost forgot the permeability of the material within the magnet will be changing and the magnets will be past 7 teslas which likely complicates things

 

[pixelpuffin]

what i need the most here is the inductance change so if anybody knows that i would like an equation or a link to an equation