Question

my professor asked us to answer a question i do not understand. Where does the analogy (spring-piston) break down?

Answer 1

Answer:-

The analogy (spring-piston) break down.

1. Load on the piston with valve opened (c): water will be forced out through the valve at a rate controlled by the bore diameter (i.e. permeability of the soil). This will enable the cylinder to move and the spring to be packed as burden is bit by bit exchanged to it (for example compressibility of soil skeleton).
2. At any time, the increase in load on the spring will correspond to the reduction in water pressure. The heap conveyed by the spring speaks to the compelling worry in the dirt,
3. The development of the cylinder speaks to the adjustment in volume on the dirt and is administered by the compressibility if the spring. 
4. Finally, the load will be carried by the spring, this corresponds to the drained condition in the soil.