1D Consolidation

When a wide load goes on a saturated clay, the water takes it all. As the water drains away it hands the load over to the grains, and the ground settles as it does. See how fast that handover happens, and what drainage, drains and overconsolidation do to it.

What you are seeing

• Settlement with time. The settlement curve shows the handover in time (solid blue). The dashed grey line is the final settlement; the black dot and dotted line mark the profile time. With drains on, the dotted grey curve is the same layer without them.
• Load share. The handover through the layer at the profile time: at each depth the brown width is the grains' share of the added load, Δσ′, and the blue width is the water's, the excess pore pressure u. The grains take over first next to the drains.

The model

Drainage: Drained boundaries force u = 0. Impermeable boundaries trap water and slow dissipation.

Drains shorten the drainage path to about half their spacing, so the time falls with its square. The radial flow to a drain is approximated here by one-dimensional flow over that distance, combined with vertical drainage by Carrillo's rule, 1 − U = (1 − U_v)(1 − U_r): a scaling estimate, not a design calculation.

Reloading below the preconsolidation stress uses C_r instead of C_c: m_v is six times smaller and, with the same permeability, c_v is six times larger. The settlement is smaller and faster.