How is pile settlement calculated?

Two standard ways: Vesić's (1977) three-component method (elastic shortening of the shaft + settlement from tip load + settlement from shaft-transmitted load), and the t-z load-transfer method, which mobilizes side and base resistance against movement to build the full load–settlement curve. This calculator does both.

How much settlement is acceptable for a pile?

Many structures tolerate 10–25 mm (0.5–1 in) of total settlement at working load; the governing criterion is usually differential settlement between supports. Side resistance mobilizes within a few millimetres, while end bearing may need 5–10% of the tip diameter — so working-load settlement is normally small.

Why does settlement rise sharply near ultimate load?

Once side friction is fully mobilized, additional load transfers to the tip, which requires much larger movement per increment of resistance. The load–settlement curve therefore steepens dramatically as the load approaches ultimate capacity — visible directly on the curve this tool plots.

Free Pile Settlement Calculator (Vesić + t-z method)

How to use it

Describe the pile and soil

Same inputs as the capacity calculator — pile type, geometry, soil strength, water table.

Enter the working load

The design (service) axial load at the pile head.

Read the settlement

The tool computes capacity, builds the t-z / q-w load–settlement curve, and reports the head settlement at your load plus Vesić's breakdown (elastic shortening, point, and shaft-transmitted settlement).

How pile settlement is computed

Two established methods, run together. Vesić (1977) splits settlement at a given load into three parts: elastic shortening of the shaft (the pile compressing as a column), settlement caused by the load reaching the tip, and settlement caused by the load shed along the shaft. The t-z / q-w load-transfer method goes further: it mobilizes side and base resistance against movement using the Reese & O'Neill (1988) normalized transfer curves, producing the full load–settlement curve — from which this tool reads the settlement at your working load rather than at ultimate.

Why the curve matters more than one number

Side friction mobilizes within a few millimetres of movement; end bearing needs movement of roughly 5–10% of the tip diameter. So the load–settlement curve is steep and nearly linear at working loads — where the shaft does the work — and flattens dramatically as load shifts to the tip near ultimate. That shape is why a pile at FS = 2.5 typically settles millimetres, not centimetres, and why settlement rather than capacity often governs large drilled shafts. The mechanics are unpacked in skin friction vs end bearing and the axial documentation.