Ground engineering · Consolidation & preloading

Preloading with surcharge calculator

Surcharge needed so that primary settlement under the permanent load is removed by a target time, with the degree of consolidation achieved.

Standard: Terzaghi 1D consolidation · Tv–U relation

Inputs in the worked example

The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.

Result	Value	Unit
Drainage path	4.00	m
Tv = cv t/Hdr²	0.250
U(Tv)	0.564
Final settlement under permanent load mv Δσ H	192.0	mm
Total pressure needed (qp/U)	106.3	kPa
Extra surcharge	46.35	kPa

Diagram for the worked example

Drainage path = 8/2 = 4 m
Tv = cv t/Hdr² = 2*24/12/4^2 = 0.25
U(Tv) = IF(0.25<=0.2827,SQRT(4*0.25/PI()),1-8/PI()^2*EXP(-PI()^2*0.25/4)) = 0.56419
Final settlement under permanent load mv Δσ H = 0.4/1000*60*8*1000 = 192 mm
Total pressure needed (qp/U) = 60/0.56419 = 106.35 kPa
Extra surcharge = 106.35-60 = 46.347 kPa

Consolidation settlement — Primary settlement (NC or OC clay) and time to a degree of consolidation.
Prefabricated vertical drains — Radial consolidation with smear, time to target degree, triangular or square spacing.
1D consolidation: multi-layer finite difference — Layered clay with different cv and mv, drained at the top, bottom or both. Solves the consolidation equation…
Wick drains with preload: time–settlement (Hansbo) — Prefabricated vertical drains in a soft clay under a preload with surcharge. Equivalent drain diameter…
Settlement monitoring: Asaoka and hyperbolic prediction — Predicts the final settlement from settlement-plate readings at a constant interval by two independent…
Stone columns (Priebe) — Area replacement ratio and basic settlement improvement factor for a stone column grid.

For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.