Free Web Tool

Mat (Raft) Foundation

Compute soil contact pressures and approximate settlement for a rigid mat/raft foundation under biaxial eccentricity.

Inputs

Mat Length L (m)

Mat Width B (m)

Total Service Load ΣP (kN)

Allowable q_net (kPa)

Eccentricity ex (m)

Eccentricity ey (m)

Subgrade ks (kN/m³)

Mat Thickness t (m)

Method

q = ΣP/A ± 6·ΣP·ex/(B·L²) ± 6·ΣP·ey/(L·B²) (rigid mat, biaxial eccentricity).
Check q_max ≤ qa and q_min ≥ 0 (otherwise tension/uplift develops).
Approximate settlement δ ≈ q/ks. Differential settlement δd ≈ 0.5·δ.

Results

Mat Area—

Avg Pressure q_avg—

q_max—

q_min—

Settlement δ—

Status—