Shallow vs Deep Foundation

Q: Which standards or codes apply?

ACI 318 (concrete), ASCE 7 (loads & combinations), ACI 351 (equipment/dynamic foundations); Thai DPT/EIT for local compliance; geotechnical report for bearing & settlement.

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Quick pick (TL;DR)

Good soil (≥ ~150 kPa) & light/moderate load → isolated footing.
Closely-spaced columns or large moments → combined/strip.
Whole-area heavy/uniform → raft.
Weak/soft soil, high water table, heavy or vibrating equipment, or strict settlement → piles (bored for low noise/urban; driven for capacity; micropile for tight access).

Step 1 — Gather the input data

Loads: vertical, moment, shear.
Soil: bearing, type, settlement, water table.
Equipment: static / vibrating; settlement limit.

Step 2 — Type selection

Type	Use when
Isolated footing	Good soil, single column.
Combined / strip	Close columns / moments.
Raft / mat	Heavy uniform / weak soil.
Piles	Weak soil / heavy / settlement.

Step 3 — Bearing & stability check

Isolated footing + moment

Given P = 400 kN , M = 80 kN·m Footing B = L = 2.5 m , q_allow = 150 kPa Step 1 — A & Z A = 2.5 × 2.5 = 6.25 m² Z = B³/6 = 2.5³/6 = 2.60 m³ Step 2 — Eccentricity e = M/P = 80/400 = 0.20 m B/6 = 0.417 m → e < B/6 → no uplift Step 3 — Bearing pressure q = P/A ± M/Z = 64 ± 30.7 q_max = 94.7 kPa < 150 → OK q_min = 33.3 kPa > 0 → full contact Step 4 — Stability FoS overturning & sliding ≥ 1.5 (check separately)

Passes with margin. If q_max > q_allow or uplift → enlarge or use piles.

Special case — vibrating equipment

Vibrating machines → heavy block ≥ 3× machine mass, tuned off resonance (ACI 351).

Footing bearing calculator

Square footing — bearing & uplift

q = P/A ± M/Z and the e < B/6 no-uplift check.

Load P (kN)

Moment M (kN·m)

Footing B (m)

Allowable (kPa)

Square footing screening — full design adds biaxial, sliding, settlement, rebar.

Common mistakes

Ignoring moment → underestimate q_max.
Ignoring settlement.
Shallow footing on fill/soft clay.

Requisition & datasheet

Loads/soil; type, size, depth, grades.
Anchor bolts; checks; code.

Frequently asked questions

What should I know about Shallow vs Deep Foundation?

Good soil (≥ ~150 kPa) & light/moderate load → isolated footing. Closely-spaced columns or large moments → combined/strip. Whole-area heavy/uniform → raft. Weak/soft soil, high water table, heavy or vibrating equipment, or strict settlement → piles (bored for low noise/urban; driven for capacity; micropile for tight access).

Which standards or codes apply?