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Safe Bearing Capacity of Soils

IS 1904:1986 · Table 1 — Presumptive Bearing Capacity Values

Safe bearing capacity (SBC) for preliminary foundation design. These are presumptive values per IS 1904 — for detailed design, conduct soil investigation (SPT, plate load test). SBC depends on depth of foundation, water table, and soil condition.

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18 items shown

Soil Types

Presumptive values per IS 1904 — for preliminary design only

Soil Type	SBC Min	SBC Max	Unit	SPT N	Note
Rock — hard (granite, basalt, gneiss)	3240	3240	kN/m²	>100	Intact, no weathering
Rock — soft (sandstone, limestone)	1620	1620	kN/m²	>60	Slightly weathered
Rock — soft/fractured	880	880	kN/m²	40–60	Weathered, fractured
Gravel — dense (GW, GP)	440	440	kN/m²	>30	Well-graded or poorly-graded
Sand — dense (coarse)	440	440	kN/m²	>30	N > 30
Sand — medium dense (coarse)	245	245	kN/m²	10–30	N = 10–30
Sand — loose (coarse)	100	100	kN/m²	<10	N < 10
Sand — dense (fine)	300	300	kN/m²	>30	N > 30
Sand — medium (fine)	150	200	kN/m²	10–30	N = 10–30
Sand — loose (fine)	75	100	kN/m²	<10	N < 10
Clay — hard (stiff)	440	440	kN/m²	>25	N > 25, qu > 200 kPa
Clay — medium stiff	200	245	kN/m²	8–25	N = 8–25
Clay — soft	100	150	kN/m²	2–8	N = 2–8
Clay — very soft	50	75	kN/m²	<2	N < 2
Black Cotton Soil (expansive)	50	100	kN/m²	2–8	Swelling clay — use under-reamed piles
Murum (laterite gravel)	200	300	kN/m²	15–30	Common in Deccan region
Filled-up / made-up ground	50	100	kN/m²	<10	Recently filled — avoid or compact
Compacted fill (controlled)	150	200	kN/m²	10–20	Engineered fill, 95% MDD

Practical Notes

• Presumptive SBC is for preliminary design ONLY — always do soil investigation for final design

• Depth of foundation: minimum 1.0m below ground level (IS 1904)

• Water table: reduce SBC by 50% if water table is at foundation level (sand/gravel)

• For clay soils, settlement governs more than bearing capacity

• Black cotton soil: use under-reamed piles or raft foundation, minimum 1.5m depth below active zone

• SPT N-value correlation is approximate — varies with soil type and correction factors

• Factor of safety: IS 1904 presumptive values already include FOS of 2.5–3.0

• For important structures: conduct SPT at every 1.5m depth, minimum 2 boreholes

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Live Loads (Imposed Loads)

Material Quantities per Unit of Work

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