What is the main purpose of this code?

To provide a framework for designing and constructing foundations on soils that swell and shrink with moisture changes, ensuring the stability of the structure.

How is the expansiveness of soil classified?

Using the 'Differential Free Swell' index, soils are classified as having Low, Medium, High, or Very High potential for expansion (Table 1).

What is a common foundation type recommended for highly expansive soils?

Under-reamed pile foundations are frequently recommended as they can be anchored in stable soil strata below the zone of moisture fluctuation (Clause 6.2).

What key precaution is mentioned for all foundation types in expansive soils?

To ensure that the foundation is placed at a depth where volumetric changes in the soil are negligible, or to provide a structural system that can accommodate or resist these changes (Clause 5).

IS 8009 Part 1

: 1976

Code of practice for foundation on expansive soils - Plain and reinforced concrete foundations

CurrentEssentialCode of PracticeBIMGeotechnical · Soil and Foundation

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This code provides guidelines for the design and construction of plain and reinforced concrete foundations on expansive soils, like black cotton soil. It covers site investigation, design principles, and precautions to mitigate the effects of soil swelling and shrinking. The code details various foundation types suitable for these conditions, including strip, raft, and under-reamed pile foundations.

Provides guidelines for the design and construction of plain and reinforced concrete foundations in expansive soils.

Quick Reference Values

Degree of expansion for 'High' classification35-50% Differential Free Swell

Typical depth to neglect seasonal moisture variation1.5 m to 3.5 m

Minimum grade of concrete for RCC foundation (by reference to IS 456:1978)M15

Minimum clear cover for foundation reinforcement (by reference to IS 456:1978)40 mm

Practical Notes

The primary strategy is to either bypass the zone of moisture fluctuation with deep foundations (like under-reamed piles) or create a rigid foundation system (like a raft) that can withstand differential movement.

Under-reamed piles, detailed in IS 2911, are a very common and effective solution for these soils, anchoring the structure in a stable stratum.

Effective surface drainage around the building is non-negotiable to prevent water ingress into the foundation soil, which is the primary trigger for swelling.