Foundation Settlement – Types, Causes & Correction Methods

The foundation is the lowest part of a building, carrying its weight and ensuring stability. A well-designed foundation spreads the load over the ground, avoiding excessive pressure. However, when the foundation settles too much, it can jeopardize the structure’s safety.

Causes of Foundation Settlement

Let’s explore common reasons for foundation settlement:
Expansive Soil:

• Example: Black soil in central India swells with water absorption, causing settlement.
• Solution: Ensure proper drainage before building on expansive soils.

Non-compacted Soil:

• Risk: Loose soil threatens structure safety.
• Solution: Compact soil adequately, avoiding over-excavation.

Change in Moisture Content:

• Issue: Excessive moisture changes lead to soil settlement.
• Solution: Address drainage issues and prevent water table increases.

Consolidation – Immediate, Primary & Secondary:

• Process: Soil settles under the structure’s load over time.
• Impact: Settlement can take hours to decades, depending on soil type.

Low Safe Bearing Capacity:

• Concern: Some soils can’t bear the structure’s load.
• Solution: Conduct soil tests and plate load tests for accurate foundation design.

Trees & Vegetation:

• Threat: Roots disturb soil and absorb moisture.
• Impact: Shallow foundations are more vulnerable than deep ones.

Types of Foundation Settlement

Now, let’s delve into the types of foundation settlements:
Uniform Settlement:

• Description: Overall sinking of the structure.
• Effect: Minimal impact on structural integrity but disrupts utilities.

Differential Settlement:

• Result: Unequal vertical movement of foundations.
• Consequence: Leads to cracks, structural tilt, and door/window issues.

Tipping Settlement:

• Occurrence: Structure tilts to one side over time.
• Risk: May cause overturning with prolonged settlement.

Correcting Foundation Settlement

Discover methods to correct and prevent foundation settlement:
Site Inspection & Correction:

• Check: Drainage, waterlogging, nearby trees, and underground leaks.
• Action: Address external factors causing settlement.

Underpinning:

• Method: Strengthen foundations by transferring load to deeper strata.
• Use: Often combined with shoring for added stability.

Grouting:

• Process: Injecting liquid into soil to prevent erosion and improve load capacity.
• Types: Chemical grouting and jet grouting.

Acceptable Limits for Settlement

Know the maximum allowable settlement for different foundation types: