Underpinning Method of Foundation

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Underpinning stands as a vital technique for repairing and fortifying building foundations. It involves strategic reinforcement of an existing base to distribute weight over a larger area, ensuring stability. Two common methods, micro-piling, and jet grouting, though time-consuming and expensive, play crucial roles in this process.

The Need for Foundation Underpinning:

When a building undergoes structural changes due to settlement or damage, immediate observation and measurement become imperative. The urgency depends on the severity of the settlement, prompting experts to examine the soil’s capability to support the structure. Underpinning becomes necessary when the foundation faces weakening, allowing for the installation of stronger materials and deeper footings.

Classifying Buildings and Underpinning Methods:

Building Age Classification:

Understanding a building’s age is essential for selecting underpinning methods:

  • Ancient Structures (over 150 years old)
  • Recent Structures (50 to 150 years old)
  • Modern Structures (under 50 years old)

Types of Works:

– Conversion Works : Transforming a building for a different purpose necessitates a stronger foundation.

– Protection Works : Addressing issues like unreliable foundations, soil compromise, and protection against disasters.

– Remedial Works : Improving existing structures due to initial foundation design errors.

Structural Conditions Requiring Underpinning:

Engineers recommend underpinning for various reasons, including:

  • Traditional buildings on deteriorating wood piles.
  • Unstable soil structures leading to building damage.
  • Settlement issues for structures on unstable ground.

Exploring Underpinning Methods:

Pit Method or Mass Concrete Underpinning : Utilizing stages to reveal soil layers and backfilling with concrete for stability.

Pile Method of Underpinning : Installing piles through driving techniques for wall reinforcement.

Jack Pile Method of Underpinning : A silent and adaptable option for areas with depth challenges.

Root Pile or Angle Piling : Utilizing concrete drilling technologies for stability.

Pynford Stool Method : Continuous underpinning without needles or shoring for weakened foundations.

Underpinning Columns : Supporting columns similar to walls with conventional or jack piles.

Advantages of Underpinning:

  • Strengthening foundations against disasters.
  • Adding natural light and space to buildings.
  • Accessing and inspecting home infrastructure.
  • Enhancing property value and future selling potential.
  • Cost-effective space addition compared to buying a new house.

Disadvantages of Underpinning:

  • Expansive nature of underlying foundation methods.
  • Challenges in underpinning on unstable and flooded ground.
  • Disposal of a significant volume of excavated material.

Conclusion:

Underpinning emerges as a crucial technique for reinforcing and restoring building foundations, addressing structural weaknesses, and increasing load capacity. Its diverse methods cater to different building ages and structural requirements, making it an indispensable solution for maintaining and enhancing the integrity of existing structures.