What Is Under-Reamed Pile Foundation | Uses of Under-Reamed Piles | Advantages & Disadvantages of Under-Reamed Piles | Application of Under Reamed Piles

What Is Under-Reamed Pile Foundation?

Under reamed piles are bored cast-in-situ concrete piles having one or more number of bulbs formed by enlarging the pile stem. These piles are best suited in soils where considerable ground movements occur due to seasonal variations, filled-up grounds, or in soft soil strata.

Development History of Under-Reamed Pile

Under–Reamed Piles are bored cast-in-situ concrete piles having one or more number of bulbs formed by enlarging the piles stem. The piles are best suited in soils where considerable ground movements occur due to seasonal variation, filled-up grounds, or in soft soil level.

Definition of Under-Reamed Pile

Under reamed piles are bored cast-in-situ concrete piles having one or more number of bulbs formed by enlarging the pile stem. These piles are best suited in soils where considerable ground movements occur due to seasonal variations, filled-up grounds, or in soft soil strata.

Uses of Under-Reamed Piles

The provision of under-reamed bulbs has the advantage of increasing the bearing and uplift capacities. It also provides better anchorage at greater depths. These piles are efficiently used in machine foundations, over bridges, electrical transmission tower foundation sand water tanks.

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Advantages of Under-Reamed Piles

It decreases the vertical settlement and also differential settlement. It is used when soil tends to swell and shrink due to moisture variation or the expansive nature of the soil. Provision of under-reams or bulbs has the advantage of increasing the bearing and uplift capacities.

Disadvantages of Under-Reamed Piles

• At a depth where the nature of soil varies with a climatic condition, Under–Reamed Piles are not suitable for waterlogged soil, as they take load by friction.
• These piles need strict quality control and regular supervision during construction.

Features and Details of Under Reamed Piles

Under–Reamed Piles are bored cast-in-situ concrete piles having one or more number of bulbs formed by enlarging the piles stem. The piles are best suited in soils where considerable ground movements occur due to seasonal variation, filled-up grounds, or in soft soil level.

Increasing Load-Carrying Capacity of Under Reamed Piles

The ultimate load-bearing capacities of piles are maximum when the spacing between two reamed bulbs is 2.5 times the diameter of the under-reamed bulb. It appears that the spacing between two under-reamed bulbs suggested in (1.25 to 1.5 times) IS 2911(1980) is not the optimum, 5.

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Application of Under Reamed Piles

The provision of under-reamed bulbs has the advantage of increasing the bearing and uplift capacities. It also provides better anchorage at greater depths. These piles are efficiently used in machine foundations, over bridges, electrical transmission tower foundation sand water tanks.

Is Code for Pile Foundation

Following are the Indian Standard Codes on Pile Foundations: IS 2911 : Part 1 : Sec 1 : 1979 Driven cast-in-situ concrete piles. IS 2911 : Part 1 : Sec 2 : 1979 Bored cast-in-situ piles. IS 2911: Part 1 : Sec 3 : 1979 Driven precast concrete pile.

Under Reamed Pile Design Example

Under reamed piles are bored cast-in-situ concrete piles having one or more bulbs formed by enlarging the pile stem. These piles are best suited in soils where considerable ground movements occur due to seasonal variations, filled-up grounds, or in soft soil strata.

Under-Reamed Pile Foundation Design

Under-reamed pile foundations are a type of deep foundation system commonly used to support structures on soft and compressible soils. These foundations are designed to increase the bearing capacity of the soil by creating bulb-shaped enlargements, called under-reams, at the base of the piles. The under-reams provide additional resistance against uplift and lateral loads.

Here are the general steps involved in the design of under-reamed pile foundations:

• Site investigation: Conduct a thorough geotechnical investigation of the site to determine the soil properties, including its bearing capacity, compressibility, and groundwater conditions. This information is crucial for designing the pile foundation.
• Load analysis: Determine the loads that the foundation needs to support, including dead loads, live loads, and any additional imposed loads. Consider both vertical and horizontal loads acting on the structure.
• Pile layout: Determine the spacing and arrangement of the piles based on the loads, soil conditions, and structural requirements. The number and diameter of piles are typically determined based on the structural loadings.
• Under-ream design: Determine the dimensions and shape of the under-reams. The under-ream diameter is usually larger than the pile shaft diameter, and its depth is typically determined based on the design requirements and soil conditions.

Under-Reamed Pile Foundation Construction Process

The construction process for under-reamed pile foundations typically involves the following steps:

1. Excavation: Excavate the site to the required depth for the pile foundation. The depth is determined based on the design requirements and the soil conditions. The excavation can be done using various methods such as drilling or augering.
2. Under-ream formation: Once the excavation is complete, create the under-reams at the base of the pile. Under-reams are bulb-shaped enlargements that provide additional bearing capacity. This is typically done using under-reaming tools or specially designed drill bits. The diameter and depth of the under-reams are determined based on the design specifications.
3. Reinforcement placement: Install the reinforcement cages or bars into the under-reams and along the pile shaft. The reinforcement provides tensile strength to the pile and helps resist bending moments and shear forces. The reinforcement should be positioned as per the design requirements and should be adequately spaced and tied together.
4. Concrete pouring: Pour concrete into the excavated holes, ensuring that it fills the under-reams and encases the reinforcement. The concrete mix should be appropriate for the project specifications and should be placed using proper techniques to minimize segregation and ensure good quality.

Benefits of Under-Reamed Pile Foundations

Uses of Under-Reamed Piles

• To avoid the undesirable effect of seasonal moisture changes in expansive soils such as black cotton soils.
• To reach hard strata.
• To obtain adequate capacity for downward, upward, lateral loads and moments.
• To take the foundations below the scour level.

Under-Reamed Pile Foundation Cost Estimate

The cost estimate for under-reamed pile foundations can vary depending on several factors, including project-specific requirements, local labor and material costs, site conditions, and the size and complexity of the structure.

Under-Reamed Pile Foundation Design Guidelines

When designing under-reamed pile foundations, it is important to follow certain guidelines to ensure the stability, load-bearing capacity, and structural integrity of the foundation system. Here are some general design guidelines for under-reamed pile foundations:

• Geotechnical investigation: Conduct a comprehensive geotechnical investigation to characterize the soil properties, including strength, compressibility, and groundwater conditions. This information is crucial for determining the appropriate design parameters and under-ream dimensions.
• Load analysis: Determine the loads that the foundation needs to support, including dead loads, live loads, and any additional imposed loads. Consider both vertical and horizontal loads acting on the structure.
• Pile spacing and arrangement: Determine the spacing and arrangement of the piles based on the loads, soil conditions, and structural requirements. The number and diameter of piles are typically determined based on the structural loadings.

Under Reamed Pile Foundation

Under-reamed pile foundations are a type of deep foundation system that is commonly used to support structures on soft and compressible soils. These foundations are designed to increase the bearing capacity of the soil by creating bulb-shaped enlargements, called under-reams, at the base of the piles. The under-reams provide additional resistance against uplift and lateral loads.

Under Reamed Piles Are Generally

Under reamed piles are bored cast-in-situ concrete piles having one or more number of bulbs formed by enlarging the pile stem. These piles are best suited in soils where considerable ground movements occur due to seasonal variations, filled up grounds or in soft soil strata.

What Is Under Reamed Pile Foundation?

A cast-in-situ concrete pile with an enlarged bulb at bottom made by either cutting or scooping out soil or by any other suitable process is called Under-Reamed Pile. Under-Reamed Piles are also called bored cast-in-situ concrete piles.

What Type of Method of Installation Can Be Used for the Under Reamed Piles?

Under-Reamed Piles are bored cast-in-situ concrete piles having one or more number of bulbs formed by enlarging the piles stem. The piles are best suited in soils where considerable ground movements occur due to seasonal variation, filled up grounds or in soft soil level.

What Is Bulb in Pile Foundation?

The bottom end of the pile has a spherical enlarged portion called an under rim or bulb. The diameter of the pile is 20 cm to 50 cm and the diameter of the bulb is 2 to 3 times the diameter of the pile. Under reamed Pile lengths range from 3 m to 8 m.

What Is Pile Foundation?

Pile foundations are long, thin elements generally made of steel or reinforced concrete. They transfer the load through weak, compressible material onto more compact, less compressible stiffer soil or rock at greater depth.

Types of Pile Foundation

There are a four main types of pile foundation, each with its own method of construction:

• Driven piles.
• Bored piles.
• Driven and cast-in-situ piles.
• Aggregate piles.

Caisson Pile Construction Method

Caisson construction is a foundation used in deep water or soft soil. It involves a series of large, watertight cylinders that are sunk into the ground and filled with concrete. The base provides a stable foundation for structures built on top of it. Bridges, docks, and large structures often use caisson construction.