What Is Under-Reamed Pile Foundation | Uses of Under-Reamed Piles | Advantages & Disadvantages of Under-Reamed Piles | Application of Under Reamed Piles
The concrete used during under-ream piles should have such a slump of 10-15 cm for concrete in water-free unlined holes drilled. For concrete formwork, the concrete required must have a slump of 15-20 cm with efficient outcomes. M-15 or M-20 concrete with a minimal cement content of 350 or 400 kg/m3 can also be used.
The minimum length of under-ream piles in dense layers of expansive soils ought to be 3.5 m below the surface level.
The diameter of the substrate is holding 2.5 times the diameter of the stem.
The overall vertical spacing here between under-reams is 1.5 times the depth of the under-reams for piles up to 0.3 m in diameter. In large diameter stacks, the spacing can be decreased to 1.25 times the diameter of the stem.
The maximum bulb will be at a minimum size of twice the diameter of the bulb. In the case of vast soils, this depth should never be below 1.75 m ground level.
Generally, the amount of bulbs issued does not exceed 2.
The minimum central distance of the under-ream piles in a group is 1.5 times the diameter of the under-ream and is normally maintained at double the under-ream diameter.
Throughout the case of a pile group with a pile spacing of 2 Du, the size of the group can be assumed to be equal to the amount of the load-carrying strength of the specific piles in the category. Throughout the case of a pile group with such a 1.5 Du pile spacing, the safer load allocated per pile should really be decreased by 10%.
It tends to decrease the vertical settlement as well as the differential settlement.
It has been used as soil appears to expand and shrink response to fluctuations in moisture or the expansive structure of the soil.
A requirement of under-reams or bulbs does have the benefit of increasing the ability of bearings and bulbs.
As the number of bulbs is raised between one and two, the load-carrying capacity of the Under-Reamed Pile is raised.
A requirement of bulbs is of particular benefit for under-reamed bulbs to prevent uplifting and being used as anchors.
The cost benefits of the Under-Reamed Piles are due to the smaller depth of the pile pipe, which means that less concrete is used to replace the excavated material.
In a depth for which components of the soil differ depending on the climatic situation, the under-reamed piles weren’t ideal for waterlogged soil since they seize over by friction.
This batteries require stringent quality control and constant monitoring during production.
Much of the period, Under Reamed Piles, are worked manual using a hand-operated pump. It is also very important to protect the plumbing of the pile since because they're not in the plumbing, the entire load transfer process will shift.
As black cotton soil have properties that grow as it interacts with moisture or water then contract because it is drying off. There might be a risk of cracking in the system due to this factor.
In order to prevent disruption caused by a change in soil depth, the reamed pile is being used.
Often, where the soil base just doesn't have enough bearing space, it is used under reamed piles to maximize the capacity.
Underlying reamed piles are appropriate whenever the water level of sandy soil is large.
It is to be included. Whenever the lifting powers are behaving,
Indian Standard IS code 2911 (Part III) - 1980 includes the design and construction of under-reamed piles with one or more bulbs.
As per the code, the diameter of the bulbs under ream will range from 2 to 3 times the diameter of the stem based on the viability of the construction and design specifications.
The coding indicates a spacing of 1.25 to 1.5 times the lamp diameter for the lamps.
The angle of 45 with such a horizontal angle is suggested for all bulbs underneath. This code specifies mathematical expressions for the calculation of bearing and lifting capacities.
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.
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.
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.
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.
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.
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.
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.