During the construction process, determining the termination point of piles is a crucial task that requires careful consideration. This decision is typically made based on the actual pile termination level, which can vary and is ultimately determined during the drilling process.
Two methods that are commonly used to determine the termination depth of a pile are the pile penetration ratio and chisel energy level. These methods enable the specification of an optimized length for the pile, which is essential for establishing similarity in soil strata. By utilizing these methods, it is possible to ensure that the pile is appropriately designed for the specific soil conditions at the construction site.
What are the Termination Criteria of Pile at Construction Site?
1. Pile Penetration Ratio (PPR) for Rotary Piling
The pile penetration ratio (PPR) is an important factor in ensuring that the desired rock layer is reached during the construction process. This ratio is used to determine the actual termination point of the pile based on the energy requirements of the rotary piling rig for a specified PPR. According to IRC: 78-2014, the PPR represents the energy in ton-meter required to advance the pile bore of 1 m2 cross-sectional area by 1 cm.
Ganpule and Gupte have modified the energy concept to derive an equation for determining the pile termination point using rotary piling. This equation, known as Equation 1, takes into account several factors such as RPM, torque, time duration, pile cross-section area, and pile penetration. The PPR can be calculated using this equation, with typical values observed at a construction site presented in Table-1.
The torque-RPM curve is an important consideration in rotary piling, as increasing resistance to rock cutting can result in a decrease in RPM and an increase in Kelly bar pressure, which requires an increase in torque. Manufacturers of piling equipment may provide the torque-RPM curve specific to their machine, and torque meters can be placed on the control panels of hydraulic rigs to measure the torque.
Table-1: Typical PPR rates for rotary auger piling rig, with Torque 180 kN m and RPM 10
| Pile penetration ratio (PPR) (kN m/m2/cm) | Type of strata | Rate of penetration (cm/min) |
| 500-750 | Soil | 40-60 |
| 750-1500 | Highly weathered rock | 20-40 |
| 1500-3000 | Moderately weathered rock | 10-20 |
| 300-6000 | Slightly weathered breccia | 5-15 |
2. Chiseling Energy Concept
Datye and Karandikar introduced the concept of chiseling energy to determine the termination depth of piles. The response of the underlying rock strata can be estimated using the chisel energy level equation, which takes into account the weight of the chisel, the fall of the chisel per blow, a reduction factor based on various factors such as drag on the chisel and type of muck, the number of blows in a specific duration, the nominal pile cross-sectional area, and the penetration depth into the rock strata in that duration.
The chisel energy response data can be plotted depth-wise and compared with nearby bore logs and the number of hours of chiseling. By optimizing the chiseling effort and ensuring the pile capacity, the pile termination zone can be determined.
FAQs about pile termination depth in construction site
What are the pile termination point criteria?
During the execution of a drilling process, there are two methods that can be used to determine the termination level of piles: the Pile penetration ratio and chisel energy level. These equations are important because the actual pile termination level can fluctuate during the drilling process. It is crucial to determine the termination level of the pile accurately, as an incorrect termination level can lead to issues such as reduced pile capacity and structural failure. Additionally, the termination level of the pile impacts the overall construction cost, as well as the time and effort required to complete the project. Therefore, it is essential to use reliable methods to determine the pile termination level to ensure a successful and cost-effective construction project.
What is pile socket length?
A pile socket length is a term used to describe the depth that a pile-end should be driven into a sound and stable rock or soil layer. The objective of pile driving is to ensure that the pile is securely embedded in the ground, providing a stable foundation for the structure that will be built on top of it.
To achieve this, the pile must be driven deep enough into the ground to reach a layer of rock or soil that is capable of supporting the weight of the structure. The pile socket length is determined based on factors such as the strength of the underlying soil, the size of the pile, and the load requirements of the structure.
It is essential to determine the appropriate pile socket length to avoid problems such as pile settlement, which can lead to structural instability and damage. Additionally, pile driving must be performed with precision to prevent damage to adjacent structures, utilities, or the environment. Therefore, it is crucial to hire experienced engineers and contractors to carry out pile driving work.
How to determine pile socket length?
The statement given is a straightforward equation that relates the length of a pile socket to the diameter of the pile. The length of the pile socket is equal to the diameter of the pile multiplied by one. In other words, the length of the socket is simply equal to the diameter of the pile. This equation provides a simple and convenient way to calculate the length of a pile socket, given the diameter of the pile. By using this formula, engineers and construction workers can ensure that the pile socket is of the correct length to provide adequate support for the structure being built.