Pile driving is a fundamental technique for constructing buildings, bridges, and other structures. It is a precise, cost-effective approach for driving piles deep into the ground to create foundational support.
However, pile driving doesn’t go as smoothly as we anticipated all the time due to several factors. Numerous issues arise while driving piles into the soil that can damage the piles or affect hammer pile alignment.
In this blog post, you’ll explore the common pile-driving problems and solutions. You’ll also learn about the security measures that can make pile driving safe and effective. So, let’s get into it.
Problem 1: High Blow Count Than Expected
Before starting pile driving, you need to conduct soil analysis. It enables you to determine the number of blows to drive your piles to the desired depth.
However, if the blow count is higher than predicted by soil analysis, there might be some issues with the soil or pile driving system. Sometimes, the problem is with both the soil and your pile-driving system.
To prevent this issue, check your pile’s deliverability. You also need to pay attention to your pile-driving system, as each system is compatible with a particular pile type. You need to ensure their compatibility to prevent this issue.
If compatibility between pile driving system and pile type is not the issue, dig into other issues with the driving system operation. It should comply with the manufacturer’s guidelines.
If you do not observe any of these issues, take dynamic measurements. These measurements will enable you to determine if the problem is soil behavior or the driving system.
- If the issue is with the driving system, you will notice preignition and low hammer efficiency. If the cushion is too soft, it also indicates a problem with your driving system.
- Sometimes, soil resistance increases temporarily with subsequent relaxation, which leads to high blow counts. Another problem that you might encounter is greater soil strength than anticipated. Moreover, high soil damping is another common issue.
Problem 2: Piles Driving Deeper than Expected
Another common issue arises when your piles are driving deeper than estimated. The main reason for this problem is lower soil resistance than you have predicted before pile driving. Sometimes, your pile-driving system works better than your expectation and drives your pile deeper.
To cope with this problem, you need to determine the change in soil strength. You can conduct restrike tests to estimate any fluctuation in soil strength.
If the restrike test shows low capacity, you need to check the performance of the drive system. Dynamic measurements enable you to learn about the restrike capacity and drive system performance.
If you find drive system performance to be the same as predicted and the blow count is low, the issue may be because of weaker soil conditions than estimated.
You need to install the piles deeper than originally estimated. You may need more piles to support the load. You need a structural engineer at this point to alter the design of your project.
Problem 3: Piles are Driving Out of Their Locations
Pile shifting is common at construction sites. However, they shouldn’t be shifted by more than 4 inches from the original spot.
The shifting range is referred to as the tolerance limit. Sifting piles out of their original location is a common problem. It mainly occurs due to soil obstructions or problems with hammer-pile alignment control.
The issue might be because of pile obstruction. In that case, you need to remove the obstruction. According to Nebraska Transportation, removing the obstruction helps resolve this issue when it lies within 3 feet of the working grade.
Suppose the obstruction lies deeper than 3 feet or below the water table. You need to excavate the soil. Spudding or predrilling of pile locations are the most suitable techniques to do this. Poor hammer-pile alignment control can also cause pile shift. A pile gate template or fixed lead can improve it.
Problem 4: Damaging of Concrete Pile Near The Head
Another issue that you might encounter during pile driving is the damage of the concrete pile near the head of the pile. Poor pile quality is a leading cause of this issue.
Poor hammer performance and inaccurate hammer pile alignment also lead to pile spalling. High stress on the pile head is another common reason for the damage to concrete piles.
To resolve this issue, you need to determine pile head stress for observed blow count. You need to compare the head stress with allowable stresses.
If you find stress on the pile head to be higher than allowable stresses, you need to add pile cushioning. If the stresses are low, look for other causes. Poor pile quality, poor hammer performance, or inaccurate hammer pile alignment can also lead to spalling.
Problem 5: Blow Count Lower Than Anticipated
Sometimes, the blow count is lower than you have anticipated during pile driving. It occurs due to low soil resistance or pile breakage below the grade.
To fix this problem, you must reconsider the field procedure and splice detail. Determining these factors will enable you to understand the cause of splice failure. Tensile stresses and compressive stresses at the pile toe are among the crucial aspects.
If they are in the acceptable range, you need to look for some other issues. Obstructions and uneven toe contact on a hard layer can lead to this issue. You also need to pay attention to possible causes of pile toe damage.
Problem 6: Displacement of Previously Installed Piles
Your previously installed piles move. This movement may be caused by soil displacement or soil failure in adjacent layers.
To resolve this issue, you need to retrieve the installed piles or change the sequence of pile installation. Predrilling the pile locations is the best way to reduce ground movement and prevent pile displacement.
Problem 7: Unavailability of Hammer That Meets Driving Stress and Resistance Limits
The compatibility between the hammer and the driving stress and resistance limits is crucial. The unavailability of the right hammer can affect pile driving. This leads to a high value for both calculated stresses. It also results in increased blow counts.
You can resolve it by increasing the pile impedance. Improving material strength can also help you cope with this problem. You can also redesign to achieve lower capacities.
The end-of-driving capacity is kept lower than required if you are dealing with fine-grained soil. Static load and restrike testing can fix the issues with the capacity.
Problem 8: Development of Partial Horizontal Cracks in Concrete Piles in Easy Driving
Sometimes, concrete piles crack horizontally during pile driving. It mostly occurs in hard driving. According to IJARSCT, it happens due to poor hammer-pile alignment, which leads to bending.
Another possible cause of this issue is high combined tension and bending. Pay attention to hammer-pile alignment. If hammer-pile alignment has no issue, check tension and bending.
Problem 9: Driving of Piles Out of Alignment
You might also experience alignment issues during pile driving. It occurs due to insufficient hammer-pile alignment control. Poor soil conditions also lead to this problem.
Soil issues also contribute to this problem. Obstructions near the surface and steeply sloping bedrock with minimal overburden material are the major problems that occur.
You can fix this problem by improving the hammer-pile alignment control. A template, pile gate, or fixed lead system can boost the ability to maintain alignment tolerance.
Security Measures Provide Protection
Here are some security measures that provide protection during pile driving:
- You should wear protective gear, including canvas gloves and goggles. If you are working at a marine site, you should wear a life jacket.
- Keep the working site clean. Clear any unwanted material, debris, or pile remains.
- Place stowed materials in a secure place. Stack them at a safe site or secure them to prevent them from sliding or falling.
- Frequently inspect your rope and cables to ensure they are in good condition. Replace any worn-out rope to prevent accidental falls.
FAQs
1. What are the issues with pile driving?
You can encounter various problems during pile driving. Some common issues include lower or higher blow counts than expected, lateral movement of installed piles, spalling of concrete piles near the head, and piles driving out of the alignment or out of the location.
2. What are the hazards of pile driving?
Hazards during pile driving include poor soil conditions, piles falling, lifting and rigging, excavation collapse, and electrical hazards.
3. What are the causes of failures in pile foundations?
The main causes of pile foundation include lack of adequate boring, inaccurate soil classification, soft strata under the pile tip, inadequate driving formula, and misinterpretation of load.
Conclusion
Pile driving is a common approach for construction. However, several problems are associated with the pile and driving system, making the process challenging. You might encounter higher or lower blow counts than initially predicted, or your piles might drive out of the location.
Resolve them using appropriate solutions. By employing preventive measures and safety protocols, you can ensure smooth pile driving.
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A reliable pile driver is crucial for preventing common problems that arise during pile driving. Everstar offers you high-quality piler drivers that enable you to install the piles at the required depth. Contact us today to get the best pile drivers for your construction project. Our team will help you choose the right tool for your needs.
