Pile driving presents numerous challenges as soil conditions can create unforeseen issues during the course of a project. Every project should develop and implement a risk mitigation plan that can identify potential problems to consider common pile driving equipment problems that are frequently encountered. Contingency plans can include solutions that will help avoid costly downtime or scheduling delays.
Every project is sure to have issues, but with a solid plan and the right pile driving equipment, you can overcome these challenges.
Blow Count Calculations and Issues
Blow counts should be calculated in advance based on the soil conditions and your pile driving equipment. If there’s a discrepancy from the estimated blow count in the field, it’s likely there is a problem. One common indicator is increased blows being required to get the pile-driven to the correct depth.
If you are experiencing an increased blow count, ensure that your equipment is operating correctly and according to manufacturer recommendations. Driving system issues can be caused by low hammer efficiency or a pile cushion that is too soft for the pile material.
Soils that are harder than anticipated or have higher damping can also cause increased blow counts. Soil analysis should always be consulted, but in some cases, there are unanticipated conditions that may be encountered once the project kicks off.
If you experience abrupt changes to blow count, you should stop operations and conduct another boring. If you don’t discover evidence of weathered profiles above the bedrock, your pile toe is likely damaged. If you cannot inspect the inside of the pile, you may be able to evaluate the problem with dynamic measurements. In extreme cases, it may require extracting the pile for further inspections.
The two primary causes of a blow count that is slightly lower than expected are less soil resistance or better hammer performance. Perform restrike testing if this is caused by soil conditions, and if low blow counts are caused by hammer performance, you will need to adjust your hammer for lower performance to avoid damaging the piles or equipment.
Spalling and Other Pile Deformation
Chipping or crumbling near a concrete pile head is called spalling and is typically caused by insufficient pile cushioning. This is a relatively simple problem that can be solved by increasing cushioning to accommodate for high stress. Spalling can also be caused by poor pile construction, misalignment, and hammer performance. If you feel your pile driving hammer is underperforming, contact a local service company to perform a thorough analysis of all mechanical systems.
Steel piles can become deformed, while timber piles can split or splinter. This is typically caused by an incorrect helmet size and shape, insufficient steel strength, uneven pile heads, or improper banding.
Shifting and Movement
If piles are showing evidence of unanticipated movement, it can be a significant indicator of serious problems, and work should be stopped immediately to resolve the issue. If there is lateral movement of previously installed piles, soil displacement is likely the cause. The failure of soil in adjacent portions of the site can be remedied by shifting the sequence of pile installation or pre-drilling the earth.
Pile designs allow for a certain amount of alignment tolerance based on the material of the pile, hammer-pile alignment, and soil conditions among other factors. Most operators utilize a template or pile gate to guide the pile into the leader, but if this alignment gets off, it can be caused by an obstruction at the surface. When you remove the obstruction will cause the soil to shift and may reveal additional soil issues underneath. In this case, you will need an analysis by an engineer to evaluate the soil conditions.
Pile Driving Equipment Obstructions
Shallow pile obstructions are considered to be any obstructions found within three feet of the working grade. These can typically be removed without the risk of significantly impacting the surrounding soil or site conditions.
Deep pile obstructions present a more serious obstacle.
In the case of obstructions deeper than three feet of working grade or if they are located below the water table, the best option is to pretrial the pile hole to make for a safe installation that won’t sacrifice structural integrity. Also, this may cause the need for additional pile installation to meet load-bearing capabilities. They can also reduce the calculated bearing capacity, and an engineer should be consulted to redesign the plan.
Pile Driving Equipment Provider
With the right pile driving equipment and collaboration with a trusted vendor like RPI Construction Equipment can help you identify potential issues before they arise. With over fifty years of providing pile rig operators and contractors, we’ve seen it all and have helped our valued clients identify the right equipment for their project so they can deliver the first time.
Our team includes highly talented service technicians that we can deploy to the field to operate on your rig without the need for downtime caused by transporting heavy machinery. They are capable of efficiently servicing your equipment to keep your project on track.