There are a variety of load testing methods to determine suitability of pile systems for projects of every scope and size. Deep foundation construction requires comprehensive planning, and by conducting a proper load test, you can ensure a successful project.
Different job sites will present unique conditions and can require different types of piles and designs.
Different Types of Load Testing
We’re going to explore these different types of load tests that are most commonly found in pile driving projects.
- Axial Compression
- Rate of Penetration
- Low Strain
Standard load tests apply a load at increments of 25% of the designed pile system where the applied load can sustain the rate of settlement is constantly less than .01″ an hour for a period of two hours. Once this has been achieved, additional loads are added until twice the design loads are met. The ultimate capacity of the design load is added in increments of 10% until failure occurs.
Static load tests provide accurate measurements and process how deep foundations react to an applied load. Projects where multiple sizes of piles are required often use static tests. However, they can cause delays if conducted during the design phase of a deep foundation project, and they can come at a higher cost than standard testing.
Axial compressive tests are a quick and straightforward method that is often used in infrastructure projects. These can take up to five hours to perform and are not ideal for soils or clays that require more extended periods to settle for a comprehensive analysis.
Tension tests require a fourteen-day waiting period and offer the direct comparison of compression and tension for the underground profile. Tensile tests can determine uplift capacities and can help engineering teams and contractors focus on seismic design and can be performed more quickly than other static load tests.
The constant rate of penetration applies the load to the pile head and is a time-saving test that can be completed in less than one workday.
Lateral load tests are commonly conducted on projects where vessel and seismic impacts are a factor. A hydraulic piling rig can apply a load that reaches up to 200% of the proposed load.
Statnamic testing reduces the chance of damaging piles and exposes driven and cast-in-place piles to less stress during the testing phase. Low strain tests are useful in determining pile length and integrity. However, it cannot be conducted with steel H-piles or non-concrete piles.
Performing Load Tests
The timing of load tests is an essential factor if you’re planning a pile driving rig rental and can save you considerable costs in the long run. Load tests are performed after a site is made accessible and prepared before they can cause unnecessary interference with other aspects of construction.
Because you have to wait for the results, it’s important to get tests scheduled and develop a timeline and schedule that accurately reflects testing and wait times. Just like a piling rig is an essential component of a successful deep foundation project, load tests are just as critical.
A comprehensive load test will include technical specs and crucial information regarding the type, size, length, and placement of piles. It will also help you determine the capacity of the pile driving rig required to properly install the piles. If you are unsure about what capacity pile driving rig your project needs, you can consult with a local pile driving equipment rental company to confirm availability and equipment specifications.
Because of the technical nature of performing load tests, some contractors and operators prefer to have these handled by specialized third-party companies.
Before you start driving piles, preparing a test pile allows you to ensure the accuracy of the load test. Some recommendations include prepping a driving log for every test pile and adequately marking the test pile in 1′ increments to document penetration. Strict records should be maintained that confirm the penetration under the weight of the hammer.
If you’re using steam, air, or a hydraulic piling rig, you should ensure that adequate pressure is maintained throughout this process. Concrete piles that are cast in place should be tested at six locations and have the concrete mix evaluated for proper mixing ahead of pouring.
If you’re driving pre-cast concrete piles, avoid unnecessary handling or driving until it has been confirmed that the concrete has developed its full strength.
RPI Equipment has more than fifty years of experience renting and selling a full range of pile driving and drilling equipment and can help you identify the proper rig for the job that won’t overstrain piles or provide inadequate driving strength.
With proper planning, contractors can avoid costly delays if load testing is not scheduled in advance. The decision to perform a load test will ensure structural integrity and deep foundations that can support even the most significant load capacities.