Geo Dynamics for the first time in 1998 demonstrated the application of these pile tests (HSDPT) to the Indian deep foundation industry by conducting reliability studies on bored concrete piles for the “55 Flyovers Project” in Mumbai. The method is widely accepted today for testing of bored piles in the country due to our efforts and because of an extensive database of reliability studies for more than 250 bored piles of various diameters in a variety of soil types all over India.
Today, Geo Dynamics is a market leader and pioneer in this testing and owns sets of Pile Driving Analyzers (PDA) for assessment of bored / driven concrete and steel piles. Geo Dynamics now offers turnkey testing all over India including its own sets of guides and hammers (ranging from 1T-50T weights) for concrete bored piles. Geo Dynamics is an accepted authority in India for these expertise based tests and has executed major projects in India for metro rail corporations at Delhi, Mumbai, Nagpur, Bangalore, Chennai, Ahmedabad, highway bridges, marine, power and real estate projects.
We have also executed projects internationally at Mauritius, Madagascar, Jordan, Saudi Arabia, Kuwait, Qatar, Bangladesh, Nigeria, Gabon, Burma, Vietnam etc.
We have proven experience of more than two decades in almost all types of pile foundations listed below:
- Cast-in-place bored piles for diameters varying from 200mm to 2500mm with load ranging from 50T to more than 10000 in variety of soils and rock.
- Driven pre-cast / pre-stressed concrete piles.
- Steel H-pile and close / open ended steel pipe piles upto 2650mm.
- Driven and Bored Micro Piles.
- Offshore piles for jetties, ports, platforms.
High Strain Dynamic Pile Testing Method
The method involves attaching a minimum of two pairs of strain transducers and accelerometers on diagonally opposite sides of the pile. These are fixed at a minimum distance of 1.5 times the pile diameters below the pile top. The testing is conducted by impacting a hammer whose weight is typically 0.7% to 4% of static test load, so that a force normally more than the test load is generated and measured.
Strains induced under the impact of a heavy falling hammer from a pre-determined height are measured with the help of strain transducers attached to the pile, whereas accelerometers record the accelerations generated in the pile. The Pile Driving Analyzer then converts strain to force, and acceleration records are converted to velocities. The resistance developed by the pile is then a function of force and velocity and includes few assumed factors such as the quake and damping parameters as inputs based on the soil type. The maximum pile top compression is obtained by integrating the pile top velocity. The testing is continued by continuously increasing the drop height in stages until the test load is achieved or the pile shows a permanent set of at least 4mm per blow for several blows.
On completion of field testing, the data is subjected to a rigorous CAPWAP analysis. The final output not limited to but generally consists of the following for concrete bored piles.
- Static Capacity at Time of Testing.
- Static Load Test Curve.
- Total Skin Friction and End Bearing.
- Skin Friction Variation along the Pile Length.
- Compressive And Tensile Stresses Developed During Testing.
- Net and Total Displacement of the Pile.
- Pile Integrity And Changes In Cross-Section
Benefits of testing with Geo Dynamics
Geo Dynamics provides complete in-house setup arrangements for dynamic testing ensuring excellent data, more reliability and testing of more than one bored pile per day depending on pile location.
Our large database quickly helps our customers certify acceptable piles and otherwise identify if problem is hammer, pile or soil.
The test replaces static load testing for bored and driven piles. At several projects optimization is done based on the tests results in quick time resulting in large cost and time savings to our customers.
Geo Dynamics also maintains a huge database for testing of spun piles, pre-cast piles and large diameter steel pipe piles in offshore conditions. This enables providing quick estimates of long term and End of Drive capacity estimates, hammer efficiency etc.
High Strain Dynamic Pile Testing Advantages
High Strain Dynamic Testing done by Geo Dynamics is on par with the best worldwide.
Applicable both Offshore & Onshore for Bored, Driven Concrete, Steel, Timber Piles.
Generates useful information other than pile capacity.
More tests can be conducted & hence better-Quality Assurance.
Tests conducted by Independent Agency.
Requires less space compared to Static Tests.
More Safety compared to Static Testing.
Evaluates Pile Integrity Incl. Extent & Location of damage.
Determines if problem is Pile, Soil or Hammer.
Confirms Capacity, Even at Large Loads
Precautions
The method requires significant expertise and understanding of piling methods, equipment’s, installation procedures, soil behaviour and wave mechanics.
Merely having a PDA equipment will not make an expert and engaging untrained or not capable testing companies may lead to dangerous consequences for the project.
Proper care should be exercised while selecting a testing company including background checks, presentations, technical papers, and discussions before high strain dynamic testing is allowed at the project site.
Testing using Hiley formula as done by some companies does not qualify as dynamic testing as it does not conform to ASTM D4945 and neither to IS: 2911 as claimed. The IS: 2911 Part: 3 mentions Hiley formula for capacity calculations for driven piles and not for testing. Results may vary by upto 200% if testing is done using Hiley formula.
Code compliance
Geo Dynamics conducts all tests as per ASTM D4945 – 2016 and IRC:78. Geo Dynamics is also represented on some of the regulatory bodies in India in corporate or individual capacity to form neutral and independent specifications for dynamic pile testing.