High Strain Dynamic Pile Testing

Printer-friendly versionSend to friend
Geo Dynamics is a market leader in this testing and owns sets of Pile Driving Analyzers for assessment of bored / driven concrete and steel piles. We have proven experience of more than a decade in almost all types of pile foundations listed below
  • Cast-in-place bored piles for diameters from 400mm to 1600mm
  • Monitoring of driven pre-cast / pre-stressed concrete piles
  • Testing of Steel H-pile and close / open ended steel pipe piles
  • Driven and Bored Micro Piles
  • Offshore piles for jetties, ports, platforms    

We have done co-relation / reliability studies for almost all these pile types installed in different soil types and using a variety of drop / diesel / hydraulic hammers. Our current data base includes such studies for more than 100 piles and can be obtained on request.
 

HSDPT APPLICATIONS
Dynamic pile testing has been in use in more than 40 countries and is a part of various code specifications worldwide including ASTM 4945. The test can be used to evaluate various pile parameters, few of those important for cast-in-place bored piles are mentioned below.

  • Static capacity of the pile at the time of testing.
  • Static load test curve
  • Total skin friction and end bearing of the pile
  • Estimate of skin friction variation along the length of the pile
  • Compressive and tensile stresses developed in the pile during testing
  • Net and total displacement of the pile.
  • Pile integrity and changes in cross-section if any.  

In addition to above PDA is an extremely efficient tool for driven piles to decide termination criterion, hammer, drop height, efficiency, stresses and other parameters. 

APPLICABLE FOR
Applicable for practically all types of pile foundations includes cast-in-place driven and cast-in-place bored concrete piles, driven pre-cast, pre-stressed spun piles, steel H-piles, pipe piles, micro bored and driven micro piles.

Cannot be used for testing of pile groups and needs a heavy impact to generate forces and velocities and a Pile Driving Analyzer with sensors to measure them.   
 
PRINCIPLE OF TESTING

The basic purpose of high strain dynamic pile testing is to evaluate pile static capacity and its structural integrity using measurement of both force and velocity. Unless, any method uses instrumentation to measure force (or strain) it cannot be called dynamic testing as such, since the basic requirement of the test is to measure dynamic impact and convert it to static capacity.

The method involves attaching a minimum of two pairs of strain transducers and accelerometers on diagonally opposite sides of the pile. These are fixed minimum 1.5 times the pile diameter below pile top & impact generated using a hammer weight equal to 1% to 2% of static test load. Note that it is required that High Strain Dynamic Testing (HSDPT) confirms to ASTM D4945 or other such relevant codes.  

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 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. A more accurate value of these parameters is then obtained from CAPWAP analysis conducted on field data.
 
BENEFITS OF DYNAMIC PILE TESTING

BORED PILES

  •  Significantly faster and economical than static tests; with proper setup arrangements can test atleast 2 bored piles and even more driven piles per day.
  •  Very effective for large diameter bored piles with huge capacity & applicable for both offshore & onshore piling
  •  Applicable to almost all kinds of piles.
  • Reduces or eliminates static load testing especially in case of jetties, flyovers, bridges, multistory buildings where space is a constraint.
  • Provides information on friction, end-bearing, pile integrity, hammer performance and plot simulated load test curve for comparison with static testing.
  • Reduces controversies and eliminates risk enabling a safe foundation.

 
DRIVEN PILES

  • Can be used to decide termination criterion, hammer performance, pile capacity many times instantaneously at site.
  • If problem then it can evaluate whether problem is pile / soil / hammer.
  • Measures driving stresses for effective driving control.
  • Very effective for offshore piles, where conducting static load testing is very difficult.

TECHNICAL PAPERS

caltex
Caltex Jetty Singapore

Mumbai Flyovers
Mumbai Flyovers

India's Longest Railway Bridge at Cochin
India's Longest Railway Bridge at Cochin

Micro Pile Ready for Testing
Micro Pile Ready for Testing

Sensors Fixed On Sides Of Bored Pile
Sensors Fixed On Sides Of Bored Pile

Offshore Testing at Madagascar
 Offshore Testing at Madagascar
Oi Jetty- FQA by Geo Dynamics
 Oil Jetty- FQA by Geo Dynamics

Valid XHTML 1.0 Transitional Powered by : Dots and Coms

Copyright © 2002 - 2010 Geo Dynamics. All rights reserved.