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+27 31 701 9732


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Sixteenth Avenue

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+27 11 314 3148

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OUR STAFF ARE AFFILIATED WITH THE FOLLOWING

FREQUENCY RESPONSE AND  PULSE ECHO TESTS (PILE TAPPING)
LAB  Scheduled Rates

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The tests can be implemented on all types of individual cast insitu piles of 250mm diameter and upwards and is a non-intrusive test. The tests are based on locating impedance along the pile shaft by using vibration waves at the top of the pile formed by striking the pile top with an impulse hammer (refer to Figure 1) whilst simultaneously measuring its vibratory response.


When the signal is processed in the time domain the test is called the Sonic Echo Test, and the Frequency Response Test in the frequency domain.  The frequency response graph provides the most comprehensive integrity information whilst the sonic echo tests are only used to complement the information obtained from the frequency response tests on selected piles.  


These tests have a depth limitation, typically 30 to 35 times pile diameter that are usually dependant on soil conditions. The results are then downloaded and computed in the office, and changes in impedance are related to physical features of the pile, taking into account piling methods, material properties and subsoil conditions.  















Prior to carrying out pile tapping the piles will require the following minimum preparation:


* Piles to be trimmed to sound concrete or grout, with a relatively flat  surface perpendicular to the pile axis.  Tests can be carried out when piles are being trimmed to final trim level.  

* All loose debris and surface water to be cleaned off.

* Pile head to be accessible, tests may not be possible with steel in place.


Once an anomaly is identified in the interpretation of the results, further appropriate testing may be carried out.  Where practical the pile is exposed at the approximate depth of the anomaly to confirm the findings of the integrity test.  

  

Recently Geosure using the DIAGNOSTIC PILE ANALYSER identified acoustic anomalies in several piles. On an upmarket development in Durban, Geosure were appointed to carry out integrity tests on all piles cast. 25% of the piles tested showed severe necking in the pile’s shaft.  These piles were exposed to the depths where acoustic anomalies were identified. The adjacent plates show the severity of some of the anomalies identified.


  Pile integrity testing is carried out by Geosure (Pty) Ltd using the     

Diagnostic Pile Analyser supplied by NDT Technology and Piletest.com,            which provides a rapid and relatively inexpensive means of screening groups of piles for  anomalies, which might affect pile performance.  These tests can be usefully implemented on all types of individual cast in-situ piles.  Only limited information may be obtained for secant type piling because of binding between adjacent piles.  Precast piles may be checked for mechanical damaged cracks.  A pile integrity assessment can only be as good as the quality of the test data.  The DIAGNOSTIC PILE ANALYSER is a purpose built system which makes extensive use of the latest digital signal acquisition and data processing techniques to ensure the integrity and quality of the test data.  The Analyser has provision to carry out both Frequency and Sonic Echo test methods on each pile.  The combination of these methods aids the interpretation of complex results and enables difficult assessments to be made with greater confidence and reliability.


Some of the larger projects on which Geosure have carried out Pile Integrity Testing are:




The structural defects in the piles shown in the accompanying photographs were confirmed when exposed by excavation around the pile shafts after anomalies were identified in the integrity test results.


Testing is carried out regularly for the following contractors:


Aveng Grinaker - China Harbour Engineering Company - China Road and Bridge Corporation - Dura Soletanche Bachy - Frankipile – Keller Group - JC Geotechnical Services - Megapile Coastal - Megapile Inland - Pilecon - Siyabora Piling - Stefanutti Stocks Geotechnical Piling - Tshona Piling - Wepex Geotechnical


Over the past 20 years Geosure have invested substantial time and effort in developing pile integrity testing skills in South Africa.  With the support of NDT Technology in the UK, local personnel have been trained abroad to operate the equipment and evaluate test results.  The stature of testing together with the level of skill and experience achieved has established Geosure firmly as the leaders in this field in Southern Africa. At present it is acknowledged that in South Africa, Geosure has developed and pioneered integrity testing to the point where most piling contractors and many consultants accept the test results with confidence.


The integrity testing service offered by Geosure is considered by many contractors and clients in the marketplace to add significant value to piling contracts, particularly as such testing provides a rapid and relatively inexpensive means of screening the structural integrity of all piles on a site, as opposed to testing a select few piles using pile load tests.


Where acoustic anomalies are identified in test results, further investigation of the piles in question may be required

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