DLT - Profound

1 The purpose of Dynamic Load TestingDynamic Load Testing (DLT) is a quick method toevaluate the bearing capacity of a pile for loadssimilar to the design load. It can be used forprefabricated piles, cast-in-place concrete piles,steel piles and wooden piles. DLT is considerablyfaster than static tests and at a fraction of the a Dynamic Load TestAdequate time should be allowed for soilstabilization before testing. To prepare for aDynamic Load Test, sensors are connected to thepile near the pile head. These sensors have acombined function: to measure strain andacceleration. On concrete piles, the sensors are connected to thepile with anchor bolts. On steel piles, the sensorsare bolted to the pile using threaded holes orwelded mounting blocks. Special sensors forunderwater use are also available. All sensors maybe recovered after testing. Once the sensors havebeen connected to the PDA/DLT monitoringsystem, this system can be used to direct the apply a load, an impact ram or a heavy block(drop hammer) is dropped onto the speciallyprepared pile head.

2 The generated compressionwave travels down the pile and reflects from thepile toe upward. This reflected wave containsinformation about the shaft friction, toe resistanceand pile defects. The measured signals areprocessed and automatically stored by thePDA/DLT monitoring system. The data can beretrieved easily for further review, graphicalpresentation or is most suitable for driven piles. For cast-in-place piles, it may be impossible to generate therequired loads, or the stresses can become toohigh, thus damaging the pile. In such cases,Statnamic Load Testing is more PDA/DLT equipmentThe PDA/DLT system, which is used both for PDAand DLT, operates under a Windows environmentand consists of a monitoring system with a harddisk, signal conditioning, combined sensors forstrain and acceleration and cables. The PDA/DLTsoftware for monitoring and reporting includesmany features to further facilitate signalprocessing and PDA/DLT monitoring system has beendesigned for the harsh construction siteenvironment.

3 The reliability of our monitoringsystem is demonstrated daily by hundreds of usersall over the obtained from DLTTo assess the static performance of a foundationpile with DLT, the dynamic pile resistance and therelationship between static and dynamic pileperformance must be determined. If adequate loadtesting has been conducted on similar piles, it ispossible to obtain satisfactory results without acomparative static test. In this case, the followingprocedure is normally each impact loading, the following infor-mation is collected: compression and tension stressDLTD ynamic Load TestingDynamic load testing in the fieldPDA/DLT monitoring systemDLTD ynamic Load Testingin the pile, transferred energy, driving resistance,shaft friction and toe resistance, bending moment,maximum acceleration, pile structural integrityand the extent and location of any signals and other information can bepresented immediately on screen. A selection ofthe available graphs, all presented as a function oftime and scaled in engineering units, include: Measured signals Transferred energy Acceleration, force, velocity and displacement atthe sensor location Force and velocity x impedance Downward travelling waves Upward travelling waves Driving resistance Estimate of static resistanceThe results are presented in either SI or Englishunits and a report generator program allows thepresentation of a field report immediately afterdriving.

4 The system also provides warnings andother "expert advice".Interpretation of test results using SignalMatchingAfter a Dynamic Load Test, the data are analysedusing the DLTWAVE wave equation module ofTNOWAVE. Pile and soil data are modelled and acalculation is carried out using the wave soil models describe the behaviour in terms ofdisplacement, velocity and acceleration functions,using empirical parameters, which depend onknown soil automatic iterative methods, in which theresults of each DLTWAVE analysis are compared tothe actual measured pile behaviour, appropriatedynamic parameters are refined and the shaftresistance, toe resistance and static loaddisplacement behaviour are procedure can be performed automaticallyand is called "Automatic Signal Matching".Advantages of PDA/DLT systemTransducers PDA/DLT system Compact, reliable, water-resistant, combinedacceleration/strain transducers, cables (on reel)and connectors Mounting jig to increase transducer life and forprotection Junction box for easy mounting and storage oftransducer cablesSignal conditioning PDA/DLT Designed and built for maximum reliability anddurability under harsh site conditions Full digital signal processing Automatic Signal Conditioning Lightweight and small for easy handling Battery and AC powered Number of files with digitized signals onlylimited by hard disk capacity Test box to test system functionsSoftware environment PDA/DLT Programmed under Windows environment anddesigned for use by geo-technical engineers Easy installation of software Higher sample rate allowing higher qualitysignal processing Reporting software availableProfound servicesAnnual maintenance contracts are available forPDA/DLT systems that cover regular calibration ofsensors, minor repairs.

5 Cleaning and specialdiscount on loan or their representatives may carry outDLT services on request and users may send signalscausing difficulties by fax or e-mail for expertinterpretation. Dynamic Load Testing is backed by30 years of pile testing experience for clients allover the world, onshore and offshore. DLT isrecognised as an accepted standard for high straindynamic further information: Profound Box 4692740 AL WaddinxveenThe NetherlandsPhone+31 (0) 182 640 964 Fax+31 (0) 182 649 softwareCombined strain-acceleration transducerISO 9001: 2000 CERTIFICATIONACCREDITEDBY THE COUNCILFOR ACCREDITATION