pile driving monitor (pdm)€¢ the pile driving monitor is a new pile testing device being offered...

Pile Driving Monitor (PDM)

PDM : a transformation in pile driving QA

• Current methods of pile verification – by set card, target set or blow counting are inaccurate flawed and unsafe

• The Pile Driving Monitor is a new pile testing device being offered to industry by AFT and Pile Dynamics Inc.

• The purpose of the PDM is to extend the benefits of PDA testing to every pile across theproject

• It does this by simple, safe and accurate measurements of pile movement and pile velocity

• The PDA and PDM are correlated, and the PDM is then used to monitor the capacity and integrity of every pile

• The PDM is NOT just a set/TC measuring device

© Advanced Foundation Technologies2017

The Equipment


Hardware - PDM Components

EDM(not visible)

PDM Charger

PDM - Tablet USB

Connector Cable

Pile Driving Monitor (PDM)

Target Reflectors


[3] USB connector

[4] Charging connector

[1] Power toggle switch

PDM Rear Face – Main Operational Area

[2] Status lights WiFi Data Power

6


LED Optical Receiver

2 laser positioning pointers (typ)PDM Optics (Front)

• The PDM uses LED technology to scan a section of pile for a high intensity reflection.

• The 4 LED optical transmitters each monitor one section of the active zone.

• A single LED optical receiver collects all signals.

• The lasers are optically safe.

4 LED Optical Transmitters (typ)


EDM Mounting Screw

• A critical input to the PDM is the distance from the PDM unit to the target reflector.

• The Electronic Distance Measurement (EDM) unit is attached securely to the PDM with a standard camera mounting screw

• EDM distance should be recorded to 10mm accuracy

1 : EDM


PDM sand bag

• We recommend the PDM be placed on the ground on the sand bag provided to minimize wind and vibration effects.

Microsoft Surface Pro 4 Tablet

• PDM is controlled by software on a Microsoft Surface Pro 4

• The tablet is supplied with a rugged case

• Wireless connection to PDM unit or USB connection

• Hi visibility screen for field conditions

• Stores full QA records –continuous data signal


Field Set Up


Basic operating principle

Vert

ical

Mo

vem

ent,

V

• The PDM determines the position of the centre of the reflector by the angle in the vertical plane.

• As the reflector moves with the pile motion, the PDM tracks the reflector at about 4000Hz.

• The change in vertical position (pile movement) is computed as ΔV = H. (tan α1-tan α2)

• Measurements are made before the ground wave arrives

α1

α2

Offset Distance, H


Field Setup - 1

1


3

2

• Choose position based on

o Safety;

o Line of sight to target;

o Other sources of vibration;

o Position of sun;

• Place PDM firmly on sand bag in direction of pile

• Typical offset 6m - 12m

Field Setup - 2

6

4


5

• Aim PDM so the active zone (2 red laser dots) is in the midline of the pile and (just) above ground

• Place reflective strip towards the top of the active zone

• Measure the distance to the pile with the supplied EDM

PDM Active Zone

0.5

0m

11.0 m offset

Offset Distance (m)

5.5

10.0

11.0

16.5

20.0

Active Zone Height (m)

0.25

0.45

0.50

0.75

0.90

Approximately horizontal

Act

ive

Zon

eH

eigh


Why are we making these measurements?


• NOT just to measure set and TC

• When we drive and sign off piles we are relying on

1. A reliable relationship between energy, capacity and movement (ECM) for the site or for a group of piles

2. Safe and accurate measurements of movement for every pile

3. An accurate estimate of energy for every pile

Real measurement of movement

• In the US blow counts are measured ‘by eye’ from a distance

• For dynamic formulas, measurement of set and TC is often poor

• The accuracy of capacity estimates is compromised

Hong Kong


Australia Australia

Accuracy of Traditional Set Card Case 2


Accuracy of Traditional Set Card

Pile SP4

Set =14mm/blow

TC = 4mm


Pile SP37

Set =0.9mm/blow

TC = 3mm

Standard PDM Report Output


Computation of DRF

DRF = 1.20 + 0.031*set

• DRF can be predicted in advance by GRLWEAP

• DRF is then back-calculated by correlation with PDA/Capwap


GRLWEAPpredictions PDA/Capwap correlation

pile driving monitor (pdm)€¢ the pile driving monitor is a new pile testing device being offered...

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