Light Weight Deflectometer (LWD) Zorn ZFG 3000 Overview
Light Weight Deflectometer’s (LWD’s) are a light weight, portable tool used to determine the stiffness of unbound materials (subgrade/subsoils and base layers, granular layers & backfilling materials) or partially bound material (e.g. stabilised) during construction or pavement rehabilitation. For example, for a highway to perform well over the long term, its soil and aggregate layers need to provide a stiff, stable foundation. Inspections are required during construction to ensure that pavement foundation materials have been compacted enough to ensure this condition.
The device measures a deflection and estimates a modulus value based on the force required to generate a given deflection for that soil type. Modulus is the most accurate and independent means for judging deformation (stiffness) and, thus, a material’s level of compaction. By measuring the modulus value, the Light Weight Deflectometer (LWD) provides the direct link between the design specification (design modulus value) and the actual site condition (in-situ modulus value).
The LWD provides immediate repeatable results so that on-site decisions can be made straight away and it can be used in confined spaces and difficult to access locations, with no support equipment required.
The Light Weight Deflectometer (LWD) ZFG 3000 from Zorn Instruments is a compaction control device, according to ASTM E2835-11 (2015). An optional GPS-System allows the user to immediately determine and record the test position and this is integrated with Google Maps.
The Zorn ZFG 3000 equipment measures the dynamic modulus of deformation Evd in the range from 15 up to 105 MN/m². Using extensions to the ZFG 3000, dynamic CBR (California Bearing Ratio) can also be measured in-situ in the field and also laboratory CBR in a cylinder can be simulated.
Experimental investigations show measuring depth with a cone of influence to a maximum of 60 cm.
Site characterisation is unarguably the most important, but also most “difficult”, component of geo-engineering. The Light Weight Deflectometer (LWD) ZFG 3000 is designed to improve the quality of site characterisation and reduce the difficulties involved.
The advantages of the Zorn ZFG 3000 Light Weight Deflectometer (LWD) include:
- Providing a more representative picture of a pavement’s ability to handle traffic loads than laboratory density measurements
- Direct verification of the in-situ modulus values compared to pavement design
- No manual recording of data – results date/time stamped and GPS located so data recording / transposition errors eliminated)
- Results immediately available – no construction delay
- Time saving in testing and getting results (a maximum of 3 minutes per measuring point)
- Immediate connection between ZFG device and iPhone/iPad and Android Smartphones/Tablets
- Results Viewer App for data and graphs – compatible with iPhone/iPad and Android Smartphones/Tablets. Connect GPS data from your ZFG device with Google maps. Send data from your phone to your PC for further analysis and presentation using the ZORN Software
- Data interpretation software allows data storage, analysis and manipulation and easy inclusion into reports
- GPS-System for immediate determination of test position integrated with Google Earth
- Readings captured on SD-card for data memory (10,000 data sets) allowing immediate on-site results printing and data transfer to PC for further analysis
- Provides the link between the Intelligent Compaction (IC) rollers output e.g. the Caterpillar Machine Drive Power (MDP) and the pavement design specification (modulus value) for a specific site so you know that, for example, a MDP of 75 is a modulus value of 42Mn/m2
- No lab work so inspector stays on-site
- Safer for inspectors: Less time kneeling near traffic at a construction site means fewer accidents
- Direct deflection readings: accelerometer directly connected to the base plate
- Accurate repeatable results
- One-person use: designed for field testing, the device is portable and lightweight
- Easy to use
- No additional loading vehicle or support is required
- Using extensions to the ZFG 3000, dynamic CBR (California Bearing Ratio)
can be measured in-situin the field and also laboratory CBR in a cylinder can be simulated.
Applications for this non destructive method for compaction control testing include flexible pavements, unsealed roads and mine access roads, tunnels, railway track beds, airport runway and taxiways, hard standing areas, dam construction, canal building, embankments, mobile crane and piling rig foot standing pads (outriggers), building foundations, wind farms, pipe laying and tank farms.
Clients include those involved in pavement construction, pavement rehabilitation, material testing, geotechnical testing, pavement investigation and site investigation and include road authorities, councils, asset managers, mines, mobile crane operations, engineering and construction groups, EPCM’s, subcontractors, geotechnical consultancies and research organisations. To find out more, Contact Us.
Traditionally the load-carrying capacity of soils is determined by strength tests, such as California Bearing Ratio (CBR) and the static plate bearing test (DIN 18134; similar to BS1377; ASTM D1195, D1196). An improvement on these tests is the dynamic load plate test known as the Light Weight Deflectometer (LWD). The Light Weight Deflectometer (ZFG 3000) is a mobile device designed for compaction control and has been approved by ASTM E2835-11 (2015) Standard Test Method for Measuring Deflections using a Portable Impulse Plate Load Test Device and the German Road and Transport Research Association under TPBF-STB Part B8.3_97.