Light Weight Deflectometer

Overview

Compaction Control

The Light Weight Deflectometer measures a deflection and calculates a modulus value based on the force required to generate a given deflection. 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 provides the direct link between the design specification (design modulus value) and the actual site condition (in-situ modulus value).
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 sometimes partially bound material (e.g. stabilised) during construction or pavement rehabilitation.

The Zorn LWD’s measures the dynamic modulus of deformation Evd in the range from 15 up to 140 MN/m².

Using extensions to the Zorn LWD’s, dynamic CBR (California Bearing Ratio) can also be measured in-situ in the field and also laboratory CBR in a cylinder can be simulated.

Bearing Capacity

The LWD is used for allowable bearing capacity Quality Assurance (QA) of prepared surfaces, prior to the installation of permanent structures (e.g. slabs, footings, pavements) or temporary works platforms (crane pads, piling rigs). The bearing capacity under the plate is from 30 – 400 kPA, achieved by changing plate diameters, drop weights and drop height.

Let’s take a crane lift. The insitu ground conditions have been identified in order for the temporary works platform to be designed. However, immediately prior to the crane lift, the insitu conditions are required to be verified to determine if the bearing capacity of a site has altered due to changing conditions, like rain. The LWD is used for this purpose.

Light Weight Deflectometers (LWD) from Zorn Instruments

The Light Weight Deflectometer (LWD) ZFG 3000 and ZFG 3.0 from Zorn Instruments are compaction control methods designed to ASTM E2835-11 (2020) Standard Test Method for Measuring Deflections using a Portable Impulse Plate Load Test Device, TPBF-STB Part B8.3 (2016) from the German Road and Transport Research Association (BaST) and Department of Transport and Main Roads Queensland (DTMR) Test Method Q258A Dynamic Modulus of Deformation – Light Falling Weight Device – Accelerometer Type

Applications

The LWD is well suited to in-situ testing of earthworks during construction, particularly where common techniques (e.g. nuclear gauge/sand replacement) are not appropriate or cost effective.
LWD’s are more accurate than the traditional DCP, especially in soft/loose materials or for estimating allowable bearing capacity.
Applications 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, temporary works platforms (crane pads and piling rigs), building foundations (footings and slabs), wind farms, pipe laying, contaminated sites and tank farms.

Advantages

The advantages of the Zorn ZFG Light Weight Deflectometers (LWD’s) include:

Faster

  • Results immediately available so on-site decisions can be made straight away with no construction delay.
  • Immediate wireless connection between LWD and iPhone/iPad and Android Smartphones/Tablets enabling you to send data from your phone to your PC / remote engineering support for further analysis, decision making and presentation using the ZORN Software.
  • Approx 3 minutes per test

More accurate and repeatable

  • Direct deflection readings: accelerometer directly connected to the base plate.
  • High levels of repeatability

Non destructive

  • As a surface based test, the LWD has no footprint that needs to be remediated
  • The surface is not disturbed, which is very important for contaminated sites
  • Granular and geo-reinforced materials can be tested

More representative

Without errors

  • Equipment is instrumented (data is automatically and accurately recorded)
  • Results are machine produced (overcoming manual data recording, transposition or calculation errors and fictitious results)
  • Readings captured on SD-card for data memory (10,000 data sets) allowing immediate on-site results printing and data transfer for further analysis.

GPS located and time stamped – know where and when every test is done

  • GPS-System for immediate determination of test position integrated with Google Maps.

Visually presented results

  • Results including graphical outputs immediately available so integrity of results can be checked
  • Data interpretation software allows data storage, analysis and manipulation and easy inclusion into reports.

Improved safety

  • Less time testing near traffic at the construction site.
  • Suitable for use in confined spaces and difficult to access locations, with no support equipment required.

More cost effective

  • One person operation: portable, lightweight and easy to use.
  • Cost-effective for completion at locations where equipment/plant has to be stopped whilst the test is completed.
  • No additional counter weight vehicle or support is required.

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.

Light Weight Deflecometer Data Viewer
Light-Weight-Deflectometer-LWD-zfg3000-GPS-Zorn

How it Works

Principles of Measuring Compaction

ZFG 3000 LWD Light Weight Deflectometer Rail modulus
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. Light Weight Deflectometer’s (LWD’s) are used to determine the stiffness of unbound materials (subgrade/subsoils and base layers, granular layers and backfilling materials) during construction. The device measures a deflection and estimates a modulus value (Evd) 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 (modulus value) and the actual site condition (modulus value).

Stiffness is the relationship between stress and strain in the elastic range or, in layman’s terms, how well a material is able to return to its original shape and size after being stressed. In general, the more resistant to deformation a subgrade is, the more load it can support before reaching a critical deformation value. Three basic subgrade stiffness/strength characterizations are California Bearing Ratio (CBR), Resistance Value (R-value) and elastic (resilient) modulus. Resilient Modulus (Mr) enjoys widespread use in pavement design.
Light Weight Deflectometer LWD Base Layer Subgrade
Load bearing capacity. The subgrade must be able to support loads transmitted from the pavement structure. This load bearing capacity is often affected by the degree of compaction, moisture content, and soil type. A subgrade that can support a high amount of loading without excessive deformation is considered good.

Sub-grade materials are typically characterized by (1) their resistance to deformation under load, in other words, their stiffness or (2) their bearing capacity, in other words, their strength. In general, the more resistant to deformation a subgrade is, the more load it can support before reaching a critical deformation value.

How the Light Weight Deflectometer Equipment Works Technically

A mechanical impact on a circular steel plate produces a deformation on the soil surface. A light weight is dropped from a standard height and, after release, moves down a rod to a dumping spring that transfers the force to the centre of the load plate.

The load plate contains an accelerometer that measures movement and sends a signal to the control unit. The first integration of acceleration shows the velocity of the plate. And the second integration gives the deflection. The deflection and the velocity of the plate are calculated by double integration of the acceleration. The dynamic deformation modulus is calculated from these results provided that all further parameters like the contact pressure are constant. This simple approximation leads to stable results.

Using the 10kg falling weight, the Light Weight Deflectometer (LWD) measures in the range of 15 -70 MN / m². Using the 15kg falling weight (1.5 times the impact load), the measuring range extends from 70-105 MN / m².

The measuring procedure starts with three pre-loading drops for good contact with the ground. Then, three measuring drops are executed for registration and calculation of the average value and dynamic deformation modulus Evd. The results are stored on a SD-card or printed out directly. With the aid of a SD-card, the data can transferred to a PC.

dynamic deformation modulus stiffness LWD Light Weight Deflectometer

stiffness bearing capacity modulus LWD Light Weight Deflectometer

bild_funktion_02

stiffness bearing capacity modulus LWD Light Weight Deflectometer

  • 1.The print out results are presented in this format:1. Sinking in speed
  • 2. s/v: to evaluate compression
  • 3. Deflection curves
  • 4. Date and time of test
  • 5. Deflections
  • 6. Mean values
  • 7. Evd: dynamic deformation modulus

Thinking behind the LWD Equipment Design

The principle of the Light Weight Deflectometer ZFG 3000 and ZFG 3.0 is based on the principle of a truck loaded with 10 Tonnes driving at 80km / hour and passing over 1 square metre. This is a typical dynamic process and the ZFG 3000 simulates these conditions. Under the rear double tyre, you have a pressure of approx 0.1MN/m2. When the 10kg weight drops on the 300mm diameter plate, you exert the same pressure of 0.1MN/m2 under the plate. (Plate diameter: 300 mm, area 0.07068 m² that means the falling weight must produce a force of 7.068 kN to get 0.1 MN/m²). For the 15kg falling weight, a force of 10.6 kN results in a pressure of 0.15 MN/m² under the plate. The time of this test is given by the spring under the falling weight.

  • 0.1MN/m2 = 10.2 Tonnes over 1 m2

If the test is done on a chip sealed pavement, the chip seal acts like an elastic band, as the binder holds the material together. Hence the results are not as direct / accurate as if the test was done on top of the sub-grade.

Documents

Category

Topic

Publication Date

Reset

TP BF-StB Part B 8.3 Dynamic Plate Load Testing with the Light Drop Weight Tester 2016

Category: Technical Standards

Topic: Germany

Date: 2016

Download

TP BF-StB Part B 8.4 Calibration Rules for the Light and Medium Drop-Weight Tester 2016

Category: Technical Standards

Topic: Germany

Date: 2016

Download

An application of Lightweight Deflectometer Portable Impulse and Variable Energy Dynamic Penetrometer PANDA DCP devices for compliance testing of performance-based rail formation - Blanchett & Doe - ICSMGE 2022

Category: Research Papers

Topic: Rail

Author: Vincent Blanchet, Douglas (Y.W.) Tun, Kelen Marczak Polli, Li-Ang Yang, Andy Doe

Date: 2001

Results of compressive strength and resilient modulus measured in situ using a Variable Energy Dynamic Penetrometer (VEDP) – PANDA DCP, Light Weight Deflectometer – Portable Impulse (LWD-PI), and Plate Load Test (PLT) and laboratory Unconfined Compressive Strength (UCS) during a full-scale trial on the Australian Rail Track Corporation (ARTC) Inland Rail project. These alternative tests reduce the level of laboratory testing effort while the near real time display of results aids in construction time frames which is of particular benefit to projects in remote locations. The methods can be combined with traditional field testing methods to develop site-specific correlations and validate geotechnical parameters assumed in the design.

Download

DESIGN OF RAIL FORMATION AND SUBGRADE – MATCHING TESTING TO DESIGN PARAMETERS - Vincent Blanchet & Andy Doe - Core 2020

Category: Research Papers

Topic: Rail

Author: Andrew Doe , Vincent Blanchet

This study, from the Australian Rail Track Corporation (ARTC) Inland Rail project research, presents the resilient modulus from LWD for capping, structural fill, general fill and at foundation level, together with an example of near real-time reporting of the results using a geospatial platform. The LWD resilient modulus results are compared to cyclic triaxial test results at foundation level as well as Dynamic Cone Penetration (DCP) and Shear Vane Tests (SVT). The results indicate that the LWD may be used in combination with reduced traditional compliance testing frequency to save on time and laboratory testing effort.

Download

Relationship between Field CBR and Dynamic Deflection Modulus for Black Cotton Soil – Landge, Gupta, Patni & Shahare – Visvesvaraya National Institute of Technology, India – IJCIET Vol8, Issue 3, March 2017

Category: Research Papers

Topic: Comparative Studies between the Light Weight Defectometer and other Devices.

Author: Landge, Gupta, Patni & Shahare

Date: March 2017

This study relates dynamic deflection modulus (from the Light Weight Deflectometer) with Field California Bearing Ratio (FCBR). The FCBR test was used to determine CBR on the field to counter practical problems associated with Lab CBR. The test results showed that there is a strong linear correlation between FCBR and Dynamic Deflection Modulus (Evd) for black cotton soil in saturated condition. By using LWD instead of FCBR would result in better quality control, significant cost and time saving.

Download

Test Method Q258A Dynamic Modulus of Deformation - Light Falling Weight Device - Accelerometer Type

Category: Technical Standards

Topic: Australia

Author: Department of Transport and Main Roads

Download

Non-Nuclear Methods for Compaction Control of Unbound Materials – Transportation Research Board – NCHRP 20-05/Topic 44-10 Synthesis 456 – Nazzal – 2014

Category: Research Papers

Topic: Comparative Studies between the Light Weight Defectometer and other Devices.

Author: Munir Nazzal

Date: 2014

This report synthesizes knowledge on national and international experiences and practices using non-nuclear devices and methods for compaction control of unbound materials. This includes:

Types of compaction control testing devices used by state DOTs, including construction specifications;
Non-nuclear devices that have been evaluated by state DOTs and those under consideration, including proposed specifications;
Various types of non-nuclear devices available and comparison of these devices with nuclear devices;
Correlation of non-nuclear device measurement results to material properties (e.g., density, modulus, stiffness, moisture content);
Issues with non-nuclear devices, such as accuracy, precision, ease of use, reliability of data, safety, test time, level of expertise required, Global Positioning System compatibility, calibration, durability, costs, and compatibility with various unbound materials; and
The advantages, disadvantages, and limitations of the various compaction control devices.
Indiana and Minnesota DOTs have widely implemented stiffness and strength-based specifications for compaction control using DCP and LWD measurements.

Download

Characterisation of in-situ soils based on the resilient soil modulus obtained using Light Weight Deflectometer (LWD) – N.Barounis & T.Smith – New Zealand Geotechnical Society – Nov 2017

Category: Research Papers

Topic: Flexible Pavements and Rigid Pavements

Author: N Barounis, T Smith

Date: November 2017

The paper presents available correlations between dynamic or resilient modulus (Evd) with the static soil modulus Ev obtained from static plate load tests. It also presents how Evd can be linked with CBR and thus be useful for pavement design, but also with the subgrade reaction modulus K of the assessed soils. Applications include the design and construction monitoring of gravel rafts, the design of pavements, engineered and non-engineered fills, landfills, MSE walls, pipelines and services, evaluation of ground improvement effectiveness and soil stiffness mapping.

Download

Use of the Lightweight Deflectometer (LWD) at Highland Valley Copper Mine - Singh, Mejia, Martison and Shah (KCB Vancouver), Fleming and Fitzpatrick (Teck Highland Valley Copper Partnership, Logan Lake, BC, Canada) - GEO2010

Category: Research Papers

Topic: Mining

Author: Neil K. Singh, Carlos Mejia, Tracy Martison, Farhat Shah, Chris Fleming, and Joseph Fitzpatrick

Date: 2010

Use of the LWD at the L-L Tailings Dam, the ore stockpile cover foundations, fuel tank station, and at the multiplate overpass foundations and backfill. A comparison of the LWD capabilities with alternative field testing measures is presented along with an evaluation of its effectiveness at Highland Valley Copper Mine.

Download

ZFG 2000 Understanding Results Paper – Prof. Dr. Ing. W. Weingart – 2005

Category: Research Papers

Topic: Understanding the Light Weight Deflectometer (LWD) and its Results

Author: Prof. Dr. Ing. W. Weingart

Date: 17 April 2005

How to understand accelerometer based Light Weight Deflectometer graphical and numerical results

Download

Foamed Asphalt Stabilized Base – A Case Study – Khosravifar, Schwartz & Goulias – University of Maryland – 2013

Category: Research Papers

Topic: Flexible Pavements and Rigid Pavements

Author: Sadaf Khosravifar, Dimitrios Goulias

Date: 2013

The primary objective of the project was to evaluate the suitability of using Foamed asphalt stabilized base (FASB) in high traffic volume pavements and to assess its fundamental engineering properties. FASB density, moisture content and hydraulic properties were evaluated in the field and its stiffness was monitored as the material dried and cured during the first week and at 4 to 6 months after placement. Field tests included nuclear moisture and density gauge readings, permeability assessment, and stiffness measurements using a lightweight deflectometer (LWD), a GeoGauge, and a falling weight deflectometer (FWD). Of particular interest was the increase in stiffness of the FASB with time during curing and the comparison of this increase with that observed in a companion GAB control section at the site.

Download

Final Report

Category: Research Papers

Topic: Flexible Pavements and Rigid Pavements

Author: Soheil Nazarian, PhD, PE, Mehran Mazari, PhD, and Imad Abdallah, PhD, Anand J. Puppala, PhD, PE, Louay N. Mohammad, PhD and Murad Y Abu-Farsakh, PhD

Date: August 2014

The objective of this research was to develop a modulus-based construction specification for acceptance of compacted geomaterials that considers the following constraints:

The specification should be based on field measurement of modulus and moisture content.
Acceptance criteria should be correlated with design moduli.
The specification should be compatible with a variety of compacted geomaterials.
The specification should consider the principles of unsaturated soil mechanics.
Available models, devices, and methods should be incorporated in the specification.
The validity and practicality of the proposed specification should be documented by its use as a shadow specification for a number of actual construction projects.

Download

Using the Dynamic Cone Penetrometer and Light Weight Deflectometer for Construction Quality Assurance – Minnesota DOT – 2009

Category: Research Papers

Topic: Flexible Pavements and Rigid Pavements

Author: John Siekmeier, Cassandra Pinta, Scott Merth, Julie Jensen, Peter Davich, Felipe Camargo, Matthew Beyer

Date: 2009

Specification target values for granular materials and fine grained soils are proposed. For granular material, the grading number and field moisture content are used to select the dynamic cone penetrometer (DCP) and light weight deflectometer (LWD) target values. A sieve analysis is used to determine the grading number and an oven dry test to determine the field moisture content. For compacted fine grained soil, the plastic limit and field moisture content are used to determine the target values. The plastic limit is used to classify the soil and to estimate the optimum moisture content for compaction.

The DCP and LWD estimate the strength and modulus of compacted materials. More specifically, they measure the penetration and deflection. When measuring penetration and deflection, the moisture content remains a critical quality control parameter for all compaction operations. Therefore, the moisture content needs to be measured, or estimated confidently, at each location. The LWD and DCP are performance related construction quality assurance tests that are expected to: increase compaction uniformity, lower life cycle pavement costs, increase inspector presence at the construction site, improve documentation, and increase inspector safety and productivity.

Download

Intelligent Compaction Implementation: Research Assessment – University of Minnesota (July 2008)

Category: Research Papers

Topic: Intelligent Compaction and In-Situ Testing (Stiffness Control)

Author: Joseph F. Labuz, Bojan Guzina, Lev Khazanovich

Date: July 2008

IC provides only an index, which is specific to the conditions associated with a particular site. An interpretation of comments provided the basis for the following recommendations:

  • Use light weight deflectometers (LWD) for quality assurance of stiffness
  • Establish a procedure to determine the target LWD value
  • Eliminate calibration areas (control strips)
  • Simplify IC data evaluation and presentation
  • Calibrate the IC roller and related transducers
  • Support development of alternative IC methodologies
  • Simplify or eliminate moisture corrections
Download

Application of the Modern Method Embankment Compaction Control – Bailystok Techical University – Poland (Sept 2003)

Category: Research Papers

Topic: Flexible Pavements and Rigid Pavements, Rail

Author: Maria Jolanta Sulewska

Date: 17 May 2004

Light drop-weight tester is a device for field tests and it is used for quick control of bearing capacity and compaction quality of built-in soils in different types of embankments. It is a modern device which is commonly used in Germany and now in Poland. The examples of calibration of the light drop-weight tester in laboratory and in-situ,
and its application in real embankment are presented.

Download

Geotechnical Studies for the Adelaide Rail Revitalisation Project – Comparing In-Situ and Laboratory Testing of Ballast & Subgrade Materials – Parsons Brinckerhoff Mark Drechsler & Chad Parken – Railway Engineering Conference Sept 2010

Category: Research Papers

Topic: Rail

Author: Mark Drechsler, Chad Parken

The South Australian Department for Transport, Energy and Infrastructure (DTEI) commissioned Parsons Brinckerhoff (PB) to undertake geotechnical and environmental investigations over 104 km of rail network to provide information on track and drainage conditions and contamination levels of ballast and subgrade materials for the track reconstruction works.

The paper presents details of the investigative methods undertaken to collect and present the data, compares laboratory tests with in-situ test results, describes the main causes for track stability problems and recommends potential design and construction solutions.

Laboratory tests were undertaken on ballast and subgrade samples and included soaked and unsoaked California Bearing Ratio (CBR), total suction, and soil and pavement material classification tests. In-situ testing included pocket penetrometers, Dynamic Cone Penetration (DCP), Clegg Hammer, Light Weight Falling Weight Deflectometer (LWFWD) and Humboldt GeoGauge stiffness test methods.

PB recommended the LWFWD for inclusion into DTEI standard specifications for railway construction works.

Download

Validation & Refinement of Chemical Stabilization Procededures for Pavement Subgrade comparing Dynamic Cone Penetrometer (DCP), the PANDA penetrometer, and the Portable Falling Weight Deflectometer (PFWD) – Miller, Cerato, Snethen, Holderby & Boodagh – Oklahoma Department of Transport (Oct 2011)

Category: Research Papers

Topic: Flexible Pavements and Rigid Pavements, Pavement, Backfill and Working Platforms

Author: Miller, Cerato, Snethen, Holderby & Boodagh

Date: October 2011

This study compared results of field tests and laboratory tests on chemically stabilized soil at different curing times to assess whether a relationship exists between field and laboratory measurements. The goal was to determine if a field testing method could be used to assess whether the strength and stiffness in the field are consistent with laboratory measurements used for design.

Field testing included three devices that are portable, quick, and easy to use. These devices include: the Dynamic Cone Penetrometer (DCP), the PANDA penetrometer, and the Portable Falling Weight Deflectometer (PFWD). Laboratory testing was conducted to determine the unconfined compressive strength (UCS) and resilient modulus (MR) of laboratory specimens prepared using additive contents that were similar to samples taken from field test locations.

Correlations were examined and involved basic soil measurements (mineralogical, electrical, chemical and index properties) and mechanical properties (UCS and MR), and field test results (DCP, PANDA, and PFWD). The strongest trend was observed for the PFWD – MR comparison. The trend showed that both the PFWD modulus and MR increase with increasing curing time, as expected. These observations show that development of correlations between field and laboratory test results holds promise. However, development of such correlations will require that field and laboratory tests be performed on nearly identical soils and under identical curing conditions.

Download

Grading & Base Manual – Light Weight Deflectometer Procedure & Target Value Determination – Minnesota DOT – March 2016

Category: Technical Standards

Topic: USA State Department of Transport’s

Author: Minnesota Department of Transportation

Date: 3/18/2016

Download

Intelligent Compaction for Soils and Subbase Materials – US DOT FHWA (US Department of Transport Federal Highway Authority) – Transportation Pooled Fund Program Summary

Category: Research Papers

Topic: Intelligent Compaction and In-Situ Testing (Stiffness Control)

Author: George Chang and Qinwu Xu

Five single drum IC rollers (smooth drum and padfoot) were assessed from Bomag USA, Case/Ammann, Caterpillar, Dynapac, Sakai America, and Volvo.

For IC correlation analysis, in-situ tests are used to directly obtain the response of the compacted materials under various loading situations and drainage/moisture conditions. Recommended in-situ test devices for soils/ subbase/ stabilized IC are as followings:

Light Weight Deflectometer (LWD)
Dynamic Cone Penetrometer (DCP)
Calibrated Nuclear Moisture-Density Gauge for soils and subbase (NG)
Falling Weight Deflectometer (FWD)
Static Plate Loading Test (PLT)

Download

US DOT FHWA Accelerated Implementation of Intelligent Compaction Technology for Embankment Subgrade Soils, Aggregate Base, and Asphalt Pavement Materials – Final Report – July 2011

Category: Research Papers

Topic: Intelligent Compaction and In-Situ Testing (Stiffness Control)

Author: George Chang, Qinwu Xu, and Jennifer Rutledge, Bob Horan, Larry Michael, David White and Pavana Vennapusa

Date: July 2011

The goals of this three year project included:

  1. Demonstration of soils/subbase and Hot Mix Asphalt (HMA) IC technologies to department of transportation (DOT) personnel, contractors, etc.,
  2. Develop an experienced and knowledgeable IC expertise base within DOT,
    Assisting DOT in the development of IC quality control (QC) specifications for the subgrade, subbase, and HMA pavement materials, and
  3. Identification and prioritization of needed improvements and further research for IC equipment and data analysis.
  4. Identification and prioritization of needed improvements and further research for IC equipment and data analysis.

Goal No. 1 was accomplished by demonstrating the abilities of the IC system such as: tracking roller passes, HMA surface temperatures, and intelligent compaction measurement values (ICMV).

Goal No. 2 was accomplished by building the IC knowledge base with extensive field experiences, data, and analysis/reports from diverse demonstration projects.

Goal No. 3 was accomplished by training DOT personnel and earthwork/paving contractors on the IC technologies via field demonstrations and open house activities. Continuous support was provided to the TPF State DOTs for the development of local, customized IC specifications during the project period.

Goal No. 4 was accomplished by compiling a comprehensive list of recommendations for the IC roller vendors to further improve their systems for widespread use of the technologies. Various IC systems were reviewed in-depth and gaps were identified for future research and engineering practices.

Download

Best Practice in Compaction QA for Pavement and Subgrade Materials Year 1 Report Jeffrey Lee, David Lacey & Burk Look NACOE P60 QLD DTMR, Australia Aug 2017

Category: Research Papers

Topic: Comparative Studies – PANDA® vs other Compaction Control Methods, Comparative Studies between the Light Weight Defectometer and other Devices., Comparative Studies between the Plate Load Test (PLT) and other Devices

Author: Jeffrey Lee, David Lacey, Burt Look

Date: 30 August 2017

Download

Implementation of Unsaturated Soil Mechanics during Pavement Construction QA John Siekmeier Article

Category: Research Papers

Topic: Flexible Pavements and Rigid Pavements

Author: John Siekmeier

Date: March 2011

Moduli and deflection target values (TVs) for the unbound pavement foundation materials have been proposed for use during pavement design. These TVs are estimated using the plastic limit (PL) for cohesive soils because the PL has been found to be a reasonably accurate predictor of the Soil Water Characteristic Curve (SWCC). Therefore, a family of SWCCs has been defined based on the PL. TVs are then verified during construction of the unbound pavement foundation using the lightweight deflectometer (LWD). Although the deflection values from LWD testing can be suitable to assess the performance of compacted soils, MnDOT has coupled the LWD response with laboratory resilient modulus testing and soil suction measurement to improve interpretation of the results.

Download

Modelling of Dynamic Load Plate Test with LWD (Vienna University of Technology, Austria) – 2003

Category: Research Papers

Topic: Understanding the Light Weight Deflectometer (LWD) and its Results

Author: C. Adam, D. Adam

Date: 2003

Mechanical modelling of the dynamic load plate test with the Light Falling Weight Device (LFWD) is presented. The LFWD is employed on construction sites to verify the compaction degree of soil layers and to evaluate their bearing capacity. The mechanical models developed are intended to provide simple and efficient formulations, which allow a large number of numerical simulations at low expenses. The motion of the device is characterized by a mass- spring-dashpot system. Several one-dimensional linear and nonlinear representations of the soil are discussed and evaluated. Different phases of motion of the LFWD – soil interaction system are identified, and corresponding formulations of the equations of motion are given. In appendices efficient solution procedures of the governing equations of motion are proposed.

Download

PFWD, CBR and DCP Evaluation of Lateritic Subgrades of Dakshina Kannada, India – 2008

Category: Research Papers

Topic: Comparative Studies between the Light Weight Defectometer and other Devices.

Author: Ch. Nageshwar Rao, Varghese George, and R. Shivashankar

Date: 1-6 October, 2008

The performance of pavements depends to a large extent on the strength and stiffness of the subgrades. Among the various methods of evaluating the subgrade strength, the use of portable falling weight deflectometers (PFWD) is gaining popularity in the recent years. This is due to its simplicity in design, portability, and the added advantages of providing quick and reliable estimates of the Young’s modulus of elasticity of pavement subgrades.

This study developed correlations between PFWD results and those obtained using the traditional approaches such as the California bearing ratio (CBR) test and the dynamic cone penetrometer (DCP) test. Regression models were developed as part of this study to enable the prediction of CBR values based on the average of observed values of the Young’s modulus obtained using the PFWD (Epfwd), and prediction of Epfwd from the average penetration-rates of DCPs performed for field density, and field-moisture content.

Download

Influence of Lightweight Deflectometer Characteristics on Deflection Measurement – D. Stamp. and M. Mooney – ASTM Geotechnical Testing Journal, Vol. 36, No. 2, pp. 216–226 – 2013

Category: Research Papers

Topic: Understanding the Light Weight Deflectometer (LWD) and its Results

Author: David H. Stamp, Michael A. Mooney

Date: 2013

The Light Weight Deflectometer (LWD) is currently not standardized; as a result, there are a number of commercially available LWD designs that yield different deflection and elastic modulus values. This proves problematic because transportation agencies are beginning to prescribe target deflections and/or elastic modulus values during earthwork construction.

This paper presents the results of a comprehensive investigation into the influence of LWD design characteristics on measured deflection. The influence of the sensor type (accelerometer versus geo- phone), sensing configuration (measurement of plate versus ground surface), LWD rigidity, and applied load pulse were investigated through field testing and finite element analysis. The investigation revealed that the sensing configuration (i.e., the measurement of plate versus ground surface response) is the predominant cause of differences between the Zorn and Prima LWD responses (deflection normalized by peak force). Vertical plate deflection exceeded ground surface deflection by 65 % to 310 % on soils and by 20 % on asphalt. The relative influences of the sensor type (accelerometer versus geophone), plate rigidity, and load pulse each led to relatively small differences (<10 %) between Zorn and Prima LWD responses. The results of this investigation illustrate that each of the two LWD configurations will always produce different deflection and elastic modulus values for the same ground conditions, and that the differences will be difficult to predict.

Download

Field Validation of Intelligent Compaction Monitoring Technology for Unbound Materials – Iowa State University (2007)

Category: Research Papers

Topic: Intelligent Compaction and In-Situ Testing (Stiffness Control)

Author: David J. White, Ph.D., Pavana K R. Vennapusa, Mark J. Thompson

Date: April 2007

The objective of this research project was to evaluate intelligent compaction (IC) monitoring technology for use in earthwork construction for purposes of quality control and assurance. The following research tasks were established for the study:

  • Develop relationships between roller-integrated and in situ compaction measurements, including dry unit weight, dynamic cone penetration (DCP) index, Clegg impact value (CIV), and light weight deflectometer (LWD) modulus.
  • Characterize measurement variation observed for the various measure- ment systems.
    Identify the influences of compaction energy and method on laboratory moisture-density relationships.
  • Characterize laboratory resilient modulus in terms of soil type, stress state conditions, moisture content, and density.
  • Develop QC/QA guidelines for incorporating roller-integrated compac- tion monitoring technology into soil compaction specifications.
Download

Standardizing Lightweight Deflectometer Measurements for Compaction QA and Modulus Determination in Unbound Bases and Subgrades – Schwartz, Afsharikia, Khosravifar – Maryland DOT – University of Maryland – Sept 2017

Category: Research Papers

Topic: Flexible Pavements and Rigid Pavements

Author: Dr. Charles W. Schwartz, Zahra Afsharikia, Dr. Sadaf Khosravifar

Date: September 2017

Includes AASHTO Drafts:

Standard Method of Test for Laboratory Determination of Target Modulus Using Light-Weight Deflectometer (LWD) Drops on Compacted Proctor Mold – AASHTO Designation: TP 123-01 (2017)

Standard Method of Test for Compaction Quality Control Using Light Weight Deflectometer (LWD) – AASHTO Designation: TP 456-01 (2017)

Download

Geotechnical investigation of a French conventional railway track-bed for maintenance purposes – Lamas-Lopez, Cui, Costa D’Aguiar, Calon – SNCF – Soils and Foundations – Japanese Geotechnical Society Dec 2015

Category: Research Papers

Topic: Rail

Author: F. Lamas-Lopez, Y.J. Cui, S. Costa D'Auilar, N. Calon

Date: 17 December 2015

A comparison of two methods of determining the stiffness of track-bed materials (dynamic penetration and dynamic plate load) comparing the PANDA / PANDOSCOPE and the Light Weight Deflectometer.

Download

Reliability in the Testing & Assessing of Piling Work Platforms

Category: Research Papers

Topic: Temporary Works Platforms – Mobile Crane Pad and Piling Rig Working Platforms

Author: Fred Fountain, Tony Suckling

Date: November 2012

Proposed protocol for testing and assessing of piling work platforms using Ground Penetrating Radar (GRP) and the Light Weight Deflectometer (LWD)

Download

Investigation of the Dynamic Plate Load Test with Light-Weight Deflectometer using the Boundary Element Method (Kopf, Adam & Paulmichl) 2005

Category: Research Papers

Topic: Understanding the Light Weight Deflectometer (LWD) and its Results

Author: Fritz KOPF, Dietmar ADAM, Ivan PAULMICHL

The dynamic plate loading test using the Light-Weight Deflectometer is an innovative field test designed to determine the dynamic deformation modulus of subsoils and fills in all types of earth working and ground engineering applications. In earth working, the test can be used for compaction control and for assessing the load-bearing capacity of the subsoil.

This article compares the results of numerical investigations on the Light-Weight Deflectometer obtained with the boundary element method against results from experimental tests.

Download

Proctor Density, Evd & Ev2 Comparison (Sand & Gravel)

Category: Technical Standards

Topic: Germany

Date: 19 August 2004

Download

Recommended Values for Road, Rail and Backfill (Static deflection modulus Ev2 (MN/m2), Dynamic deflection modulus Evd (MN/m2) and Compaction ratio Dpr (%)

Category: Technical Standards

Topic: Germany

including Deutsche Bahn AG (German Rail) – Quote from Directive 836: “Earthworks Design, Construction and Maintenance” (Ril 836)”, (20.12.1999 a)

Download

The Effect of Water Content on Light Weight Deflectometer Measurements – University of Deleware – Tehrani & Meehan – 2010

Category: Research Papers

Topic: Understanding the Light Weight Deflectometer (LWD) and its Results

Author: Faraz S. Tehrani, Christopher L. Meehan

Date: February 2010

Water content is one of the most important properties that affects the modulus measurements of compacted soil. To explore the sensitivity of measured modulus-based in-situ test results to the effect of compaction water content, a field study was performed in the State of Delaware in the summer of 2008. Two Light Weight Deflectometers (LWDs) were used in the study to measure compacted soil modulus values, one with a 300 mm contact plate diameter and one with a 200 mm plate diameter. The fill material tested during this study was a poorly graded sand with silt (SP-SM). This paper demonstrates the sensitivity of the measured soil modulus values to fluctuation in soil moisture content in the field, and discusses possible approaches for interpreting this type of variable LWD data.

Download

Performance Testing Of Unbound Materials Within The Pavement Foundation – Scott Wilson Pavement Engineering for UK Highways Agency – 2010

Category: Research Papers

Topic: Flexible Pavements and Rigid Pavements

Author: B. Rahimzadeh, M. Jones, B. Hakim and N. Thom - Scott Wilson Pavement Engineering for UK Highways Agency

Date: 2010

Pavement design requires knowledge of the performance of the foundation layers. The specific condition at a given site can be considered in the design; such as the use of locally available material, recycled or secondary aggregate in the pavement foundation, provided the specified end-product performance requirements are achieved.

Performance testing is required in order to ensure that the design assumptions for the material properties are met during construction. Both the capping and sub-base layers need to attain adequate strength and stiffness. Therefore there is a need to undertake complimentary compliance testing that would include target values based on the behaviour of the materials.

This paper describes the research into the development of performance testing for foundation layers based on case studies performed by Scott Wilson Pavement Engineering (SWPE). The performance testing was carried out by Falling Weight Deflectometer (FWD), German Dynamic Plate (GDP) and Prima 100. The results using these test methods were compared and correlated.

The results indicated that the relationships between FWD, GDP and Prima were material type and thickness dependent. The Prima usually gave broadly similar results to the FWD, but was significantly more variable from point to point. The GDP almost always gave a lower stiffness than the other devices, but to varying degrees.

Download

Working Platforms – To BRE or not to BRE is the question – Burt Look Foundation Specialists Group (Brisbane, Australia) and Neil Honeyfield Port of Brisbane (Brisbane, Australia) AGS Journal – 2016

Category: Research Papers

Topic: Temporary Works Platforms – Mobile Crane Pad and Piling Rig Working Platforms

Author: Burt Look and Neil Honeyfield

Date: March 2016

The Building Research Establishment (BRE) produced a practice guide for working platforms for tracked plant, which has become a “standard” in the industry in the absence of any other widely published simple design method. The BRE design method does not apply for thick platforms or for soft subgrades, but continues to be used in those applications in the absence of an alternative document. A case study is discussed which applies the BRE in such a situation, but then compares with alternative methods (including the Light Weight Deflectometer) to assess the required working platform.

Download

Indicative Graph of Ev2 vs Evd vs CBR

Category: Technical Standards

Topic: Germany

Download

Apprendices

Category: Research Papers

Topic: Flexible Pavements and Rigid Pavements

Date: August 2014

The objective of this research was to develop a modulus-based construction specification for acceptance of compacted geomaterials that considers the following constraints:

The specification should be based on field measurement of modulus and moisture content.
Acceptance criteria should be correlated with design moduli.
The specification should be compatible with a variety of compacted geomaterials.
The specification should consider the principles of unsaturated soil mechanics.
Available models, devices, and methods should be incorporated in the specification.
The validity and practicality of the proposed specification should be documented by its use as a shadow specification for a number of actual construction projects.

Download

NACOE Advanced Methods for Compaction Quality Control – June 2018 Webinar – Part 1 (Webinar Slides)

Category: Research Papers

Topic: Comparative Studies – PANDA® vs other Compaction Control Methods, Comparative Studies between the Light Weight Defectometer and other Devices., Comparative Studies between the Plate Load Test (PLT) and other Devices

Author: Jeffrey Lee, Burt Look, David Lacey

Date: June 2018

Download

Deflection Measurement Of Soils Using A Lightweight Deflectometer (LWD) – Modified Ndr Standard Test Method T 2835 – ASTM Designation: E 2835 – Nebraska DOT- 2014

Category: Technical Standards

Topic: USA State Department of Transport’s

Date: 2014

Download

Network Rail BOMAG Report RevG Roller Compaction Trials

Category: Research Papers

Topic: Rail

Author: Paul Strange

Trial to test the Bomag Vario 213 roller’s ability to suitably consolidate bottom ballast for a railway environment, and additionally, to compare methods of measuring the achieved stiffness, including the Light Drop Weight Tester and Plate Bearing Test.

Download

Unsaturated Soil Mechanics Implementation During Pavement Construction Quality Assurance John Siekmeier, Minnesota Department of Transportation – 21st Annual CTS Transportation Research Conference – April 27-28, 2010

Category: Research Papers

Topic: Flexible Pavements and Rigid Pavements

Country of Origin: United States

Date: 27-28 April 2010

Compaction equipment and field tests are now available that can measure the properties used to design pavements and predict performance.

LWDs and DCPs can be used during construction quality assurance to efficiently verify design target values.
Several options exist to quantify moisture and more field measurement devices are coming.
The time is now to accelerate implementation of performance based quality assurance so that our investments are well spent.

Download

PILOT LIGHT WEIGHT DEFLECTOMETER (LWD) DEFLECTION METHOD (2105 or 2106 Excavation and Embankment) – Minnesota DOT – Nov 2011

Category: Technical Standards

Topic: USA State Department of Transport’s

Date: 11 May 2011

Download

Field Determination of Deflection Using Light Weight Deflectometer ITM No. 508-12T – Indiana DOT – Nov 2012

Category: Technical Standards

Topic: USA State Department of Transport’s

Date: November 2010

Download

Advanced Methods for Compaction Quality Control Part 2 Question Answers

Category: Research Papers

Topic: Comparative Studies – PANDA® vs other Compaction Control Methods, Comparative Studies between the Light Weight Defectometer and other Devices., Comparative Studies between the Plate Load Test (PLT) and other Devices

Author: Jeffrey Lee, Burt Look, David Lacey

Download

NACOE Advanced Methods for Compaction Quality Control June 2018 webinar part 2

Category: Research Papers

Topic: Comparative Studies – PANDA® vs other Compaction Control Methods, Comparative Studies between the Light Weight Defectometer and other Devices., Comparative Studies between the Plate Load Test (PLT) and other Devices

Author: Jeffrey Lee, Burt Look, David Lacey

Date: 6/1/2018

Download

Advanced Methods for Compaction Quality Control

Category: Research Papers

Topic: Comparative Studies – PANDA® vs other Compaction Control Methods, Comparative Studies between the Light Weight Defectometer and other Devices.

Download

Best Practice in Compaction QA for Pavement and Subgrade Materials NACOE P60 Year 3 Report Lee, Lacey, Look & Tarr June 2020

Category: Research Papers

Topic: Comparative Studies – PANDA® vs other Compaction Control Methods, Comparative Studies between the Light Weight Defectometer and other Devices., Comparative Studies between the Plate Load Test (PLT) and other Devices

Author: Jeffrey Lee, David Lacey, Burt Look, Kyle Tarr

Date: June 2020

Download

Collation of German Road & Rail Standards for the Light Weight Deflectometer (LWD) including:

Category: Technical Standards

Topic: Germany

Date: 1997

Supplementary Technical Terms and Conditions of Contract and Guidelines for Earthworks in Road Construction ZTVE-StB 94

Supplementary Technical Terms and Conditions of Contract and Guidelines for Excavations and Digging-up in Traffic Areas ZTVA-StB 97

Deutsche Bahn – Guideline to Using the Lightweight Drop-Weight Tester in Railway Construction NGT 39

Download

Comparison of Ev2 and Evd for different materials & pavement types

Category: Technical Standards

Topic: Germany

Download

Additional Information

Density vs Modulus

Current earthworks specifications often rely on the assumption that there is a direct correlation between density and modulus (i.e. the greater the density achieved, the higher the modulus of the compacted material). As a result, existing specifications often require that either the sand replacement test or Nuclear Density Gauge (NDG) test be conducted to demonstrate that adequate density was achieved within the earthwork layers. However, the assumptions used when converting density to modulus have been shown to be highly idealised, and they can be affected by the properties of the compacted fill, subgrade or base material. More importantly, testing has shown that a higher density does not necessarily indicate a higher strength or modulus (Mooney et al. 2003, Mooney et al. 2010).

Issues with a reliance on density testing and CBR results for QA purposes include:

  • Lag indicators – Several days / one week typical to complete. Contractor typically continues work and advances fill placement above the lift – before QA results are available. If non-conforming QA test results are then made available, there are significant costs associated with removing and replacing both the non-conforming material and the overlying material that has been placed whilst the contractor was waiting for the results.
  • Density Oversize correction – This applies when greater than 20% of material exceeds 19 mm or 38 mm for Mould A and B size, respectively. This is not consistently being applied across the industry, with a recent study showing that 22% of 235 samples examined not applying that correction.
  • Strength and modulus parameters – geotechnical and pavement designs are based on strength and modulus values. It is assumed during the design stage that a relationship exists between density and strength/modulus even though density is neither a strength nor a modulus parameter. The simple correlation between CBR and modulus (E) (e.g. E = 10 x CBR) often used in design is generic and there is a significant correlation error associated with its use.
  • The CBR test is not applicable when more than 20% of the material is retained on the 19 mm sieve. Such material is often discarded as part of the test according to the Australian Standards. Differences in material preparation Road Authority Standards would result in different CBR test values being determined and reported.

For more details on these issues, check out the latest research.

Modulus is the most accurate and independent means for judging deformation (stiffness) and, thus, a materials level of compaction. Modern geotechnical and pavement designs are based on in-situ modulus values.

However, the current state of practice is to base the field-testing parameter selection on the result of a non-deformation parameter, such as DCP or CBR results from site investigation or density/moisture relationships in earthworks QA.

This means that there is currently a disconnect between design and construction control.

The Light Weight Deflectometer (LWD) addresses this gap. By measuring the modulus value, the Light Weight Deflectometer provides the direct link between the design specification (design modulus value) and the actual site condition (in-situ modulus value).

The LWD enables one to:

(a) reliably provide a direct measure of the strength or insitu modulus value; and

(b) offers significant time savings in turnaround time of QA test results.

Blogs

Light Weight Deflectomer Local Calibration and Repairs – Announcing Insitutek Trilab Partnership

September 28th, 2022

Belle Panganiban

As well as selling and renting Light Weight Deflectometer to clients, we are delighted to announce a partnership between Insitutek and Trilab for Zorn Instruments Light Weight Deflectometer (LWD) calibrations and repairs. Insitutek clients now have exclusive access to the only Light Weight Deflectometer calibration and maintenance facility in the Southern Hemisphere. Our Australian based Zorn Calibration Stand and Maintenance Facility in Brisbane is exclusive to Zorn Instruments clients and […]

Read More

Guidance On Use Of Light Weight Falling Deflectometers (LWDs) – June 2021

May 28th, 2022

Belle Panganiban

National Asset Centre of Excellence (NACOE), a collaboration of Queensland Department of Transport and Main Roads and the Australian Road Research Board (ARRB), has released their final report for the Best practice in compaction quality assurance for pavement and subgrade materials – P60 project. Importantly, in Appendix A of this report, is the Draft Technical Note – Guidance on Use of Light Weight […]

Read More

Australia’s first Light Weight Deflectometer (LWD) standard released

November 9th, 2020

Belle Panganiban

We are very happy to let you know that Australia now has it’s own Light Weight Deflectometer (LWD) standard. Test Method Q726B: Deflections – Portable Impulse Plate Load Test Device Our Zorn LWDs are fully compliant with Q726B. The standard has been developed by Department of Transport and Main Roads Queensland (DTMR) and is based on the ASTM […]

Read More
Plate Load Test Pacific Complete W2B

Assessment of Compaction Quality Control Methods – NACOE Best Practice Research

June 12th, 2020

Robin Power

The acceptance of earthwork and unbound pavement construction in Australia currently relies mostly on density testing and CBRs for Quality Assurance (QA). Though its National Asset Centre of Excellence (NACoE) research program, Queensland’s Department of Transport & Main Roads sponsored a vital ARRB research project to update test methods acceptable for use for QA of pavement and subgrade […]

Read More
Alternative Testing Methods for Quality Assurance NACoE Light Weight Deflectometer PANDA DCP Clegg

Alternative Testing Methods for Quality Assurance – ARRB Research

June 5th, 2018

Robin Power

The acceptance of earthwork and unbound pavement construction in Australia currently relies on density testing and CBRs for Quality Assurance (QA). Though its National Asset Centre of Excellence (NACoE) research program, Queensland Main Roads has sponsored an ARRB research project to update test methods acceptable for use for QA of pavement and subgrade materials including […]

Read More

Changing Face of Compaction & Compaction Control for Road Building

July 8th, 2015

Robin Power

Changing Face of Compaction & Compaction Control for Road Building – A Global Review Compaction is one of the most important processes in roadway construction. A uniform base and subgrade is a key ingredient in maximising pavement performance and the stiffness is a major contributor to this uniformity, whether it is in pavements, road embankments or […]

Read More

Compaction – The Building Block Of Quality Infrastructure

June 30th, 2015

Robin Power

Compaction – The Building Block Of Quality Infrastructure Earth Mover & Civil Contractor Magazine – Compaction Feature – Jun 2015 Article on getting compaction right first time, with tools like Intelligent Compaction and the Light Weight Deflectometer (LWD).

Read More

Videos

ZORN Light Weight Deflectometer Calibration Process

Light Weight Deflectometer LWD ASTM E2835-11 for Compaction Control from Zorn Instruments

Credentials

Credentials for ZFG 3000 from Zorn Instruments

The Zorn Instruments ZFG-series production started in 1990 and more than 10,000 units have been sold around the world. To find out more, Contact Us.

The ZFG series of Light Weight Deflectometers (LWD) has become widely used and accepted across Europe and internationally in the United States, China, Russia, New Zealand and Australia to name a few.

Zorn Light Weight Deflectometers (LWD) are designed and manufactured in Germany.

The manufacturer is: Zorn Instruments, Benzstrasse 1, D-39576 Stendal Germany www.zorn-instruments.de

Zorn Instruments Logo

Light Weight Deflectometer ZFG 3000 LWD Zorn Rail Compaction ControlLight Weight Deflectometer ZFG 3000 LWD Zorn Bridge Abutment Compaction Control

FAQ

A “wiggling” sign was observed in the tip of the curves. What does this mean?

The wiggling shows that the material is VERY hard and the wiggling is like a vibration of the plate because of the hardness of the material (like a hammer hitting a piece of steel when you can feel the vibration).

How do stiffness values correlate with density?

Typically, stiffness values measured with the Light Weight Deflectometer (LWD) correlate poorly with density. Fundamentally, soil density and stiffness are two very different physical properties.

Density is a static behavior depending on grain density, grain size distribution etc. Density is of a measure of volume.

Stiffness is similar to bearing capacity or deformation modulus and is a measure over a given area.

Further, to meaningfully compare measurement methods, one must ensure the compacted area is homogeneous. This means that at every measuring point, the conditions must be the same material properties, moisture, grain size, thickness of layers, materials etc.

In the “Statistic Dyn” spreadsheet, what does the value Q represents?

This is based on the required minimum you set (Required minimum quantile:) and is a calculated value Q(Evd) = (Arithmetic average of spot-check Xm(Evd) – Required minimum quantile) / Standard deviation s (Evd)

The test (Q>0,88) has failed. This comment identifies whether the test is within acceptable parameters compared with what you have specified (e.g. 25 MN/m²) or not. Again, it’s a calculated value.

What is Evd?

Evd is the dynamic deformation modulus (also known as the dynamic deformation module, dynamic modulus of deformation, dynamic stiffness modulus, composite stiffness, effective stiffness or surface modulus). Modulus is the most accurate and independent means for judging deformation and, thus, a material’s level of compaction. Evd is used to measure bearing capacity and compaction quality for subsoil’s and subgrade materials, unbound base layers, granular layers, backfilling materials, soil stabilisation with lime, cold recycling materials and pavements, cycle tracks and footpaths.

The soil receives an impact of maximum force Fs transmitted through the fall of the drop weight onto a circular plate of radius r, which is assumed to be rigid. When the device is calibrated, the force is selected such that the maximum normal stress σ under the load plate is 0.1MN/m2.

To calculate Evd, the deformability of the soil under a vertical load, as described above, with a settlement amplitude s (in mm) and the duration of impact ts:

Evd (MN/m2) = 1.5 x r x σ /s

For the 10kg drop weight and 300mm diameter plate Evd = 22.5/s
For the 15kg drop weight and 300mm diameter plate Evd = 33.75/s

What is s/v and why is it important?

s/v is a measure of the degree of compaction of soil. The ZFG 3000 has an acceleration sensor attached to the base plate. The first integration of acceleration shows the velocity of the plate. And the second integration gives the deflection.

If the value of s/v is lower than 3.5 ms means: soil is compacted and it is possible to compact to higher compaction.
If the value s/v is higher than 3.5 ms: incompact like in-situ soil or if after compaction, it is not possible to compact to higher values.
The value of 3.5 ms is an empirical value, resulting from practical experience. In contrast to the static load plate, you get more information on the properties of the soil from dynamic load plate test.

What is the maximum grain size that can be tested?

The test procedure is suited, in particular, for coarse-grained and mixed-grained soils wth a maximum grain size of 63mm. For aggregate, bedding sand is used to ensure complete contact between the base plate and the surface being measured.

What is the relationship between Evd and Ev2?

The relationship between the static deflection modulus Ev2, measured by the static plate bearing test, and the dynamic deflection modulus Evd depends on the kind of soil and the degree of compaction.

Experience shows that the ratio Ev2/Evd lies in the range 1.0 to 4.

For densely compacted soils Ev2/Evd ~ 2.3

On average the following relation between the dynamic deflection modulus Evd, and the static deflection modulus Ev2, can be used:

This relation does not hold for limiting values.

What is the relationship between stiffness and field moisture content?

Typically, there is close relationship between the stiffness values measured with the Light Weight Deflectometer (LWD) and the field moisture content. The influence of moisture is much higher because of the capillary effect of water so the results are sensitive to insitu field moisture.

The optimum moisture from the Proctor Test will yield the best results, as one would expect. Every sand and gravel mixture has an optimum water content depending on grain size distribution.

What other names is the Light Weight Deflectometer also known by?

Deflection survey
Deflection testing
Deflection test method
Drop weight tester
Dynamic Light Drop Weight Tester
dynamic plate test
dynamic load plate test
dynamic plate load test
Falling Weight Deflectometer
FWD
FWD-Light
German dynamic plate
Impulse deflection testing
Light Falling Weight Deflectometer
Light FWD
Light Weight Deflectometer
Light Drop Weight
Light Drop Tester
Light Drop Weight Tester
LDWT
Light Weight Hammer Drop Tester
Light Weight Deflectometer
LWD
Load deflection test
Load plate test
Portable Falling Weight Deflectometer
Portable FWD
PFWD
Portable Light Weight Deflectometer
Portable LWD
PLWD
ZFG2000
ZFG 2000
ZFG02
ZFG 02
ZFG3000
ZFG 3000
ZFG 3000 GPS
ZFG 3000 ECO
ZFG3000 GPS
ZFG3000 ECO
Zorn

Trusted by our clients

View
View
Sydney Trains Logo
View
Coffey
View
View
View
Queensland Government
View
BHP
View
View
View
View
Progress Rail Logo
View
View
Fulton Hogan logo
View
Australian Geotechnical Testing Logo
View
View
SGS
View
LRPardo and associates
View
Golder Associates logo
View
Construction-Sciences
View
ATC Williams
View
View
Geotechnical-Testing-Services
View
FSG Geotechnics + Foundations logo
View
downer
View
Fletcher
View
Road Science logo
View
Civil Innovation Logo
View
Global Synthetics Logo
View
SMEC logo
View
Tailcon Projects logo
View
4D Geotechnics Logo
View
Chadwick Geotechnics Logo
View
View
A&Y Associates Logo
View
Ground Science Logo
View
Tasman Geotechnics logo
View
Bloxam Burnett Olliver
View
CPTS Logo Cone Penetration Testing Services
View
CivilTest Logo
View

Our Supply Partners:

Anix Logo
View
AP van Den Berg Logo
View
View
Sol Solution Logo
View
Zorn Instruments Logo
View

Insitutek Blogs

Insitutek: Building a Better World Through Sustainable Civil Construction Practices as a Certified B Corp

April 4th, 2023

Belle Panganiban

We see a huge opportunity for business to balance profits for shareholders with the well-being of people and the planet and we are actively encouraging our client base to think in a similar way. The global B Corp community is made up of companies building an economy that is not only sustainable but also inclusive […]

Read More

AGS Queensland Annual Symposium 2022

December 2nd, 2022

Belle Panganiban

The AGS Queensland Annual Symposium was held on 29 Nov 2022 in Brisbane. Our exhibition stand was manned by Robin Power who had conversations with many of the 160 attendees. Recent advance in geotechnical engineering, engineering geology, and testing was the theme for the Australian Geomechanics Society (AGS) Queensland Chapter Symposium. The program included:

Read More

A Reliable Methodology for the Determination of the Modulus of Subgrade Reaction – Case Study

November 28th, 2022

Belle Panganiban

Engineers appear to be fixated on soil bearing capacity as the fundamental soil parameter for foundation design worldwide, with the assumption that the footing will behave as a rigid body. This assumption is usually not applicable for large and multi-column foundations, and in such conditions, engineers prefer flexible analysis using numerous available software. These computer […]

Read More