Light Weight Deflectometer

The modulus of subgrade reaction (ks), useful for designing flexible foundations, pavements, and slabs, is defined as pressure per unit settlement (kN/m³). While traditionally measured using a 762 mm plate in static Plate Load Testing, the Light Weight Deflectometer (LWD) with a 300 mm plate can also estimate ks. To account for size differences, a correction factor of 2.22 is applied. Accurate results require homogeneous material to a depth of 1.5x the plate diameter. By plotting pressure versus deflection and interpolating to a target settlement of 0.568 mm, ks can be calculated for dynamic field conditions using LWD.

Scope

This Test Method describes the procedure to determine dynamic modulus of deformation of a soil. The test involves the soil receiving an impact of maximum force transmitted through the fall of a drop weight onto a circular load plate of radius r that is assumed to be rigid. Force is selected during calibration, by adjusting the drop height, so the maximum normal stress under the load plate is 0.1 MPa during the test. The resulting deflections are measured at the centre of the top of the load plate. These deflections are used to calculate the dynamic modulus of deformation (Evd).

The data may be used for quality control of compacted layers of earthworks with fine-grained and coarse-grained materials up to a maximum particle size of 63 mm. It is suitable for materials with a dynamic modulus of deformation in the range of 15–70 MPa. It is not a replacement for proof rolling.

This document compares the Light Weight Deflectometer (LWD) Dynamic Deformation Modulus (Evd) with relative dry density or Density Ratio (Dpr) across various soil groups, based on German DIN 18196 and Australian AS1726 classification. While density is a static property representing mass per volume, modulus reflects stiffness and resistance to deformation under load—offering a stronger performance indicator. Although there are generic correlations between Evd and Dpr, these relationships are highly variable and influenced by factors like moisture content, compaction effort, and material type. Tables provide indicative Evd values corresponding to degrees of compaction for different soil types, highlighting LWD’s value in performance-based compaction assessment.

This document outlines how to estimate the Resilient Modulus (Mr)—used in pavement design—from the Dynamic Deformation Modulus (Evd) measured by a Light Weight Deflectometer (LWD). While Evd represents stiffness under a single dynamic load, Mr reflects a material’s response to repeated traffic loading. Due to the high cost and complexity of direct Mr testing, indirect correlations using field tests like the LWD and Plate Load Test (PLT) are explored. These correlations must be used cautiously, as they are affected by factors like moisture content, density, and soil type. The document highlights recent methods such as LWD testing on Proctor-compacted lab samples to define target moduli. It also compares soil classification systems (DIN 18196 and AS1726) and provides tables linking soil types, compaction levels, and expected modulus values. While exact conversions are limited, combining field and lab data can produce reliable estimates for use in quality assurance and pavement design.

This document explores the relationships between various soil strength and stiffness parameters commonly used in geotechnical and pavement engineering: Ev1 and Ev2 (static deformation moduli from Plate Load Tests), Evd (dynamic modulus from the Light Weight Deflectometer), and the California Bearing Ratio (CBR). Each test offers insight into different aspects of soil behaviour, from small-scale material strength to large-scale structural performance. While the CBR test provides a measure of a soil's bearing capacity in a confined mold—primarily at the top 5 mm of the sample—the plate load tests (static or dynamic) assess the performance of a much larger volume of soil, capturing a more holistic view of stiffness under load.

Though no universal mathematical formula links CBR directly with Ev1, Ev2, or Evd, empirical correlations have been established through research, particularly in Germany. Pioneers like Prof. Dr. Weingart and Prof. Dr.-Ing. Floss developed reference tables and graphs suggesting relationships between these parameters for different soil types. For instance, one commonly used approximation is Ev2 ≈ 2 × Evd. These insights support more informed decision-making during earthworks and pavement design.

The satisfactory performance of well-designed pavement sectionshinges on the appropriate compaction of layers in the field, especially compacted geomaterials forming the foundation layers. In-situ spot density tests are standard practice for assessing the compaction effort, even though the mechanistic-empirical design procedures are based on layer moduli. The state of the practice in in-situ density measurements, and more recently modulus measurements, relies on limited in-situ spot testing meant to represent a large area of compacted geo-material. Intelligent compaction (IC) can be utilized to access the as-built moduli by vibratory rollers across the entire compacted geomaterial area to overcome the limitation of spot density tests.

This paper presents an approach to assess the layer-by-layer variation in the as-built moduli. The real-time IC mapping process has proved to be practical, efficient, and robust. The assessment results can be obtained by combining the IC measurement values (ICMV) with limited lightweight deflectometer (LWD) measurements for local calibration and laboratory-based resilient modulus non-linear parameters. The method's veracity and applicability are demonstrated through comprehensive data from two cells collected during the Minnesota Road Research Facility (MnROAD) reconstruction. The assessment results showed that the local in situ calibration of the ICMVs with the limited LWD modulus is necessary to obtain accurate layer-specific as-built moduli.

Industry familiarity with density-based assessment for Quality Control (QC) purposes currently hampers the use of more accurate tests. An ARRB research project identified several alternative quality tests that have the potential to provide improved accuracy (as compared to density). These “new” methods (most are over 20 years old) provide a reduction in both the duration of onsite testing and turnaround of test results and provide the direct measurement of a stiffness (modulus) value. Overall, these alternative tests do not correlate well with the common density ratio (DR) test. Most alternative field equipment tests seem to be positioned between the Plate Load Test (PLT) and density in terms of accuracy and precision. The results and comparisons at the Smithfield Bypass project (approximately 11.5 km North-West of Cairns CBD) is presented. This site was tested in early 2019 and is one of several “live” test sites between 2017 and 2019. Field testing was undertaken upon an embankment being constructed over Avondale Creek and in parallel to standard tests for QC. Lessons learnt and comparisons between equipment at this site are provided. Dendrogram analysis is used to show the relative relationship between tests.

Density has historically satisfied a 1 parameter need in quality control assessment. Other quality parameters are assessed independently. But modulus and performance-based subgrade design aggregates influences such as density, moisture content, material quality, thickness influence, underlying material and equipment used. Comparing density ratio (DR) to other equipment measurements often leads to a poor correlation, since a multivariate relationship is required - Dendrogram analysis is used in this paper to illustrate this inter-relationship. Yet field supervisors often ask for a correlation to provide a linkage with DR as the de facto standard. A higher DR does not necessarily produce a higher strength or modulus – although this is an implicit assumption.

Data from case studies with project trials over a period of 5 years are used to show the density illusion, which impedes the implementation of other modern testing. Issues associated with alternative tests are also discussed. Parallel testing results over several sites collectively indicate both Type I and Type II errors. Using 1-to-1 parallel testing can lead to DR results demonstrating a “pass” whilst LWD (or other tools) assessment could report a “fail” (or vice versa).

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.

The current industry practice relies on the use of in situ dry density ratio (DDR) to control the quality of compaction during the construction of earthworks. The main reason is because the density measurements are relatively easy to undertake during construction, and the parameter itself is precise and with limited variability.

However, this approach has two major disadvantages, namely: (i) the in situ modulus of the layers is not directly measured, and (ii) there is a significant delay between the time of undertaking the DDR measurement and the delivery of the final test results. Such a (routine) delay in the provision of test results can lead to costly rework being required by the contractor if earthworks are found to be non conforming and require remediation after the works have further progressed. To address the above issues, this National Asset Centre of Excellence (NACOE) research project investigated the viability of using alternative testing techniques to control the quality of constructing earthworks.

This five-year study investigated a range of alternative testing devices, such as the light weight deflectometer (LWD), Clegg Hammer and PANDA probe with a focus to evaluate their effectiveness in assessing the quality of the earthworks constructed. A methodology has been developed to adopt the LWD as an alternative QA method. However, the methodology is equally applicable for other similar technologies.

The report presents the final research outcomes to allow the adoption or trialling of this alternative approach in future roadwork construction projects. The final deliverables include the proposed amendments to MRTS04 General Earthworks, and a technical note that details the technical basis and approach.

Appendix A of this report, includes the Queensland Department of Transport and Main Roads (QLD DTMR) Draft Technical Note – Guidance on Use of Light Weight Falling Deflectometers (LWDs) to be Accepted as an Alternative Method for Verification of Earthworks Compaction Requirements – June 2021. This provides guidance on moving from a density based specification for compaction control to a modulus based approach to testing in the field.

The draft technical note provides guidance on implementation of Light Weight Deflectometers as an alternative compaction control method including a flow chart showing key steps for assessment/derivation of equivalent acceptance thresholds for LWD use (in lieu of traditional (density) testing minimum thresholds included in MRTS04 – General Earthworks). We believe this “How to” guide will be very useful for industry on projects across the country.

This is Year 4 of the NACOE project which explores alternative testing to quality assurance pavement and subgrade materials. Year 1 (2016–17) completed a comprehensive literature review of different test methods available. Year 2 (2017–18) undertook equipment comparison testing in Ballina NSW and Rocklea QLD. Year 3 (2018–19) continued carrying out field testing at a major TMR project in Cairns. This year’s primary focus was to finalise the draft testing protocol into a technical note and conduct knowledge transfer activities to present the findings to the wider audience in Queensland and Australia.

Two webinars were presented by the NACOE project team, including presentations from two international speakers. The webinars were focussed on the implementation of the draft testing protocol and provided the road industry with updates of the latest development in the USA and the railway industry in Australia using similar technologies.

A technical note was also developed, which outlines a procedure to adopt Light Weight Deflectometer testing as a quality assurance tool for the construction of pavement layers and subgrade.

Industry’s familiarity with density-based assessments for the quality assurance (QA) of pavement layers and subgrades currently favours conventional density measurements over other field tests that have the potential to better validate design parameters achieved during construction. Although such alternative tests (e.g. Prima 100 LWD, Geogauge or PANDA probe) are not necessarily as precise as conventional density testing, the density test itself has significant limitations.

These limitations include the time required to undertake the tests and its inability to reliably assess the in situ devices evaluated in this report.

The background to Phase 3 of the study is covered in Section 2 which discusses the interim findings from Phases 1 and 2. The field testing and analysis conducted on a live construction site to evaluate the alternatives test method is summarised in Section 3. A proposed technical specification is outlined in Section 4 and conclusions and recommendations are discussed in Section 5.

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.

This overview paper discusses a number of innovative insitu test techniques that could potentially be incorporated into Quality Assurance / Quality Control (QA / QC) for the assessment of near-surface materials during the construction phase of earthworks projects. The limitations of traditional QA test regimes (density-based assessments) and other tests frequently adopted for field assessment during the construction phase of projects (CBR and DCP) are initially discussed, with a critique of the continued use of index tests for such material evaluations provided. A number of alternative test techniques that are capable of rapid, direct insitu measurement of stiffness and strength parameters is made, presenting the Light Falling Weight Deflectometer (LWD), Borehole Shear Test (BST) and Variable Energy Dynamic Cone Penetrometer (PANDA Probe) as viable alternative assessment methods. The insitu parameters provided by these alternative tests can be used to directly evaluate if design parameters are being met onsite and, based on the authors extensive experience using each tool within recent major Australian construction projects, the advantages of using such innovative tools and developing project-specific thresholds for adoption of these tools within a QA / QC test regime, are discussed. Current limitations preventing the widespread implementation of these alternative test techniques are also identified.

Keywords: Compaction, LWD, PANDA Probe, Borehole Shear Tester (BST), Quality Control (QC)

Advanced Methods for Compaction Quality Control Part 2 Question Answers

1. How is moisture ratio taken into account?
2. Modulus is influenced by moisture too; so, shouldn't a comparison should MDD v Modulus include consideration of moisture content?
3. Was the moisture content/ratio taken into account when comparing the Density vs Modulus?
4. The statistical analysis doesn't acknowledge some frustrating variables (1) – e.g. Density Ratio v Modulus not considering moisture content.
5. What was the moisture variations within all the testing?
6. Density Ratio can be performed within 1 day as per AS 1289 5.7.1.
7. Most Victorian testing for earthworks is using rapid HILF method which does not normally require curing if within the test method range.
8. He [the presenter] is referring to assigned value and not the HILF compaction.
9. Are there any case history recorded significant numbers of PLT vs LFWD?
10. PLT has shown vice-versa results and how can we take it PLT as reliability test?
11. The statistical analysis doesn't acknowledge some frustrating variables (2) – e.g. density ratio v CBR not considering material type
12. Embankments need to have a required modulus for strength as well as minimise settlement. Isn't density a measure of minimising settlement and therefore still important?
13. A dry material with low density will have a high modulus, but is this all we care about?
14. Slide 17 – These are awful results and not representative of road construction projects in NSW. What is the source of this data? PS. You are showing density (ratio) results and not quality test results!
15. Slide 19 – One crucial item is the location of the test results, that is layer and GPS / Chainage and Offset! Why is this mixing?
16. Slide 23 – If you are placing and compacting in 300 mm lifts, the LFWD and PLT will not give you reliable results as it influenced by the underlying layers. Therefore, why would you use this equipment?
17. Slide 25 – You have only tested and analysed one formation material. How can you draw any early conclusions?
18. Slide 29 – Work in the USA has shown the portable hand held FWD devices are susceptible to moisture content of the material being tested and have you taken this into consideration to the reliability of the test results from these devices?
19. Slide 50 - You would have to be a brave road agency engineer to allow a contractor to use 1000 mm lifts for embankments with a 18 T padfoot roller!

The Light Weight Deflectometer (LWD) is a portable device that measures the onsite dynamic or resilient modulus (Evd) of subgrade soils and pavements. The LWD, which has been used extensively in Europe and the United States, has become popular for assessing the stiffness of embankments, structural fills and other earth structures. It assesses the bearing capacity, the stiffness and the compaction degree of soils that have a maximum grain size of 63mm. The LWD assessment considers the stiffness (or compressibility) characteristics of the materials under testing to a depth of 600mm below plate level. The paper presents available correlations between 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. It also discusses the fundamental principles behind the testing along with the benefits that may arise from its use on specific applications. Such 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.

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.

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)

Currently, the acceptance of construction works (e.g. earthwork embankments, subgrade and pavement granular layers) by Australian road regulatory bodies requires in situ density testing to be completed in order that a relative percentage of the laboratory-determined maximum dry density can be determined. Current earthworks specifications often rely on the assumption that there is a direct correlation between density and modulus parameters (i.e. the greater the density achieved, the higher the modulus of the compacted material). However, this assumption may not be valid and it is affected by many properties of the engineering material.

Over the last two decades, some alternative field assessment methods have been developed which either directly measure the in situ modulus or correlate with the resilient modulus. This project focuses on exploring the use of these new assessment methods. Such innovative testing methods can be grouped into the following four main categories:

• penetration test devices
• surface based impact devices
• geophysical methods
• in situ sensors.

Among these four categories, the ‘penetration test devices’ and ‘surface based impact devices’ were identified to have the potential to be adopted in TMR’s current Quality Assurance (QA) framework.

A literature review conducted in 2016/2017 highlighted that some similar international studies had been completed in recent years. Recent projects in Australia also demonstrated the advantages associated with these innovative, commercially-available field assessment techniques.

The project team attempted to rank the different QA methods using a weighted rating approach.

The traditional density test techniques were also evaluated as reference values in this assessment. The overall comparative assessment of the different QA test techniques is shown in the following table.

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.

This paper summarizes key findings from QC/QA tests performed on full-scale pavement test sections in a recent Illinois Center for Transportation research study. The focus was to validate newly adopted Illinois DOT material specifications for large size unconventional aggregates, known as aggregate subgrade, through accelerated pavement testing. Seven representative aggregate types were used to construct test sections with aggregate subgrade and virgin and recycled capping and subbase layers. Density measurements from nuclear gauge were collected and routinely contrasted with modulus results of the lightweight deflectometer (LWD) and soil stiffness gauge (GeoGauge) from the constructed layers. Further, forensic strength assessment was carried out by dynamic cone penetrometer and variable energy PANDA penetration device. Geo-endoscopic imaging, coring and trenching were also conducted to identify depth of water table and as-constructed layer thicknesses. The PANDA penetrometer results in conjunction with geo-endoscopy proved to be effective in correlating rutting performances to QC/QA test results.

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.

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

Use of unconventional aggregate materials, such as primary crusher run and concrete demolition waste, have become viable for the construction of pavement working platforms over very weak and often wet subgrade soils. To this end, a research study was undertaken at the Illinois Center for Transportation to evaluate the adequacy and field performances of such large-sized aggregate materials and validate new material specifications.

A state-of-the-art image analysis technique was utilized to characterize the size and morphological properties, e.g. shape, texture and angularity of two large-sized aggregates, referred to herein as primary crusher run and crushed concrete. For the field evaluation, full-scale test sections were constructed with these large-sized aggregate materials over a very weak engineered subgrade and subjected to accelerated pavement testing. Construction quality control was achieved through in-place density and modulus measurements on conventional aggregate capping surface layers using nuclear gauge, lightweight deflectometer and soil stiffness gauge type devices. Periodic rut measurements were carried out on the pavement surface throughout the accelerated loading process using an Accelerated Transportation Loading Assembly (ATLAS). Contributions of the underlying pavement layers to the total rut accumulation was evaluated through innovative applications of ground penetrating radar (GPR), a light weight penetrometer device, known as the French Panda, as well as a geo- endoscopy probe. Layer intermixing and material migration at the aggregate subgrade and subgrade interface was found to improve the layer stiffness and pavement performance results significantly.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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)

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.

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.

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.

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.

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.

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.

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

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.

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.

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

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.

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.

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

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.

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.

Light Weight Deflectometer (LWD) replaces CBR Indicative Graph of Ev2 vs Evd vs CBR

Recommended Values for Road, Rail and Backfill (Static deflection modulus Ev2 (MN/m2), Dynamic deflection modulus Evd (MN/m2) and Compaction ratio Dpr (%) including Deutsche Bahn AG (German Rail) – Quote from Directive 836: “Earthworks Design, Construction and Maintenance” (Ril 836)”, (20.12.1999 a)

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