Academic literature on the topic 'Light Falling Weight Deflectometer (LFWD)'

In the mechanistic design approach, which has already been started to utilize in several countries, the variations in material properties are better taken into account based on fundemental engineering principles. Resilient modulus is the most important material property that is used in the mechanistic design since it describes the true martial performance of unbound pavement layers under traffic loading. In this thesis, the objective is to determine the resilient modulus, used in the mechanistic design of pavement structures, for the unbound material types used in Turkey and develop linear and nonlinear prediction models to determine resilient response of unbound layers based on soil index properties, California Bearing Ratio (CBR) and Light Falling Weight Deflectometer (LFWD) test results. Application of genetic algorithm and curve shifting methodology to estimate design resilient modulus at various stress states is also investigated using the test results for finegrained soils. Resilient modulus estimation for a constant stress state based on genetic algorithm and curve shifting methodolgy is quite promising for fine-grained soils since nonlinear constitutive models do not have the capability of representing resilient responses under different conditions. Furthermore, tree-based modeling is discussed as an alternative way to develop resilient modulus prediction models. The outcome of the study will be a basis for the performance based design specifications of flexible pavements.

A series of large-scale pavement model tests were conducted in a laboratory environment to investigate the effect of geosynthetics in improving the modulus of weak subgrades. Then, a series of supplement design charts that could be useful for industry practitioners to design geosynthetic reinforced flexible pavements were developed. The outcomes of this study promote the use of geosynthetics in road construction to make economical, environmentally friendly, climate resilient, and sustainable road infrastructure.

The Light Falling Weight Deflectometer (LFWD) is a dynamic non-destructive test developed to estimate the in-situ stiffness modulus of pavement materials. The technology of this device is very similar to that of the Falling Weight Deflectometer (FWD) to most closely simulate the loading rate and area of a single moving wheel. The LFWD is a portable scaled down hand operated version of the mechanical electrical FWD that applies an impulse load from a drop weight impacting a circular plate resting on the surface to impose various contact pressures through a calibrated system of rubber buffers. The LFWD, like the FWD, measures both the force and deflections with a velocity transducer to calculate the stiffness of the particular layer. Over the past decade the LFWD has experienced increased popularity due to the fact that non-destructive tests can be undertaken to determine aspects of a constructed layer s engineering and physical properties and because it is portable. The LFWD would ideally be used to provide better engineering parameters for the quality assurance and quality control during the construction of granular and lightly cemented layers. Previous LFWD research consists of correlation studies between different strength characterisation testing equipment of pavement layers, there is however, a lot of variability present in these correlation relationships. One of the most prominent sources of engendering variability within the LFWD measurements is attributed to inconsistent operation protocol. This study was undertaken to establish an operation protocol for the Dynatest 3031 LFWD device and to consequently investigate the influence of various parameters on the surface moduli and deflection bowl parameters yielded by the LFWD and to determine a reliable relationship between LFWD stiffness results, deflection bowl parameters and other pavement material parameters. The ensuing intention is to accurately predict the model or monitor the basic material characteristics and enhance standard construction quality control testing in a practical engineering quality control application. LFWD deflection bowl benchmark analysis in conjunction with the calculated surface modulus values can effectively be used as a first step screening tool in identifying areas or zones of distress in a newly constructed pavement layer. The concept of the well-known Red, Amber, Green (RAG) structural condition rating system have been utilised for the LFWD derived deflection bowl parameters and proposed surface moduli ranges for granular base pavements. This study confirms that the LFWD can be utilised as a non-destructive quality control testing device in a practical engineering quality control application. In spite of the lack of exactness of the current RAG criteria, it had been experienced that such a high sample density non-destructive test method and benchmarking can help identify areas or spots in a constructed layer which warrants additional conventional testing. Additional research is however necessary to continuously improve and revise the proposed ranges in order to achieve accurate and reliable flexible pavement quality and acceptance control procedures for the LFWD device.<br>Die Ligte Vallende Gewig Deflektometer (LVGD) is 'n dinamiese nie-destruktiewe toetsapparaat wat ontwikkel is om die in-situ styfheid modulus van plaveisel materiale te bepaal. Die tegnologie van hierdie toestel is soortgelyk aan dié van die Vallende Gewig Deflektometer (VGD) om die belading en kontakdruk van 'n enkele bewegende wiel akkuraat te simuleer. Die LVGD is 'n draagbare, afgeskaalde handgekontroleerde weergawe van die meganiese elektriese VGD wat 'n impulslas toepas van n vallende gewig op n ronde plaat wat op die oppervlak rus, impakteer om ? kontakdruk oor te dra op die plaveisel deur 'n gekalibreerde stelsel van rubber buffers. Die LVGD, soos die VGD, meet beide die kontakdruk en defleksies met 'n versnellingsmeter om die styfheid van n bepaalde laag te kan bereken. Gedurende die afgelope dekade het die LVGD toenemende gewildheid ervaar te danke aan die feit dat draagbare nie-destruktiewe toetse gedoen kan word om aspekte te bepaal van n gekonstrueerde laag se ingenieurs en fisiese eienskappe. Die LVGD sou ideaal gebruik word om beter ingenieurs-parameters vir die kwalitiet konstruksie kontrole beheer te verskaf tydens die konstruksie van klip en gruis-materiaal en ligte gestabiliseerde plaveisellae. Vorige LVGD navorsing bestaan uit korrelasiestudies tussen verskillende sterkte karakteriserings toetstoerusting van die plaveisellae. Daar is egter baie variasie teenwoordig in hierdie korrelasie verwantskappe. Een van die mees prominente bronne van variasie binne die LVGD meetings word toegeskryf aan teenstrydige operasionele protokol tydens toetsing. Hierdie studie is onderneem om 'n operasionele protokol te vestig vir die Dynatest 3031 LVGD toestel en om gevolglik die invloed van verskeie parameters op die oppervlakmoduli en defleksiekom parameters wat opgelewer word deur die LVGD te ondersoek. Dit het 'n betroubare verhouding tussen LVGD styfheid resultate, defleksiekom parameters en ander plaveisel materiaal parameters daar gestel. Die daaropvolgende voorneme is om die basiese materiaal eienskappe met behulp van 'n model akkuraat te voorspel of te kan moniteer. en om as eerste orde aanduider toetse gebruik te word met standaard konstruksie kontrole beheertoetsing in 'n praktiese ingenieurswese kontrole beheer omgewing. LVGD defleksiekom parameters maatstaf of relatiewe ontleding in samewerking met die berekende oppervlakmodulus waardes kan effektief gebruik word as 'n eerste orde keuringsinstrument in die identifisering van gebiede of sones van swakker materiaal kwaliteit in 'n nuut gekonstrueerde plaveisellaag. Die konsep van die bekende relatiewe maatstaf met Rooi, Amber, Groen (RAG) strukturele toestand graderingstelsel is gebruik, en kriteria voorgestel vir die LVGD afgeleide defleksiekom parameters en voorgestelde oppervlakmoduli vir klip en gruis-materiaal of korrelmateriaal kroonlaag plaveisels se strukturele sterkte evaluering. Hierdie studie bevestig dat die LVGD benut kan word as 'n nie-destruktiewe konstruksiekontrole beheertoetsing apparaat in 'n praktiese konstruksiekontrole beheer omgewing. Ten spyte van die gebrek aan akkuraatheid van die huidige RAG kriteria, is dit ervaar dat so 'n hoë frekwensie toets potensiaal, nie-destruktiewe toets metode kan help om areas of kolle in 'n gekonstrueerde laag te identifiseer wat bykomende konvensionele toetse regverdig. Verdere navorsing is egter noodsaaklik om voortdurend die voorgestelde evalueringskriteria te verbeter en te hersien om akkurate en betroubare buigsame plaveisel kwaliteit en aanvaarding beheer prosedures vir die LVGD toestel daar te stel.<br>Dissertation (MEng)--University of Pretoria, 2016.<br>tm2016<br>Civil Engineering<br>MEng<br>Unrestricted

Dissertação de mestrado integrado em Engenharia Civil<br>Nas últimas décadas, a rede rodoviária nacional sofreu um grande desenvolvimento tanto ao nível das infraestruturas existentes, como na construção de novas vias. Este desenvolvimento implica também a uma preocupação crescente na conservação e reabilitação da rede. Assim, de forma a aferir-se a verdadeira necessidade da sua reabilitação dos pavimentos existentes, é necessário realizar-se a avaliação da sua capacidade de carga, que é obtida com base em vários parâmetros tais como a deflexão, que por sua vez permite determinar o módulo de deformabilidade das camadas dos pavimentos. A medição das deflexões em pavimentos rodoviários pode ser feita recorrendo a vários métodos, uns mais eficientes e modernos que outros. Esta dissertação centra-se então no estudo e comparação dos métodos mais utilizados na avaliação da capacidade de carga de pavimentos rodoviários, onde são medidas as deflexões com quatro métodos distintos, em vários pavimentos com constituições diferentes entre si. Durante as medições utilizam-se os mesmos procedimentos de ensaio para cada um dos métodos em estudo. Com os valores das deflexões obtidos em cada um dos pavimentos e com cada método, são analisados e comparados os dados entre si, obtendo-se assim, expressões que traduzem as relações das deflexões medidas entre os vários métodos. Um dos equipamentos com maior interesse em ser estudado neste trabalho é o Defletómetro de Impacto Ligeiro (Light Falling Weight Deflectometer, LFWD), para o qual é feita uma comparação adicional com o Defletómetro de Impacto convencional (FWD), noutro local, com o objetivo de apurar com maior rigor a relações existentes entre as deflexões medidas com os dois equipamentos, comparando-os também com a literatura existente.<br>During the last decades, the national highway system suffered a major development, both of the existing infrastructures and of construction of new roads. This development also implies a growing concern in the maintenance and rehabilitation of the highway system. Thus, in order to define the pavement rehabilitation, the assessment of its structural capacity is required, which is obtained based on several parameters, such as deflection, which allows determining the stiffness modulus of pavement layers. The measurement of pavement deflections can be carried out by several methods, some more modern and efficient than others. This dissertation focused on the study and comparison of the methods used in assessing the structural capacity of road pavements. Thus, deflections of different pavements were measured with four different testing devices. During the measurements, the same test procedures are used for each one of the methods studied. The deflection values obtained in each pavement are statistically analyzed and compared, thereby obtaining expressions that represent the relationship between the deflections measured among the several methods. The piece of equipment with the greatest interest to be studied is the Light Falling Weight Deflectometer (LFWD), whereby an additional comparison with the conventional Falling Weight Deflectometer was made, elsewhere, in order to ascertain more precisely the relationships between the deflections measured with both devices, while comparing them to the values presented in the literature.

Dissertação de Mestrado Integrado em Engenharia Civil<br>Com um crescimento de quase 700% no parque automóvel total em Portugal desde 1974 até 2010 (fonte: ACAP), a rede rodoviária tem obrigatoriamente de se adaptar e desenvolver. Com este progresso vem a adoção de novas soluções como a criação de novas estradas e a conservação/reabilitação da rede. O estudo destas soluções de pavimentos rodoviários baseia-se no conhecimento da capacidade de carga da sua fundação. No entanto, nem sempre existe a possibilidade de realizar uma caraterização in situ desta capacidade de carga, obter o seu módulo de deformabilidade e consequentemente os módulos de deformabilidade das camadas sobrejacentes. Ainda assim, nos casos em que existe essa possibilidade, podem ser usados métodos mais precisos, mas exaustivos e morosos ou métodos mais rápidos e simples, mas cujos resultados estão ainda por clarificar, como é o caso do defletómetro de impacto ligeiro (Light Falling Weight Deflectometer, LFWD). Esta dissertação concentra-se no estudo e comparação de métodos de avaliação da capacidade de carga de solos de fundação de pavimentos rodoviários. Faz-se uma comparação entre o ensaio de carga com placa, o defletómetro de impacto ligeiro, o ensaio de CBR in situ (California Bearing Ratio) e CBR dinâmico (um ensaio ainda pouco conhecido e desenvolvido, mas com algum interesse devido à sua rápida aplicabilidade). Na impossibilidade de dizer qual o melhor método para avaliação da capacidade de carga de um solo, é possível obter o módulo de deformabilidade através da comparação de ensaios. No entanto, fica confirmado que o LFWD é, de facto, o ensaio mais rápido, simples e prático, sendo também aquele que apresenta os resultados mais conservativos.<br>With a growth of almost 700% in the total car fleet in Portugal from 1974 to 2010 (source: ACAP), the road network must adapt and develop. With this progress comes the adoption of new solutions such as the creation of new roads and conservation / rehabilitation of the network. The study of these solutions of road pavements is based on the knowledge of the load capacity of its foundation. However, it is not always possible to carry out an in situ characterization of this load capacity, to obtain its resilient modulus and consequently the resilient modulus of the layers above. Nevertheless, when this possibility exists, more precise but exhaustive and time-consuming methods may be used, or faster and simpler methods, but whose results are still to be determined, as is the case of the Light Falling Weight Deflectometer (LFWD). This dissertation is based on the study and comparison of methods for evaluating the load capacity of road pavement subgrade soils. A comparison between the plate load test, the Light Falling Weight Deflectometer, the CBR test in situ (California Bearing Ratio) and dynamic CBR (which is not yet well known and developed, but interesting due to its quick applicability). Although it was not possible to determine the best method for evaluating the load capacity of a soil, it is possible to obtain the resilient modulus by comparing the tests. However, it is confirmed that LFWD is, in fact, the fastest, simplest and most practical test, and it is also the one with the most conservative results.