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The presence of weak subgrades is one of the greatest challenges in constructing road pavements. Conventionally, techniques such as refiling with suitable material and soil stabilisation are considered to improve subgrade condition, ignoring the additional project cost. However, geogrids have gained popularity as economical, expedite and sustainable subgrade improvement techniques over recent times. Although many studies have been conducted to assess the suitability of biaxial geogrids, limited studies have been performed to check the suitability of composite geogrids for subgrade improvement, despite assuming that composite geogrids extend additional benefits. In this study, two model tests: one unreinforced and one composite geogrid reinforced, were constructed in a steel box with length, width, and height of 1 m, 1 m and 1.2 m, respectively. The subgrade was prepared to a thickness of 500 mm, achieving CBR 2.5% bearing capacity. A granular layer of 200 mm was constructed on top of the subgrade achieving 100% degree of compaction from maximum dry density. In the reinforced section, composite geogrid was placed at the base subgrade interface. Both model sections were subjected to a monotonic load at a rate of 1 mm/min, applied on the top surface of the granular layer through a circular plate of 200 mm diameter, until the occurrence of ultimate failure. Results demonstrate that reinforcing the weak subgrade by a composite geogrid has increased the ultimate bearing capacity by 53%. In addition, the overall section modulus of the composite geogrid reinforced section is higher than the modulus of the unreinforced section.

Diplomová práce se zabývá návrhem a statickým posouzením dvou variantních řešení armovaného zemního svahu na silnici I/35 v místě stávající mimoúrovňové křižovatky silnic I/35 a I/65. V diplomové práci je řešena otázka legislativních a normových požadavků v návaznosti na projektování armovaných svahů, dále je součástí práce teoretické rozdělení opěrných systémů. Praktická část se zabývá charakteristikou zájmového území a výpočtem navržených variant. Varianty následně posuzuje, porovnává a zhodnocuje z hlediska technického, ekonomického a časového., This diploma thesis deals with the design and structural assessment of two variants of structural design solution of a mechanically stabilized earth wall on the road I/35 in place of existing grade-separated junction of roads I/35 and I/65. The diploma thesis deals with the issue of legislative and norm requirements following the design of the armoured slopes, further part of the thesis is the theoretical distribution of support systems. The practical part deals with the characteristics of the territory of interest and the calculation of the proposed variants. It then assesses, compares and evaluates the variants in technical, economic and temporal terms., Dopravní fakulta Jana Pernera, Uchazeč prezentoval komisi hlavní výsledky a závěry své diplomové práce. Po prezentaci diplomové práce zodpověděl dotazy vedoucího a připomínky oponenta diplomové práce (uvedeny v posudcích práce). V diskusi o diplomové práci podrobně zodpověděl všechny dotazy členů komise., Dokončená práce s úspěšnou obhajobou

Although tire-derived aggregate (TDA) has been used as an alternative backfill in geotechnical engineering applications, the interaction between TDA having large particle sizes (e.g. TDA with a maximum particle dimension of 300 mm) and reinforcing geosynthetics has not been studied. This paper presents results from pullout tests on uniaxial and biaxial geogrids embedded in Type B TDA using a new large-scale pullout device having internal areal dimensions that can accommodate TDA layers with a height up to 1470 mm. Normal stresses ranging from 10 to 60 kPa were applied to TDA layers using dead weights atop a rigid plate and the pullout force was applied via hydraulic actuators operated in displacement control to a bolted-epoxy sandwich-type grip mounted on slide bearings that permit pullout displacements of up to 810 mm. The maximum pullout force increased with normal stress, with a displacement at maximum pullout force ranging from 100 to 350 mm. Internal displacements measured using tell-tales indicate gradual mobilization with pullout force, and the TDA layers all contracted during geogrid pullout. Uniaxial and biaxial geogrids with square-shaped apertures showed higher pullout capacity than uniaxial geogrids with rectangular-shaped apertures, but they experienced combined tensile-pullout failure at higher normal stresses.

Geogrids are the geosynthetics of choice for soil reinforcement applications. To evaluate the efficiency of geogrid reinforcement, several methods are used including field tests, laboratory tests and numerical modeling. Field studies consume long period of time and conducting these investigations may become highly expensive because of the need for real-size structures. Laboratory studies present also significant difficulties: large-size testing machines are required to accommodate realistic geogrid designs. The discrete element method (DEM) may be used as a complementary tool to extend physical testing databases at lower cost. Discrete element models do not require complex constitutive formulations and may be fed with particle scale data (size, strength, shape) thus reducing the number offree calibration parameters. Discrete element models also are well suited to problems in which large displacements are present, such as geogrid pullout. This paper reviews the different approaches followed to model soil-geogrid interaction in DEM and presents preliminary results from pull-out conditions., Peer Reviewed, Postprint (author's final draft)

Railway tracks are conventionally built on compacted ballast and structural fill layers placed above the natural (subgrade) foundation. However, during train operations, track deteriorations occur progressively due to ballast degradation. The associated track deformation is usually accompanied by a reduction in both load bearing capacity and drainage, apart from imposing frequent track maintenance. Suitable ground improvement techniques involving plastic inclusions (e.g., geogrids) and energy absorbing materials (e.g., rubber products) to enhance the stability and longevity of tracks have become increasingly popular. This paper presents the outcomes from innovative research and development measures into the use of plastic and rubber elements in rail tracks undertaken at the University of Wollongong, Australia, over the past twenty years. The results obtained from laboratory tests, mathematical modelling and numerical modelling reveal that track performance can be improved significantly by using geogrid and energy absorbing rubber products (e.g., rubber crumbs, waste tire-cell and rubber mats). Test results show that the addition of rubber materials can efficiently improve the energy absorption of the structural layer and also reduce ballast breakage. Furthermore, by incorporating the work input parameters, the energy absorbing property of the newly developed synthetic capping layer is captured by correct modelling of dilatancy. In addition, the laboratory behavior of tire cells and geogrids has been validated by numerical modelling (i.e., Finite Element Modelling-FEM, Discrete Element-DEM), and a coupled DEM-FEM modelling approach is also introduced to simulate ballast deformation.

[EN] This Final Degree Project involves the development of the search and application of a technical solution to stabilize a section of the Camino de la Estación street in Alcalá de Ebro (Zaragoza), where since the last 10 years, a series of subsidences and collapse sinkholes are taking place around the protection speck of the river Ebro from time to time. This study includes the geological and geotechnical analysis of the area as well as a series of possible solutions for facing this pathology. The best solution is identified and selected to be developed. The adopted solution consists of 28 cement mortar columns arranged staggeringly and cover by 3 geogrids of biaxial resistance inserted with layers of graded aggregates. The geotechnical design and calculation is carried out using finite element software Plaxis 8.5. This solution is designed to improve the characteristics of the ground, to distribute the superficial loads, to homogenize the subsidence and to transmit the efforts to more competent soil layers. A structural calculation of the solution is also performed and it is verified that the action improves the behavior of the soil and fulfills the objectives. In addition, a constructive process of the works is shown, following a sequence of basic tasks with his work units, and an economic estimation of the material execution of the proposed solution., [CA] El Treball Final de Grau presentat engloba el desenvolupament de la recerca i aplicació d¿una solució tècnica per estabilitzar un tram del carrer Camino de la Estación de la població d¿Alcalá de Ebro (Zaragoza), en què es produeixen periòdicament subsidències i dolines de col·lapse entorn de la mota de protecció del riu Ebro des dels últims 10 anys. En aquest estudi s¿inclou l¿anàlisi geològic ¿ geotècnic de l¿entorn per, posteriorment, plantejar una sèrie de possibles solucions per a aquesta patologia i dur a terme l¿elecció justificada d¿una d¿elles. La solució adoptada consisteix en 28 columnes de morter disposades a portell i coronades per 3 geomalles de resistència biaxial intercalades amb capes de saorres seleccionades. El disseny i càlcul geotècnic s¿ha dut a terme empleant el software d¿elements finits Plaxis a la seua versió 8.5. Aquesta solució s'ha dissenyat per millorar les característiques del terreny, repartir les càrregues superficials, homogeneïtzar les subsidències i transmetre els esforços a estrats profunds més competents. S'ha realitzat el càlcul estructural de la solució i es comprova que l'actuació millora el comportament del terreny i compleix amb els objectius plantejats. Addicionalment, s'ha plantejat un procés constructiu de l'obra seguint una seqüència de tasques bàsiques amb les seues unitats d'obra, i una estimació econòmica de l'execució material de la solució proposada., [ES] El Trabajo Final de Grado presentado abarca el desarrollo de la búsqueda y aplicación de una solución técnica para estabilizar un tramo de la calle Camino de la Estación de la población de Alcalá de Ebro (Zaragoza), en la que se producen periódicamente subsidencias y dolinas de colapso entorno a la mota de protección del río Ebro desde los últimos 10 años. En este estudio se incluye el análisis geológico ¿ geotécnico del entorno para, posteriormente, plantear una serie de posibles soluciones para esta patología y llevar a cabo la elección justificada de una de ellas. La solución adoptada consiste en 28 columnas de mortero dispuestas a tresbolillo y coronadas por 3 geomallas de resistencia biaxial intercaladas con tongadas de zahorras seleccionadas. El diseño y cálculo geotécnico se ha llevado a cabo usando el software de elementos finitos Plaxis en su versión 8.5. Esta solución se ha diseñado para mejorar las características del terreno, repartir las cargas superficiales, homogeneizar las subsidencias y transmitir los esfuerzos a estratos profundos más competentes. Se ha realizado el cálculo estructural de la solución y se comprueba que la actuación mejora el comportamiento del terreno y cumple con los objetivos planteados. Adicionalmente, se ha planteado un proceso constructivo de la obra siguiendo una secuencia de tareas básicas con sus unidades de obra, y una estimación económica de la ejecución material de la solución propuesta.

[EN] This Final Degree Project involves the development of the search and application of a technical solution to stabilize a section of the Camino de la Estación street in Alcalá de Ebro (Zaragoza), where since the last 10 years, a series of subsidences and collapse sinkholes are taking place around the protection speck of the river Ebro from time to time. This study includes the geological and geotechnical analysis of the area as well as a series of possible solutions for facing this pathology. The best solution is identified and selected to be developed. The adopted solution consists of 28 cement mortar columns arranged staggeringly and cover by 3 geogrids of biaxial resistance inserted with layers of graded aggregates. The geotechnical design and calculation is carried out using finite element software Plaxis 8.5. This solution is designed to improve the characteristics of the ground, to distribute the superficial loads, to homogenize the subsidence and to transmit the efforts to more competent soil layers. A structural calculation of the solution is also performed and it is verified that the action improves the behavior of the soil and fulfills the objectives. In addition, a constructive process of the works is shown, following a sequence of basic tasks with his work units, and an economic estimation of the material execution of the proposed solution., [CA] El Treball Final de Grau presentat engloba el desenvolupament de la recerca i aplicació d¿una solució tècnica per estabilitzar un tram del carrer Camino de la Estación de la població d¿Alcalá de Ebro (Zaragoza), en què es produeixen periòdicament subsidències i dolines de col·lapse entorn de la mota de protecció del riu Ebro des dels últims 10 anys. En aquest estudi s¿inclou l¿anàlisi geològic ¿ geotècnic de l¿entorn per, posteriorment, plantejar una sèrie de possibles solucions per a aquesta patologia i dur a terme l¿elecció justificada d¿una d¿elles. La solució adoptada consisteix en 28 columnes de morter disposades a portell i coronades per 3 geomalles de resistència biaxial intercalades amb capes de saorres seleccionades. El disseny i càlcul geotècnic s¿ha dut a terme empleant el software d¿elements finits Plaxis a la seua versió 8.5. Aquesta solució s'ha dissenyat per millorar les característiques del terreny, repartir les càrregues superficials, homogeneïtzar les subsidències i transmetre els esforços a estrats profunds més competents. S'ha realitzat el càlcul estructural de la solució i es comprova que l'actuació millora el comportament del terreny i compleix amb els objectius plantejats. Addicionalment, s'ha plantejat un procés constructiu de l'obra seguint una seqüència de tasques bàsiques amb les seues unitats d'obra, i una estimació econòmica de l'execució material de la solució proposada., [ES] El Trabajo Final de Grado presentado abarca el desarrollo de la búsqueda y aplicación de una solución técnica para estabilizar un tramo de la calle Camino de la Estación de la población de Alcalá de Ebro (Zaragoza), en la que se producen periódicamente subsidencias y dolinas de colapso entorno a la mota de protección del río Ebro desde los últimos 10 años. En este estudio se incluye el análisis geológico ¿ geotécnico del entorno para, posteriormente, plantear una serie de posibles soluciones para esta patología y llevar a cabo la elección justificada de una de ellas. La solución adoptada consiste en 28 columnas de mortero dispuestas a tresbolillo y coronadas por 3 geomallas de resistencia biaxial intercaladas con tongadas de zahorras seleccionadas. El diseño y cálculo geotécnico se ha llevado a cabo usando el software de elementos finitos Plaxis en su versión 8.5. Esta solución se ha diseñado para mejorar las características del terreno, repartir las cargas superficiales, homogeneizar las subsidencias y transmitir los esfuerzos a estratos profundos más competentes. Se ha realizado el cálculo estructural de la solución y se comprueba que la actuación mejora el comportamiento del terreno y cumple con los objetivos planteados. Adicionalmente, se ha planteado un proceso constructivo de la obra siguiendo una secuencia de tareas básicas con sus unidades de obra, y una estimación económica de la ejecución material de la solución propuesta.

[EN] This Final Degree Project involves the development of the search and application of a technical solution to stabilize a section of the Camino de la Estación street in Alcalá de Ebro (Zaragoza), where since the last 10 years, a series of subsidences and collapse sinkholes are taking place around the protection speck of the river Ebro from time to time. This study includes the geological and geotechnical analysis of the area as well as a series of possible solutions for facing this pathology. The best solution is identified and selected to be developed. The adopted solution consists of 28 cement mortar columns arranged staggeringly and cover by 3 geogrids of biaxial resistance inserted with layers of graded aggregates. The geotechnical design and calculation is carried out using finite element software Plaxis 8.5. This solution is designed to improve the characteristics of the ground, to distribute the superficial loads, to homogenize the subsidence and to transmit the efforts to more competent soil layers. A structural calculation of the solution is also performed and it is verified that the action improves the behavior of the soil and fulfills the objectives. In addition, a constructive process of the works is shown, following a sequence of basic tasks with his work units, and an economic estimation of the material execution of the proposed solution., [CA] El Treball Final de Grau presentat engloba el desenvolupament de la recerca i aplicació d¿una solució tècnica per estabilitzar un tram del carrer Camino de la Estación de la població d¿Alcalá de Ebro (Zaragoza), en què es produeixen periòdicament subsidències i dolines de col·lapse entorn de la mota de protecció del riu Ebro des dels últims 10 anys. En aquest estudi s¿inclou l¿anàlisi geològic ¿ geotècnic de l¿entorn per, posteriorment, plantejar una sèrie de possibles solucions per a aquesta patologia i dur a terme l¿elecció justificada d¿una d¿elles. La solució adoptada consisteix en 28 columnes de morter disposades a portell i coronades per 3 geomalles de resistència biaxial intercalades amb capes de saorres seleccionades. El disseny i càlcul geotècnic s¿ha dut a terme empleant el software d¿elements finits Plaxis a la seua versió 8.5. Aquesta solució s'ha dissenyat per millorar les característiques del terreny, repartir les càrregues superficials, homogeneïtzar les subsidències i transmetre els esforços a estrats profunds més competents. S'ha realitzat el càlcul estructural de la solució i es comprova que l'actuació millora el comportament del terreny i compleix amb els objectius plantejats. Addicionalment, s'ha plantejat un procés constructiu de l'obra seguint una seqüència de tasques bàsiques amb les seues unitats d'obra, i una estimació econòmica de l'execució material de la solució proposada., [ES] El Trabajo Final de Grado presentado abarca el desarrollo de la búsqueda y aplicación de una solución técnica para estabilizar un tramo de la calle Camino de la Estación de la población de Alcalá de Ebro (Zaragoza), en la que se producen periódicamente subsidencias y dolinas de colapso entorno a la mota de protección del río Ebro desde los últimos 10 años. En este estudio se incluye el análisis geológico ¿ geotécnico del entorno para, posteriormente, plantear una serie de posibles soluciones para esta patología y llevar a cabo la elección justificada de una de ellas. La solución adoptada consiste en 28 columnas de mortero dispuestas a tresbolillo y coronadas por 3 geomallas de resistencia biaxial intercaladas con tongadas de zahorras seleccionadas. El diseño y cálculo geotécnico se ha llevado a cabo usando el software de elementos finitos Plaxis en su versión 8.5. Esta solución se ha diseñado para mejorar las características del terreno, repartir las cargas superficiales, homogeneizar las subsidencias y transmitir los esfuerzos a estratos profundos más competentes. Se ha realizado el cálculo estructural de la solución y se comprueba que la actuación mejora el comportamiento del terreno y cumple con los objetivos planteados. Adicionalmente, se ha planteado un proceso constructivo de la obra siguiendo una secuencia de tareas básicas con sus unidades de obra, y una estimación económica de la ejecución material de la solución propuesta.

[EN] This Final Degree Project involves the development of the search and application of a technical solution to stabilize a section of the Camino de la Estación street in Alcalá de Ebro (Zaragoza), where since the last 10 years, a series of subsidences and collapse sinkholes are taking place around the protection speck of the river Ebro from time to time. This study includes the geological and geotechnical analysis of the area as well as a series of possible solutions for facing this pathology. The best solution is identified and selected to be developed. The adopted solution consists of 28 cement mortar columns arranged staggeringly and cover by 3 geogrids of biaxial resistance inserted with layers of graded aggregates. The geotechnical design and calculation is carried out using finite element software Plaxis 8.5. This solution is designed to improve the characteristics of the ground, to distribute the superficial loads, to homogenize the subsidence and to transmit the efforts to more competent soil layers. A structural calculation of the solution is also performed and it is verified that the action improves the behavior of the soil and fulfills the objectives. In addition, a constructive process of the works is shown, following a sequence of basic tasks with his work units, and an economic estimation of the material execution of the proposed solution., [CA] El Treball Final de Grau presentat engloba el desenvolupament de la recerca i aplicació d¿una solució tècnica per estabilitzar un tram del carrer Camino de la Estación de la població d¿Alcalá de Ebro (Zaragoza), en què es produeixen periòdicament subsidències i dolines de col·lapse entorn de la mota de protecció del riu Ebro des dels últims 10 anys. En aquest estudi s¿inclou l¿anàlisi geològic ¿ geotècnic de l¿entorn per, posteriorment, plantejar una sèrie de possibles solucions per a aquesta patologia i dur a terme l¿elecció justificada d¿una d¿elles. La solució adoptada consisteix en 28 columnes de morter disposades a portell i coronades per 3 geomalles de resistència biaxial intercalades amb capes de saorres seleccionades. El disseny i càlcul geotècnic s¿ha dut a terme empleant el software d¿elements finits Plaxis a la seua versió 8.5. Aquesta solució s'ha dissenyat per millorar les característiques del terreny, repartir les càrregues superficials, homogeneïtzar les subsidències i transmetre els esforços a estrats profunds més competents. S'ha realitzat el càlcul estructural de la solució i es comprova que l'actuació millora el comportament del terreny i compleix amb els objectius plantejats. Addicionalment, s'ha plantejat un procés constructiu de l'obra seguint una seqüència de tasques bàsiques amb les seues unitats d'obra, i una estimació econòmica de l'execució material de la solució proposada., [ES] El Trabajo Final de Grado presentado abarca el desarrollo de la búsqueda y aplicación de una solución técnica para estabilizar un tramo de la calle Camino de la Estación de la población de Alcalá de Ebro (Zaragoza), en la que se producen periódicamente subsidencias y dolinas de colapso entorno a la mota de protección del río Ebro desde los últimos 10 años. En este estudio se incluye el análisis geológico ¿ geotécnico del entorno para, posteriormente, plantear una serie de posibles soluciones para esta patología y llevar a cabo la elección justificada de una de ellas. La solución adoptada consiste en 28 columnas de mortero dispuestas a tresbolillo y coronadas por 3 geomallas de resistencia biaxial intercaladas con tongadas de zahorras seleccionadas. El diseño y cálculo geotécnico se ha llevado a cabo usando el software de elementos finitos Plaxis en su versión 8.5. Esta solución se ha diseñado para mejorar las características del terreno, repartir las cargas superficiales, homogeneizar las subsidencias y transmitir los esfuerzos a estratos profundos más competentes. Se ha realizado el cálculo estructural de la solución y se comprueba que la actuación mejora el comportamiento del terreno y cumple con los objetivos planteados. Adicionalmente, se ha planteado un proceso constructivo de la obra siguiendo una secuencia de tareas básicas con sus unidades de obra, y una estimación económica de la ejecución material de la solución propuesta.

рассматриваются причины и возможные последствия ошибок при устройстве современных материалов, которые влияют на качество и стоимость строительства автомобильных дорог, discusses the causes and possible consequences of errors in the device of modern materials that affect the quality and cost of road construction

This paper presents an analytical approach to determine the ultimate load-bearing capacity of a footing subjected to a vertical load and resting on the top of a fly ash slope without or with single or multi-layers geogrid reinforcement. The load-bearing capacity values obtained by using the proposed analytical approach were compared with those obtained from experimental and numerical approaches reported recently in the literature. After validation of the analytical values of the load bearing capacity, an empirical formula based on a regression analysis was developed between the bearing capacity ratio and geogrid index (α), which physically signifies the mobilized strength of geogrid reinforcement under a given footing load and is a function of the number of reinforcement layers (N) and the embedment ratio (z/B).

Geogrids have been used for a long time in pavement rehabilitation projects in order to slow down the reflection of cracks from the existing pavement. This paper presents the results of an experiment performed in Belgrade in the boulevard of Prince Alexander Karađorđević, where trial section with geogrids was contructed in driving lane as part of during pavement rehabilitation project in 2003. Pavement condition surveys were performed on three occasions, in 2005, 2008, and 2013. Based on the analysis of results, it can be concluded that: The extent of cracking in the driving lane on the left carriageway (with geogrids) is much smaller than the extent of cracking in the driving lane on the right carriageway (without geogrids). The cracking on the left carriageway (with geogrids) appeared later and had slower progression compared to the right carriageway, especially in the first five years after rehabilitation The trend of cracking development accelerates with time. The use of geogrid at the bus stops did not help to substantially reduce rutting. The main reason is the inadequate position of the geogrid that is placed below the bituminous base course, instead of being placed between bitumenious base and surface courses. ., Geomreže se već duže vreme primenjuju u projektima rehabilitacije kolovoznih konstrukcija sa ciljem da se uspori reflektovanje pukotina iz postojeće kolovozne konstrukcije. U radu su prikazani rezultati praćenja stanja oštećenosti opitne deonice na Bulevaru kneza Aleksandra Karađorđevića u Beogradu na čijem delu su tokom 2003. godine prilikom rehabilitacije kolovozne konstrukcije ugrađene geomreže u voznoj traci. Snimanje oštećenosti kolovozne konstrukcije obavljeno je u tri navrata, 2005., 2008. i 2013. godine. U okviru analize rezultata može se zaključiti: da je obim pukotina u voznoj traci na levom kolovozu (sa mrežama) znatno manji od obima pukotina u voznoj traci na desnom kolovozu (bez mreža); da su se na traci sa mrežama pukotine kasnije reflektovale i imale sporiji prirast u odnosu na trake bez mreža, posebno u prvih 5 godina posle rehabilitacije; da se trend razvoja pukotina ubrzava sa vremenom. Primena mreže na autobuskim stajalištima nije pomogla da se značajnije smanji dubina kolotraga. Osnovni razlog je neadekvatna pozicija mreže koja je postavljena ispod bitumeniziranog nosećeg sloja, umesto da bude postavljena između bitumeniziranog nosećeg i habajućeg sloja. .

Geogrids have been used for a long time in pavement rehabilitation projects in order to slow down the reflection of cracks from the existing pavement. This paper presents the results of an experiment performed in Belgrade in the boulevard of Prince Alexander Karađorđević, where trial section with geogrids was contructed in driving lane as part of during pavement rehabilitation project in 2003. Pavement condition surveys were performed on three occasions, in 2005, 2008, and 2013. Based on the analysis of results, it can be concluded that: The extent of cracking in the driving lane on the left carriageway (with geogrids) is much smaller than the extent of cracking in the driving lane on the right carriageway (without geogrids). The cracking on the left carriageway (with geogrids) appeared later and had slower progression compared to the right carriageway, especially in the first five years after rehabilitation The trend of cracking development accelerates with time. The use of geogrid at the bus stops did not help to substantially reduce rutting. The main reason is the inadequate position of the geogrid that is placed below the bituminous base course, instead of being placed between bitumenious base and surface courses. ., Geomreže se već duže vreme primenjuju u projektima rehabilitacije kolovoznih konstrukcija sa ciljem da se uspori reflektovanje pukotina iz postojeće kolovozne konstrukcije. U radu su prikazani rezultati praćenja stanja oštećenosti opitne deonice na Bulevaru kneza Aleksandra Karađorđevića u Beogradu na čijem delu su tokom 2003. godine prilikom rehabilitacije kolovozne konstrukcije ugrađene geomreže u voznoj traci. Snimanje oštećenosti kolovozne konstrukcije obavljeno je u tri navrata, 2005., 2008. i 2013. godine. U okviru analize rezultata može se zaključiti: da je obim pukotina u voznoj traci na levom kolovozu (sa mrežama) znatno manji od obima pukotina u voznoj traci na desnom kolovozu (bez mreža); da su se na traci sa mrežama pukotine kasnije reflektovale i imale sporiji prirast u odnosu na trake bez mreža, posebno u prvih 5 godina posle rehabilitacije; da se trend razvoja pukotina ubrzava sa vremenom. Primena mreže na autobuskim stajalištima nije pomogla da se značajnije smanji dubina kolotraga. Osnovni razlog je neadekvatna pozicija mreže koja je postavljena ispod bitumeniziranog nosećeg sloja, umesto da bude postavljena između bitumeniziranog nosećeg i habajućeg sloja. .

[Resumen:] Este artículo realiza un acercamiento general a la utilización actual de los geosintéticos en el diseño y construcción de carreteras. Una vez hecho ese acercamiento general se presentan planteamientos para la aplicación de este tipo de materiales en el diseño del firme de las carreteras en nuestro país. Finalmente se presentan las conclusiones y futuros desarrollos para avanzar en la utilización de esta tecnología en las capas de firme a nivel nacional., [Abstract:] This paper takes a general approach of geosynthetics in the design and roads construction current use. Afterward proposals for the implementation of these materials in the design of road surfaces in our country are presented. Finally, conclusions and future developments to advance the use of this technology in pavement layers nationwide are presented.

This paper describes a case history of a geogrid-reinforced and pile-supported (GRPS) highway embankment with a low area improvement ratio of 8.7\%. Field monitored data from contact pressures acting on the pile and soil surfaces, pore-water pressures, settlements and lateral displacements are reported and discussed. The case history is backanalyzed by carrying out three-dimensional (3D) fully coupled finite-element analysis. The measured and computed results are compared and discussed. Based on the field observations of contact stresses and pore-water pressures and the numerical simulations of the embankment construction, it is clear that there was a significant load transfer from the soil to the piles due to soil arching. The measured contact pressure acting on the pile was about 14 times higher than that acting on the soil located between the piles. This transfer greatly reduced excess positive pore water pressures induced in the soft silty clay. The measured excess pore water pressure ratio (B) over bar (max) in the soft silty clay was only about 0.3. For embankment higher than 2.5 m, predictions of stress reduction ratio based on two common existing design methods are consistent with the measured values and the 3D numerical simulations. During the construction of the piled embankment, the measured lateral displacement-settlement ratio was only about 0.2. This suggests that the use of GRPS system can reduce lateral displacements and enhance the stability of an embankment significantly.

This paper describes a case history of a geogrid-reinforced and pile-supported (GRPS) highway embankment with a low area improvement ratio of 8.7\%. Field monitored data from contact pressures acting on the pile and soil surfaces, pore-water pressures, settlements and lateral displacements are reported and discussed. The case history is backanalyzed by carrying out three-dimensional (3D) fully coupled finite-element analysis. The measured and computed results are compared and discussed. Based on the field observations of contact stresses and pore-water pressures and the numerical simulations of the embankment construction, it is clear that there was a significant load transfer from the soil to the piles due to soil arching. The measured contact pressure acting on the pile was about 14 times higher than that acting on the soil located between the piles. This transfer greatly reduced excess positive pore water pressures induced in the soft silty clay. The measured excess pore water pressure ratio (B) over bar (max) in the soft silty clay was only about 0.3. For embankment higher than 2.5 m, predictions of stress reduction ratio based on two common existing design methods are consistent with the measured values and the 3D numerical simulations. During the construction of the piled embankment, the measured lateral displacement-settlement ratio was only about 0.2. This suggests that the use of GRPS system can reduce lateral displacements and enhance the stability of an embankment significantly.

This paper describes a case history of a geogrid-reinforced and pile-supported (GRPS) highway embankment with a low area improvement ratio of 8.7\%. Field monitored data from contact pressures acting on the pile and soil surfaces, pore-water pressures, settlements and lateral displacements are reported and discussed. The case history is backanalyzed by carrying out three-dimensional (3D) fully coupled finite-element analysis. The measured and computed results are compared and discussed. Based on the field observations of contact stresses and pore-water pressures and the numerical simulations of the embankment construction, it is clear that there was a significant load transfer from the soil to the piles due to soil arching. The measured contact pressure acting on the pile was about 14 times higher than that acting on the soil located between the piles. This transfer greatly reduced excess positive pore water pressures induced in the soft silty clay. The measured excess pore water pressure ratio (B) over bar (max) in the soft silty clay was only about 0.3. For embankment higher than 2.5 m, predictions of stress reduction ratio based on two common existing design methods are consistent with the measured values and the 3D numerical simulations. During the construction of the piled embankment, the measured lateral displacement-settlement ratio was only about 0.2. This suggests that the use of GRPS system can reduce lateral displacements and enhance the stability of an embankment significantly.

Evidence from experimental and field applications suggest that the presence of geogrid in highway base course increases the ability of a granular material to compact. The addition of a geogrid into an aggregate base layer may decrease the lateral spreading of the base material as compaction effort is applied, leading to a greater potential for the base course to compact vertically. The hypothesis being examined is that given an equal amount of compactive effort, geogrid reinforced base course material can achieve a greater density than non-reinforced base course. This hypothesis was evaluated by the construction of test sections with and without geogrid, compaction of these test sections using small field-scale equipment, and measurement of density and void ratio by various means. The effects of varying lift thicknesses and compactive efforts were also evaluated. Changes in density were recorded with a nuclear densometer. A Dynamic Cone Penetrometer (DCP) was also used to indicate relative density of the base course. The third procedure for evaluating density and void ratio versus depth was accomplished via computer aided tomography (CAT). CAT combines ordinary X-ray technology with sophisticated computer signal processing and delivers digital images capable of being analyzed with selected software. The software was then used to calculate a series of void ratios for soil samples taken from the reinforced and non-reinforced sections. An average void ratio for each section was then computed and the results for each reinforced and non-reinforced section compared. Based upon review of density results and DCP measurements, there does not seem to be a clear indication that geogrid reinforced base course material achieves a greater density than non-reinforced material given the same amount of compactive effort. The void ratios obtained via CAT scan analysis do show a better distinction between the two configurations.

Summary: An experimental and analytical investigation is presented for two types of geogrids: HDPE (High Density Polyethylene) and PET (Polyester). Sand and limerock were used for the backfill material, which meet the FDOT (Florida Department of Transportation) Material Specifications, with simulation of unsaturated and saturated condition. Eight pullout test boxes were designed and constructed, each with a specially designed stainless steel clamp. The measured strain-time relations for unsaturated and saturated soils for various levels of the pullout force until the peak value (up to 10,000 hours of exposure), and varying distances from the loading end were plotted. The normal and principal stresses in the soil, and the strains along the geogrid were determined from the finite element analysis for the unsaturated soil condition for various pullout force levels. The results were analyzed and a generalized method proposed for practical design using sliding resistance factors., College of Engineering and Computer Science, Collection: FAU Electronic Theses and Dissertations Collection, Thesis (M.S.)--Florida Atlantic University, 1999.

Experimental and analytical investigations were performed to evaluate the comparative performance of pavements with and without geosynthetic stabilization. This was accomplished by the testing of a total of 18 pavement sections which could be classified into four different types: one which was constructed without geosynthetics and which served as a control, and three which were stabilized with one of two geotextiles or a geogrid. The pavement sections were constructed to model a typical secondary road in Virginia which is constructed over a silty sand subgrade material. Loading of the pavement sections was accomplished through the use of a computer-controlled pneumatic system which delivered 80 lb/in2 (552 kPa) through a rigid plate at a frequency of approximately one-half Hertz. The resulting displacement of the pavement surface was monitored by an array of linear variable displacement transducers (LVDTs). The performance of each pavement section was evaluated using the American Association of State Highway and Transportation Officials (AASHTO) flexible pavement design method. Models based on empirical and mechanistic relationships were considered. A theoretical pavement section was also analyzed to assess the influence of the stiffness of a wearing course layer. An economic study was performed to assess the potential cost benefit of geosynthetic stabilization and recommendations have been made for additional research.

The objective of this study was to investigate the response of reinforced soil systems subjected to blast loading and to assess the feasibility of using reinforced soil to provide blast resistance. To meet this objective, a testing program was developed and executed to accomplish the following: (1) to establish the properties of reinforced soil subjected to blast loading, (2) to develop numerical and physical modeling techniques which are appropriate for evaluating the response of reinforced soil systems subjected to blast loading, and (3) to establish preliminary analysis methods which can be used for the design of reinforced soil systems subjected to blast loading.

These guidelines have been condensed from the FHWA Geotextile Engineering Manual (1985) for use as an implementationdocument for project managers and highway designers. It will also be useful as a design reference guide for pavement and geotechnical specialists. The guidelines when used in conjunction with the FHWA Geotextile Engineering Manual will enable the highway engineer to properly design, select, test, specify, and construct with geotextiles and related products such as geogrids and geocomposite drainage materials. Af ter a general introductory chapter, application chapters are presented on drainage, erosion control (permanent and temporary), roadways, pavement overlays, and reinforced embankments, slopes, and retaining walls and abutments. Each chapter presents step-by-step procedures for design, selection, and installation of geotextiles for these applications. For additional information, references are provided to supplement those given in the FHWA Geotextile Engineering Manual., KWP-collection

These guidelines have been condensed from the FHWA Geotextile Engineering Manual (1985) for use as an implementationdocument for project managers and highway designers. It will also be useful as a design reference guide for pavement and geotechnical specialists. The guidelines when used in conjunction with the FHWA Geotextile Engineering Manual will enable the highway engineer to properly design, select, test, specify, and construct with geotextiles and related products such as geogrids and geocomposite drainage materials. Af ter a general introductory chapter, application chapters are presented on drainage, erosion control (permanent and temporary), roadways, pavement overlays, and reinforced embankments, slopes, and retaining walls and abutments. Each chapter presents step-by-step procedures for design, selection, and installation of geotextiles for these applications. For additional information, references are provided to supplement those given in the FHWA Geotextile Engineering Manual., KWP-collection

Geogrid has been defined as a deformed or nondeformed net-like polymetric material used with foundation, soil, rock, earth, or any other geotechnical engineering-related materials as an integral part of a human-made project, structure, or system. Geogrids are one of the geosynthetics that have seen increased use in railroad applications. In conjunction with design of railroad track at several military installations the question was raised as to the benefit of including a geogrid in the ballast to act as a reinforcement mechanism. The use of geogrids in railroad track applications was investigated to determine if the ballast thickness can be reduced using geogrids. Investigation was made of the advantages and disadvantages of using geogrids along with the possibility of reducing the ballast thickness through the use of a geogrid. All available technical literature applicable to the use of geogrids in railroad track was reviewed. A number of telephone calls and personal contacts were made with people in academia and in the geosynthetics and railroad industries who have been involved with the development, testing, and use of these materials in railroad track. A synopsis of the information that is currently available in relation to the use of geogrids in railroad track reinforcement is presented along with recommendations for the use of geogrids on low traffic density, low speed railroad tracks typical of those found on military installations.

A geotextile is defined by ASTM as: any permeable textile material used with foundation, soil, rock, earth, or any other geotechnical engineering related material, as a integral part of a man-made project, structure, or system. A geogrid is defined as: any geotextile-related material used in a similar manner to geotextiles. They are usually made of plastic, but can be metal or wood. Geotextiles and geogrids are collectively referred to as geosynthetics in this paper. Geosynthetic reinforcement of slopes is a relatively new option available to the civil engineer. Slope angles can be increased and 'poor' soil can be used to construct economical soil-geosynthetic facilities. Uncertainties exist in the complex interaction between the soil and the geosynthetic but there are numerous procedures which ignore this in the design. The design procedures available may be conservative yet still may be an economical alternative when compared to more conventional options.

Poor reproducibility among laboratories that use the ASTM D2274 test for the storage stability of distillate fuels has long been a problem. Different operators who use the same equipment obtained different average results even within a single laboratory. A questionnaire relating to the method was sent to users to elicit information about variations in practice among laboratories and to gain insight into the causes. This Center began a task to identify the critical variables in the test procedure. We tested three fuels and concluded that there is negligible effect from variations in the bath temperature of less than 0.2 C (32.4 F), in oxygen flow rate of less than 0.3 L/hr, and of time-in-bath of less than 0.25 hr. However, each of these variables (especially the temperature) has a major impact if the limits are exceeded.

Introduction of high-strength geosynthetic materials has allowed for construction on heretofore impossible sites. Saturated, fine-grained soils with in-situ unconsolidates-undrained strengths as low as 1.0 kPa (20.8 lb/sq ft) have been successfully used for embankment foundations using geotextiles or geogrids for direct ground support. When rapid consolidation of the subsoil is desirable, the procedure sometimes calls for insertion of strip (wick) drains and, for lateral flow, drainage geocomposites as well. This paper reviews and summarized a number of soft-soil stabilization projects. Drawing from these experiences, a five-part design method is presented to select and size the various goesynthetic material properties involved. Keywords: Dikes; Dredged material disposal areas or containment; Soft foundations; Slope stability analysis; Geosynthetics; Geotextile.

Singh, M., Trivedi, A., & Shukla, S. K. (2019). Strength enhancement of the subgrade soil of unpaved road with geosynthetic reinforcement layers. Transportation Geotechnics, 19, 54-60. Available here

Kazi, M., Shukla, S. K., & Habibi, D. (2015). Behaviour of an embedded footing on geotextile-reinforced sand. Proceedings of the Institution of Civil Engineers-Ground Improvement, 169(2), 120-133. Available here

The purpose of this research project was to investigate and determine the reasons for the premature deterioration of the geogrid-reinforced pavement system on the section of SR-10 between Muddy Creek and Emery, Utah. Statistical analyses and evaluations indicate that the structural design of the primary pavement system was adequate, as the stiffness measurements of the primary layers did not correlate with measured pavement distress. Even though the asphalt-concrete layer was subjected to significant deformations in the longitudinal and transverse directions, it displayed negligible cracking. Therefore, the geogrid likely provided the necessary tensile reinforcement to prevent tension cracking in the asphalt-concrete layer despite large movements within the embankment and subgrade. The characteristics of the fill and subgrade likely dominated the performance of the pavement. The structural design of the pavement system did not take into account the vulnerability of the subgrade and embankment to loading-induced and wetting-induced volume changes. Subgrade soil from cut sections was sampled and tested for collapse and swell potential. It was found to swell under low overburden pressures and collapse under medium to high overburden pressures. This soil, or similar native soil, was likely used as native embankment fill in some pavement sections. Sections with embankment fills under the negative direction of travel were vulnerable to loading-induced and wetting-induced volume changes. Additional commentary and recommendations are provided in this report for suitable embankment fill material and pavement support materials, along with effective placement of geogrid and geotextile in a pavement section for future Utah Department of Transportation (UDOT) projects.

The geogrid-reinforced pavement system on the section of State Route 10 between Muddy Creek and Emery, Utah, experienced premature deterioration. Research was needed to understand the reasons for this deterioration and to develop an improved understanding of the significant influence that native subgrade and fill materials have on the performance of pavement systems constructed on soft subgrades and how geogrid can limit damage stemming from these materials.

C2169, Lightweight Cellular Concrete (LCC) (also called foam or gas concrete) is a special construction material, which is typically composed of portland cement, water, and air voids created by a foaming agent. This material has been increasingly used as a backfill material for geotechnical applications. This report presents a series of laboratory tests conducted to evaluate the material properties of LCC including density, permeability, compressive strength, shear strength, compressibility, elastic modulus, and Poisson’s ratio with different cement to fly ash ratios and at different ages. LCC specimens used in this research project were cast in the field, and the cement to fly ash ratios used for the production of the specimens ranged from 50:50 to 100:0. Large direct shear box tests were conducted on prismatic specimens with a size of 12 inches long, 12 inches wide, and 8 inches high, while small direct shear box tests were conducted on cylindrical specimens with a size of 2.5 inches in diameter and 1 inch high. This report also presents a series of pullout tests conducted in the laboratory to investigate pullout resistance of extensible reinforcement (geogrid) and inextensible reinforcement (steel strip) embedded in LCC. Pullout displacements and pullout forces were monitored using linear variable displacement transducers (LVDT) and a load cell during the pullout process. This research project investigated the effects of age, normal stress, LCC type, cold joint, and re-pullout on pullout resistance and calculated the pullout resistance factors F* for geogrid and steel strip embedded in LCC. The laboratory material test results show that the average wet densities of LCC ranged from 30 to 36 pcf at the age of 28 days and the average dry densities ranged from 21 to 24 pcf at the same age. The permeability values of LCC ranged from 2.1×10-5 to 3.0×10-4 in./s and they increased as the cement to fly ash ratio increased. The measured cohesion values of LCC in large direct shea

This report presents a series of laboratory tests to evaluate the material properties of LCC and the pullout resistances of geogrid and steel strip in LCC specimens cast in the field. Based on the test results, the following conclusions can be drawn: The average wet densities of LCC ranged from 30 to 36 pcf at the age of 28 days and the average dry densities ranged from 21 to 24 pcf at the same age. The dry density was approximately 67% of the wet density. The density increased as the cement to fly ash ratio increased. All LCC specimens used in this study are considered ultra-low density cellular concrete. The permeability values for LCC measured using the falling head method ranged from 2.1×10-5 to 3.0×10-4 in./s, respectively. In general, the permeability decreased as the hydraulic gradient and the confining stress increased. For the small shear box tests, the cohesion values of the LCC specimens ranged from 19 to 37 psi, while their frictional angles ranged from 19 to 63 degrees. For the large shear box tests, the cohesion values of the LCC specimens ranged from 33 to 50 psi, while their frictional angles ranged from 23 to 79 degrees. The large shear box tests measured higher shear strengths than the small shear box tests.

P227-21-803, Geosynthetics have been used to reinforce aggregate base courses to increase the structural support from the base to the pavement structure. This project aims to develop a study framework to evaluate and quantify the structural benefits under Nevada conditions. To achieve this objective, a five-stage research plan was developed to support a controlled field demonstration, with input regarding design, specification, and standards. This report provides a methodology to determine the expected design life of a specific site with known climate characteristics, subgrade modulus, and traffic. Included are recommendations for the pavement design, testing layout, testing plan, construction guidelines, preliminary implementation plan, and cost estimate.

Roads in Louisiana are often built over weak subgrade soils due to the soft nature of subsurface soils and the presence of high water tables, which create many design and construction challenges. A common practice in Louisiana is to stabilize/treat the upper part of subgrade with cement or lime, depending on the subgrade soil type. This practice can help reduce the risks of excessive permanent deformations (rutting) by spreading the tire pressure into a wider area, thus reducing the vertical pressure on top of the untreated subgrade layer.

65A0556, This report presents results from shaking table tests on half-scale mechanically-stabilized earth (MSE) bridge abutments. The testing program consists of five tests where the direction of shaking is in the longitudinal direction of the bridge beam, and one test where the direction of shaking is perpendicular to the bridge beam. The longitudinal shaking tests include a baseline configuration and a parametric study of different configurations to investigate the effects of bridge surcharge stress, reinforcement spacing, reinforcement stiffness, and steel reinforcement on the seismic response of MSE bridge abutments. Experimental design of the scale model followed established similitude relationships for shaking table testing in a 1g gravitational field, including scaling for of geometry, reinforcement stiffness, backfill soil modulus, bridge surcharge stress, and characteristics of the earthquake motions. Facing displacements, bridge seat settlements, accelerations, vertical and lateral stresses, reinforcement strains, and contact forces between the bridge beam and bridge seat were measured for different instrumented sections to evaluate the three-dimensional dynamic response during a series of applied shaking motions. Results indicate that reinforcement spacing and reinforcement stiffness have the most significant effects on the facing displacements and bridge seat settlements for dynamic loading conditions.

Track deterioration has a serious influence on the safety and efficiency (speed restriction) of train operations. Many expensive, disruptive and frequent repair operations are often required to maintain the ballast characteristics due to the problem of settlement. Because of this, a geogrid solution that has proved to be a simple and economical method of reinforcing track ballast is widely used. This project presents an evaluation of the behaviour of geogrid-reinforced railway ballast. Experimental large box pull-out tests were conducted to examine the key parameters influencing the interaction between ballast and the geogrid. The experimental results demonstrated that the triaxial geogrid with triangular apertures outperforms the biaxial geogrid with square apertures and the geogrid aperture size is more influential than rib profile and junction profile. The discrete element method (DEM) has then been used to model the interaction between ballast and geogrid by simulating large box pull-out tests and comparing with experimental results. The DEM simulation results have been shown to provide good predictions of the pull-out resistance and reveal the distribution of contact forces in the geogrid-reinforced ballast system. The discrete element method has also been used to simulate cyclic loading of geogrid-reinforced ballast under confined and unconfined conditions. For the confined condition, box tests have been simulated on unreinforced samples and reinforced samples with different geogrid positions and geogrid apertures. The response of the ballast layer reinforced with geogrid under repeated loading agrees with experimental results. It was found that the optimum location of geogrid is 100 mm depth from base, and the triaxial geogrid outperforms biaxial geogrid. For the unconfined condition, cyclic loading of a trough of ballast has also been simulated, and the sample with the geogrid at 50mm from the sub-ballast layer performs best. It was also found that the used

RES # 2019-12, Accelerated pavement test (APT) is defined as the controlled application of a prototype wheel loading at the appropriate load to the full-scale pavement structure, which is used to determine the structural responses and performance of the pavement in a short period. Inverted pavement is an unconventional type of flexible pavement structure. In this pavement structure, an unbound aggregate base (UAB) with a low initial modulus is layered between two stiffer layers, an asphalt concrete layer (AC) and a cement-treated base layer (CTB). This project presents two rounds of APT tests on full-scale inverted pavements. In the first-round APT, a comparison study on the rutting performance between the conventional and inverted pavement structures was presented. In addition, the inverted pavements with different thicknesses of UAB and CTB were studied. Significant permanent deflections were observed in all three pavement lanes after 100k passes of APT. Based on the measured deformation, the inverted pavement structure outperformed the conventional pavement in terms of the final surface deformation. And the inverted pavement with a thicker CTB layer had a better performance than the inverted pavement with a thicker UAB layer. Based on the overall pavement conditions, the inverted pavement can be regarded as an alternative to the conventional flexible pavement, and asphalt mixture layer thickness can be reduced during construction. In the second round of APT, the effect of geogrids in the inverted pavement was investigated. The polypropylene geogrids were installed in the full-scale inverted pavements and different locations of geogrids were discussed as well. After 150k passes of APT, the rutting performance was compared and studied. The results show that the geogrids could improve the rutting resistance of the inverted pavement, but the effect of geogrids depended on the location in the UAB layer. In this study, the geogrids placed at the upper 1/3 upper layer of UAB displayed

Track deterioration has a serious influence on the safety and efficiency (speed restriction) of train operations. Many expensive, disruptive and frequent repair operations are often required to maintain the ballast characteristics due to the problem of settlement. Because of this, a geogrid solution that has proved to be a simple and economical method of reinforcing track ballast is widely used. This project presents an evaluation of the behaviour of geogrid-reinforced railway ballast. Experimental large box pull-out tests were conducted to examine the key parameters influencing the interaction between ballast and the geogrid. The experimental results demonstrated that the triaxial geogrid with triangular apertures outperforms the biaxial geogrid with square apertures and the geogrid aperture size is more influential than rib profile and junction profile. The discrete element method (DEM) has then been used to model the interaction between ballast and geogrid by simulating large box pull-out tests and comparing with experimental results. The DEM simulation results have been shown to provide good predictions of the pull-out resistance and reveal the distribution of contact forces in the geogrid-reinforced ballast system. The discrete element method has also been used to simulate cyclic loading of geogrid-reinforced ballast under confined and unconfined conditions. For the confined condition, box tests have been simulated on unreinforced samples and reinforced samples with different geogrid positions and geogrid apertures. The response of the ballast layer reinforced with geogrid under repeated loading agrees with experimental results. It was found that the optimum location of geogrid is 100 mm depth from base, and the triaxial geogrid outperforms biaxial geogrid. For the unconfined condition, cyclic loading of a trough of ballast has also been simulated, and the sample with the geogrid at 50mm from the sub-ballast layer performs best. It was also found that the used

Experimental Features Project No. OR 89-01, The KeyStone/Tensar Geogrid retaining wall system is an alternative to conventional reinforced concrete retaining wall structures. KeyStone concrete wall units, Tensar geogrid, and compacted soils are combined to form a reinforced soil mass that together act as a gravity wall structure to resist lateral earth pressures and surcharge loads., The objective of this experimental features project is to evaluate the construction and performance of the KeyStone/Tensar retaining wall system. The benefits, as stated by the manufacturer, of this wall system include: design flexibility, easy installation, cost efficient, beauty, and wall face drainage properties., The features of this wall system that were evaluated include: construction (including installation times and labor costs), quality and availability of precast elements, wall costs, aesthetics, wall stability and performance, and appropriateness of design details and parameters., Two walls located in Portland, Oregon were evaluated as part of this research. Wall 1 is approximately 183 feet long, facing Southwest Taylors Ferry Road. The wall has multiple footing steps to accommodate the roadway grade and ranges in height from approximately 2.5 feet to 16 feet. Wall 2 is approximately 190 feet long, fronting on Southwest Bertha Boulevard. The wall has one footing step to accommodate roadway grade and ranges in height from 2.5 feet to 6.5 feet., The KeyStone/Tensar geogrid retaining walls evaluated as part of this project have performed well for two years. Although problems were encountered with block placement during construction of the walls, these problems can be avoided in future projects by designing footing and block placement with consideration of horizontal growth, batter due to block setback and thickness of geogrid., Even though costs were not substantially lower than the estimate for conventional reinforced concrete retaining wall structures, the aesthetic qualities, performance, and construction time make this type of wall an acceptable alternative. Therefore, it is recommended that the KeyStone/Tensar Geogrid retaining wall system be considered as an acceptable alternative to conventional retaining walls for similar installations. Full acceptance of this retaining wall system for use on State projects will require completion of the OSHD Bridge Section's "Wall Acceptance Procedures;" these acceptance procedures are currently being developed.

Railroad ballast consists of open graded crushed stone used as a bed for railroad track to provide stability. Over time, ballast degrades and loses its strength. Fouling of ballast with fines has been a major issue of railway engineering. In this, experimental study, a full-scale railroad section 5 ft in length was constructed with and without geogrid reinforcement. A, full-scale trapezoidal cross-section of a railroad was built. The subgrade was covered with 2 ft of ballast 9 ft wide at the top, and sloped down on both sides on a 2:1 slope. The track panel ties were embedded in the ballast to a depth of 7 in. The, reinforced test section that had geogrid placed 7 in. below the tie performed better than the unreinforced test section in, regards to settlement and fouling of ballast. Settlement of the reinforced test section between the ties and geogrid was, reduced by 37 to 65 percent compared with the settlement of the same portion of the unreinforced test section. The, percentage of rock dust and small diameter particles generated by ballast breakdown beneath the ties was less for the, reinforced test section than for the unreinforced test section.

87-1GT, The considerable increase in using geosynthetics in soil reinforcement made it necessary to develop methods of measuring the interaction properties and modeling load transfer in reinforced-soil structures. The large number of factors that influence the interaction mechanism makes it difficult to standardize the equipment design, testing methodology and data interpretation procedure. The factors are mainly related to the equipment boundary effects, testing conditions, and soil and geosynthetics properties., In order to develop a methodology for evaluating the interface properties of geogrids, a pull-out box and a direct shear box are constructed and instrumented. A testing program is conducted to evaluate the performance of the facility and the effect of different testing parameters (a.g. specimen dimensions, soil thickness, box boundary effects, pull-out rate, soil compaction and relative density, and confining pressure) on the pull-out interaction mechanism of geogrids. Standard equipment design and testing procedure are recommended to overcome most of the limitation in the current practice., A data analysis procedure is established to determine the interface properties and the confined reinforcement characteristics from pull-out test results. The data analysis incorporates the effect of reinforcement extensibility on the soil-geogrid interface mechanism. The interface parameters are evaluated through comparison with the results from tests performed in the large direct shear box.

12-9110, W.O. no. 5H07690H, The objective of this research was to identify a laboratory test method that can be used to quantify improvements in structural capacity of aggregate base materials reinforced with geogrid. For this research, National Cooperative Highway Research Program Report 598 repeated load triaxial, American Association of State Highway and Transportation Officials (AASHTO) T 307 quick shear, and CBR testing protocols were used to test unreinforced and geogrid-reinforced aggregate base materials from northern Utah. Biaxial and triaxial geogrid were investigated in multiple reinforcement configurations. Several statistical analyses were performed on the results of each test method to identify the test that is most likely to consistently show an improvement in the structural capacity of aggregate base materials reinforced with geogrid. The results of this research indicate that, for the methods and materials evaluated in this study, calculation of the modulus at 2 percent strain from the AASHTO T 307 quick shear data is the test method most likely to consistently show an improvement in structural capacity associated with geogrid reinforcement. Of the three configurations investigated as part of this research, placing the geogrid at an upper position within a specimen is preferred. Given that the end goal of the use of geogrid reinforcement is to improve pavement performance, additional research is needed to compare the results of the AASHTO T 307 quick shear test obtained in the laboratory with the structural capacity of geogrid-reinforced aggregate base materials measured in the field. In addition, correlations between the results of the AASHTO T 307 quick shear test and resilient modulus need to be investigated in order to incorporate the findings of the AASHTO T 307 quick shear test on reinforced base materials into mechanistic-empirical pavement design.

ODOT SP&R Item Number 2244, The proposed field study is a continuation of a recently concluded, ODOT-funded project titled: Development of ODOT Guidelines for the Use of Geogrids in Aggregate Bases, which is aimed at addressing the need for improved guidelines for base reinforcement applications. One important objective of this long-term study is to develop a correlation between the index properties of geogrids and their field performance for base reinforcement applications. The index properties that will be studied include the junction strength, low-strain rib strength (i.e. strength at 2%-strain and 5%-strain) and the ultimate rib strength of selected geogrids. The project will involve the selection of a full-depth roadway construction project authorized by ODOT. During the construction of the road subgrade, one test section will be used to examine and compare the performance of selected base course reinforcement geogrid products. The field performance of different geogrids will be monitored using different instruments and monitoring techniques and compared with one another as a function of their index properties. Selected instruments include Earth Pressure Cells (EPC) to measure the stress on the subgrade underneath the geogrid, pore pressure transducers to measure the pore pressure in the subgrade and strain gauges to measure the tensile strength of the different geoshyntetics. The results of this study will help ODOT to develop an improved and expanded set of materials specification guidelines for the use of geogrids in aggregate base reinforcement applications. The outcome of this study will help ODOT and other transportation agencies in the U.S. develop more durable and economical aggregate base designs which will result in longer service life and reduced maintenance costs for the roadways in Oklahoma and across the United States.

LTRC Number: 05-5GT, State Project Number: 736-99-1312, This research study aims at evaluating the performance of base and subgrade soil in flexible pavements under repeated loading test conditions. For this purpose, an indoor cyclic plate load testing equipment was developed and used to conduct a series of large-scale in-box tests and full-scale field tests on several pavement sections., The in-box cyclic plate load tests were conducted to evaluate the performance and benefits of geogrid base reinforcement in flexible pavements. A total of 12 tests were performed on unreinforced and geogrid-reinforced pavement sections. The parameters investigated in this study included the aperture shape (geometry) of the geogrid, location of the geogrid within the base layer, and geogrid tensile modulus. The stress distribution and permanent vertical strain in the subgrade, the development of excess pore water pressure in the subgrade, and the strain distribution along the geogrids were also investigated. The test results showed that the inclusion of geogrids can significantly improve the performance of flexible pavements on weak subgrades [California Boring Ratio (CBR) ≤ 1%], and that the traffic benefit ratio (TBR) can be increased up to 15.3 at a rut depth of 0.75 in. (19 mm). Better performance was observed when the geogrid was placed within the upper one third of the base aggregate layer. The inclusion of geogrid helps redistribute the applied surface load to a wider area on top of the subgrade layer, thus reducing the accumulated permanent deformation within the subgrade., Full-scale field tests were also conducted on several test lane sections built at the Pavement Research Facility (PRF) site using two types of loadings: cyclic plate load test and rolling wheel load test. These sections include blended calcium sulfate (BCS), stabilized BCS, stabilized recycled asphalt pavement (RAP), and stabilized soil as base/subbase materials. The differences in pavement responses of the tested sections to cyclic plate and rolling wheel loads were investigated. The measured rut depth caused by rolling wheel load, in all test sections, were much higher than those measured from the cyclic plate load test. The difference can be as much as 3 to 7 times between these two types of loading. This is mainly due to the effects of principal stress rotation and lateral wander on the permanent deformation of pavements. The field test results also indicate that the cyclic plate load test can be a good performance indicator test for the evaluation and pre-selection of pavement sections for field tests.

DTEH 71-89-509-LA-09, This report documents the construction and initial evaluation of the HaTelit 20/9 Polyester Geogrid material placed at mid-depth of the HMAC overlay of the Broken and Seated PCC pavement on Interstate 10, west of Lake Charles, LA. The roadway has an ADT of 43,400 vpd with 20% of these being heavy trucks. This experimental feature is expected to reduce and limit the severity and extent of pavement distress., The material was placed between the two lifts of Binder Coarse, with an AC tack coat placed on the first lift prior to rolling the material in place. The material was also physically secured by nailing it to the previous lift. The remaining Binder along with the Wearing Coarse was placed over the material., The serviceability of the pavement increased after construction to an average of 4.2 PSI. Cost figures are provided and can be compared to the control sections. The performance of this experimental feature will be monitored over the next three (3) years and will be compared to the two control sections.

LTRC Proj. No. 05-5GT, State Proj. No. 736-99-1312, The inadequacy of many existing roads due to rapid growth in traffic volume provides a motivation for exploring alternatives to existing methods of constructing and rehabilitating roads. The use of geosynthetics to stabilize and reinforce paved and unpaved roadways offers one such alternative. Many studies were conducted to evaluate the improvements associated with geogrid reinforcement of pavements. It is widely believed that geogrid reinforcement of roadways can extend a pavement’s service life and/or reduce the pavement’s structural thickness. LTRC Technical Summary Report 450 September 2009 Several design methods were proposed for flexible pavements with geogrid reinforced base layers. These methods were either based on empirical or analytical approaches. Empirical design methods are usually based on obtaining a performance level from a laboratory model test, which is then extrapolated to the field conditions for design application. The geogrid reinforced design methods based on analytical solution do not address all the variables that affect the performance of these pavements. This report is part of a research study on evaluating the benefits of geogrid reinforcement of base layer in flexible pavements. It presents the findings from laboratory triaxial tests and finite element analyses. Another report of this study will present the findings from large-scale cyclic plate load tests on ALF sections and sections built inside a test box.