Uniaxial Geogrid Research Articles

OVERVIEW OF STUDIES ON EXTERNAL CONFINEMENT OF R/C COLUMNS USING UNIAXIAL GEOGRID

It has been established in the literature that using uniaxial geogrid as internal confinement for reinforced concrete (R/C) columns would improve the strength and ductility characteristics of the column. However, the potential of using uniaxial geogrid as external confinement remains largely unexplored. The aim of the study is to assess the effectiveness of utilizing uniaxial geogrid as external confinement as compared to FRP external confinement, as well as various configurations of internal confinement, including uniaxial geogrid and stirrups. The assessment encompasses the analysis of axial load-displacement behavior, identification of failure modes, and evaluation of structural ductility through metrics such as fracture energy and energy dissipation. Test results indicate significant benefits associated with external confinement using uniaxial geogrid, including strength, ductility, and energy capacity. This study contributes to the progression of knowledge by illustrating the efficacy of uniaxial geogrid as an external confinement method for reinforced concrete columns. Additionally, it offers valuable comparative insights into different confinement techniques, informing the selection and design of optimal strategies for reinforced concrete structures.

OVERVIEW OF STUDIES ON EXTERNAL CONFINEMENT OF R/C COLUMNS USING UNIAXIAL GEOGRID

It has been established in the literature that using uniaxial geogrid as internal confinement for reinforced concrete (R/C) columns would improve the strength and ductility characteristics of the column. However, the potential of using uniaxial geogrid as external confinement remains largely unexplored. The aim of the study is to assess the effectiveness of utilizing uniaxial geogrid as external confinement as compared to FRP external confinement, as well as various configurations of internal confinement, including uniaxial geogrid and stirrups. The assessment encompasses the analysis of axial load-displacement behavior, identification of failure modes, and evaluation of structural ductility through metrics such as fracture energy and energy dissipation. Test results indicate significant benefits associated with external confinement using uniaxial geogrid, including strength, ductility, and energy capacity. This study contributes to the progression of knowledge by illustrating the efficacy of uniaxial geogrid as an external confinement method for reinforced concrete columns. Additionally, it offers valuable comparative insights into different confinement techniques, informing the selection and design of optimal strategies for reinforced concrete structures.

Experimental study on the interface characteristics of geogrid-reinforced gravelly soil based on pull-out tests

The factors influencing geogrid–soil interface characteristics are critical design parameters in some geotechnical designs. This study describes pull-out tests performed on gravelly soils commonly encountered in the Xinjiang region and reinforced with two types of geogrids. The factors affecting the geogrid–gravelly soil interface properties are investigated with different experimental loading methods (pull-out velocity, normal stress), geogrid types, and soil particle size distributions and water contents. The ultimate pull-out force increases with the normal stress and pull-out velocity. Furthermore, with increasing coarse particle content and water content, the ultimate pull-out force increases and then decreases sharply. Based on these research results, this paper provides reasonable parameters and recommendations for the design and pull-out testing of reinforced soil in engineering structures. In reinforced soil structure design, the grid depth should be increased appropriately, and the coarse particle content of the overlying soil should be between 30 and 40%. During construction, the gravelly soil should be compacted to the maximum compaction at the optimal water content, and the structure should have a reasonable waterproofing system. According to the calculation results of the interface strength parameters, the uniaxial geogrid–gravelly soil interface has a high cohesive force csg, which should not be ignored in reinforced soil structure design.

Evaluation of flexural failure for concrete beams partially reinforced by geogrid sheets

ABSTRACT The behavior of reinforced concrete beams with biaxial and uniaxial geogrids as a partial reinforcement with traditional steel bars under flexural loads has been experimentally studied. The effect of geogrid layers with traditional steel reinforcement in concrete beam specimens in compression and tension zones has also been investigated. Geogrid is one of the geosynthetic materials that exhibits both tensile and flexural behavior similar to traditional steel. To examine the effect of geogrids on traditional steel as a composite reinforcement system, strain gauges were fixed to the concrete beams and bottom reinforcement (steel bars). The studied parameters in this investigation are the number of geogrid layers, types of geogrids, and their position in concrete beams. First cracking load, failure load, initial and post-cracking, deflection, and ductility of beam specimen were investigated. The experimental results indicated that using geogrid sheet layers as partial reinforcement greatly contributed to resisting flexural stresses of concrete beams. An increase in the ductility and the capacity load of the concrete beam specimen was also observed. Based on this experimental investigation, the geogrids can be applied as additional or alternative reinforcement with/without traditional steel bars in concrete beams.

In-plane shear behaviour of concrete sandwich panels reinforced with various geogrids

Seismic occurrences have caused severe damage and even the collapse of fragile unreinforced masonry structures. New technologies are replacing these conventional methods of construction; concrete sandwich panels (CSP) are one such technique gaining popularity. In-plane diagonal shear strength of concrete sandwich panels is studied experimentally, and the effect of incorporating geogrids on the deformation capability and load-bearing capacity is reported. Two forms of geogrid material, plastic uniaxial geogrid (PUG) and polyester biaxial geogrids (PBG2 and PBG3) are used to improve the strength and ductility of concrete sandwich panels. Diagonal compression tests have been carried out better to understand the behavior of CSP under in-plane strength. This paper also discusses the effect of the different mixes, the effect of geogrids, load-deformation behaviour, shear capacity, deflection ductility factor, mode of failure, shear strength, and energy dissipation. In contrast to the control specimen, specimens cast with plastic geogrid had a 13.7% and 26% improvement in shear capacity and load-bearing capability for the two types of micro-concrete mixes used in this study. The conclusion reached is that plastic uniaxial geogrid is effective in improving the concrete sandwich panels’ load-bearing capacity, shear capacity, and deformation ability. Polyester biaxial geogrids enhanced the ductility of the concrete sandwich panels.

DURABILITY TESTS OF GEOSYNTHETIC MATERIALS USED IN DIFFICULT ENVIRONMENTAL CONDITIONS

The article describes the ageing process of high-density polyethylene (HDPE) geogrids under the influence of chemical and environmental factors. Research on accelerated ageing of a uniaxial HDPE geogrid incubated in a water solution for a period of 12 months is presented. Three temperatures (25°, 45° and 75°C) were selected for the accelerated ageing tests in aqueous solutions simulating the conditions at a municipal waste landfill. Changes were observed using differential scanning calorimetry (DSC), and correlations with the mechanical properties of the aged geogrid were checked. No significant effect of the loss of antioxidant in the material on the mechanical properties of the uniaxial geogrid was observed. The tests made it possible to determine the mechanical properties, such as tensile strength and deformability of the geogrid – which are extremely important in the analysis of slope stability.

Retaining Wall - Parametric Study of the Method of Reinforcement

Abstract The highway section on the D3 highway Hričovské Podhradie – Žilina – Strážov was carried out on the left branch of the highway body on the overpass and on the right branch on the embankment body. The stability of the embankment body was ensured by a geosynthetics reinforced retaining wall. The retaining wall was assembled from reinforced concrete prefabs, on which the uniaxial geogrids were attached. The article presents a numerical analysis of the deformations of this reinforced structure in the profile monitored by geotechnical monitoring. The results of the numerical analysis of the deformations of the retaining wall were confronted with geotechnical monitoring measurements. Geotechnical monitoring measurements confirmed the reality of the numerical model of the retaining wall. Verification of the reality of the numerical model of the retaining wall made it possible to use this model for a parametric study of the influence of the reinforcement method on the deformation of the face of the reinforced retaining wall. In the parametric study, the effects of the change in the horizontal length and vertical spacing of the reinforcement elements, as well as their interaction with the backfill soil on the deformation values of the face of the retaining wall are analyzed.

Study on Interface Interaction between Uniaxial Geogrid Reinforcement and Soil Based on Tensile and Pull-Out Tests

The interaction between reinforcement and soil is a key problem in the application of geosynthetics as reinforcement in geotechnical engineering. In this study, tensile and pull-out tests on a uniaxial geogrid were carried out using self-designed tensile and pull-out test equipment. The tensile test evaluated the tensile load–strain characteristics of a geogrid. Under the condition of lateral confinement, the tensile force and secant tensile stiffness of the geogrid increased with an increase in the normal stress when the strain was constant, and the secant tensile stiffness decreased with a decrease in the tensile rate. The stiffness coefficient was used to quantitatively describe the change in the stiffness of the reinforcement. Using the pull-out test, the variation laws of the pull-out force of the geogrid under different normal stresses and different longitudinal rib percentages were obtained. When the geogrid was broken, the pull-out force of the same type of geogrid was not significantly different under different normal stresses. With an increase in the longitudinal rib percentage, the pull-out force of the geogrid under the same normal stress gradually increased, and the apparent friction coefficient was obtained by analysis. The results of the apparent friction coefficient obtained by the analytical method in accordance with French specifications (NF P94-270-2020) are relatively safe compared to the experimental values.

Pullout testing and Particle Image Velocimetry (PIV) analysis of geogrid reinforcement embedded in granular drainage layers

The paper investigates the feasibility of using fine-grained soil as backfill material of geosynthetic-reinforced walls and slopes, through a laboratory study on pullout behavior of geogrids in granular layers. A series of pullout tests was carried out on an HDPE uniaxial geogrid in thin sand and gravel layers that were embedded in clay specimens.Aside from different soil arrangements, the influences of moisture content and overburden pressure on the geogrid pullout behavior is assessed and discussed. The tests were carried out at four different gravimetric water contents (GWC) on the dry and wet sides of the clay optimum moisture content (OMC), and overburden pressure values within the range σv = 25–100 kPa. Particle Image Velocimetry (PIV) was used to capture digital images during the tests, which were processed to help with the interpretation and improved understanding of the soil-geogrid interactions at different GWC values. Results show that embedding geogrid reinforcement in layers of sand or gravel can significantly increase the pullout resistance in an otherwise moist clay backfill, and this improved pullout efficiency is greater at higher overburden pressures. The improvement in pullout capacity was observed in clay specimens compacted at both the dry and wet sides of the OMC.

Pullout Characteristics and Damage Softening Model of the Geogrid-Soil Interface

The mechanical properties of geogrid-soil interface is very important in design and stability analysis of reinforced soil structure. In order to study the complicated mechanism of geogrid-soil interface, a series of pullout tests of HDPE uniaxial tensile geogrids with the different transverse ribs spacing is used to investigate the interaction characteristics in the laboratory. The test results show that pullout force and displacement curves are characterized as strain softening; compared with the no-reinforced case, the case reinforced with geogrid has larger cohesion and lower friction angles. The ductility of soil is enhanced due to geogrid reinforcement. Based on the basic control equations of the interface and damage theory, trilinear shear stress-displacement damage softening model is proposed to describe the strain-softening characteristics of geogrid-soil interface. Analytical solutions of interface tension, shear stress, and displacement at different stages are derived considering strain softening based on damage, and the development of shear stress and progressive failure mode of the geogrid-soil interface at different pullout stages is revealed. Furthermore, the proposed model is verified by experimental results.

Flexural Performance of Cement-Treated Sand Reinforced with Geogrids for Use as Sub-Bases of Pavement and Railway Structures.

Cement-treated sand (CTS) exhibits undesirable brittle behavior after the applied stress reaches its peak strength. This research investigates the flexural behavior of CTS that is reinforced with uniaxial geogrid (CTSG). A total of 6% cement content was mixed with sand. Uniaxial geogrids with three different strengths were utilized to create the CTSG samples. The number of reinforcement layers, including single and double reinforcements, was studied. The image processing method was applied to analyze the surface cracks in the specimens. The results show that the geogrid type and the number of reinforcement layers affect the flexural behavior of the CTSG. Geogrid reinforcement changed the behavior of the CTS from a brittle material to a semi-brittle or ductile material because the residual tensile stresses were carried by the geogrids. The high-strength geogrid with a double reinforcement layer proved to be most effective in enhancing the peak strength and toughness with improvement ratios of 1.80 and 11.7, respectively. Single and double reinforcement layers with all geogrid types can reduce surface cracks with average crack reduction ratios of 64% and 83%, respectively. The CTSG can be successfully used as a sub-base layer to increase flexural performance and the lifetime of pavement and railway structures.

Evaluation of interaction properties of uniaxial geogrids with waste foundry sand

The reuse of waste materials can help alleviate problems related to placing them in landfill and can also preserve fast dwindling natural granular materials. Waste foundry sand (WFS) can be a promising candidate as a backfill material in the construction of mechanically stabilised earth (MSE) walls. In the design of such MSE structures, the interaction properties between WFS and geogrid reinforcement are important input parameters. In the present study, the interaction properties of a wide range of different polyester (PET) uniaxial geogrids with WFS in two common modes – direct shear and pullout – were evaluated using large-size interface direct shear and pullout tests. In the pullout mode, the interaction of the geogrid embedded in WFS under axial and transverse pullout was studied. The direct shear interface coefficients of four PET geogrids with WFS were found to be in the range observed in conventional fill materials. Higher axial and transverse pullout resistance factors were observed for geogrids with higher tensile strength and higher opening area ratio. Empirical equations were proposed to estimate the axial and transverse pullout resistances of geogrids at two pullout displacements. Finally, sensitivity analyses were carried out to identify the parameters significantly influencing the axial and transverse pullout resistances of geogrids in WFS.

Deformation mechanism and soil evolution analysis based on different types geogrid reinforced foundation

Geogrids are extensively used to improve the bearing capacity of low strength soil and reduce the settlement of soft soil foundations. This study aims to compare the bearing capacity and deformation characteristics of geogrid reinforced foundation with different types of geogrids (uniaxial, biaxial, triaxial) and different reinforcement layers (N = 1, 2, 3) in reduced-scale transparent soil model tests. The images of the foundation model are captured by the laser transmitter and digital camera. These images are further analyzed to study the foundation deformation of different cases by digital image processing technique. The results show that triaxial geogrid reinforced foundation has a better bearing capacity than the uniaxial geogrid and biaxial geogrid reinforced foundation. In the process of foundation settlement, the slip crack surface and ground heave gradually develop with the bottom-up diffusion of horizontal and vertical displacements of the soil. Local shear failure first occurred in the bottom of the foundation, and then transformed into general shear failure. These results visualize and quantify the soil displacement transfer and spreading behavior in geogrid reinforced foundations. This paper illustrates the effects that geogrid reinforcing at a microscopic scale under strip footing loads.

Mechanical and hydraulic compatibility of RAP with geosynthetics used in MSE walls

Mechanical and hydraulic properties of recycled asphalt pavement (RAP) as backfill in mechanically stabilized earth (MSE) walls were evaluated. Woven and nonwoven geotextiles and uniaxial and biaxial geogrids were used as reinforcements. Results of interface direct shear tests showed that the interface friction angle (δ) of RAP-geogrid was higher than that of RAP-geotextile. On average, the δ for RAP-biaxial geogrid was 15% higher than δ for RAP-uniaxial geogrid. For geotextile reinforcement, the δ for RAP-woven geotextile was 20% higher than δ for RAP-nonwoven geotextile. Compaction of RAP at elevated temperatures only slightly affected δ. Pullout capacities of RAP-uniaxial geogrid and RAP-woven geotextile are comparable to those of sand-uniaxial geogrid at different overburden pressures. The compacted RAP reinforced with uniaxial geogrid, however, exhibited significant creep strains at a range of sustained pullout forces that led to failure of the RAP-uniaxial geogrid. Reducing the pullout capacity by 40% is recommended for design to reduce the potential of creep failure. Long-term filtration tests showed that in all cases RAP-geosynthetic systems were able to drain freely and this behavior could be predicted with the existing clogging criteria that have been previously developed for sands and gravels.

Comparative study of various flexible facing materials for soil nailed slopes

As the natural slopes along the roadsides and embankments are not stable due to sliding or collapse, a technique termed “soil nailing” is used to stabilize the natural or man-made slopes. A small scale physical model of soil nailed slope in well-graded sandy soil and inclined at 60° to the horizontal using four number of soil nails is prepared in the laboratory using different flexible materials as flexible facing namely Uniaxial Geogrid, Geotextile fabric, Coir mat, Fine Stainless steel woven wire mesh. The results of these soil nailed slopes with flexible facing materials and the soil nailed slopes with no additional facing are compared. The behavior of these soil nailed slopes is analyzed by applying extra surcharge with the help of a hydraulic jack for load application on the physical model. The strain produced in the inserted soil nails on stress application is determined using a multimeter with the help of the sensors bonded to the each soil nail. Also, the deflection of the soil mass in horizontal and vertical deflection is measured as it is clearly visible from the perplex sheet provided on the outline of the physical model. The stress, horizontal displacement and vertical displacement induced in all the materials is measured and compared. The fine stainless steel wire mesh took the maximum stress of 1.23 N/mm2 with minimum displacements and minimum strength of 0.492 N/mm2 was possessed by the slope without any facing material. Also, the other flexible materials like uniaxial Geogrid and coir mat possessed good strength and hence can be an effective alternate to strengthen existing or new slopes and provision of flexible facing materials in soil nailing technique further aids in slope stabilization.

Geosynthetic Reinforced Fill Material for Tennessee Bridge Approach Slab Support

The approach slab is constructed at bridge ends to serve as a smooth transition from the highway pavement to the bridge deck. However, motorists usually complain about a sudden change in elevation (bump) at the highway/approach slab (H/S) joint that causes a potential hazard for public safety, damage to vehicles, and rider discomfort. This paper develops a finite element (FE) analysis for the differential settlement at the H/S joint when supported by a strip footing that sits on compacted layers of soil embankment with uniaxial geogrid reinforcement. A parametric study was conducted to select the optimum design that consists of five geogrid layers equally spaced within a depth of 2 [Formula: see text] below the strip footing, where [Formula: see text] is the width of the footing. The inclusion of geogrid reinforcement did not only enhance the ultimate bearing stress of the strip footing but also redistributed the vertical loads over a wider region of soil embankment and thus reduced settlement. A case study is also presented for modeling the performance of a preliminary design proposed by Tennessee Department of Transportation (TDOT) for the retrofit of bridge ends. The FE analysis showed a 30%–40% improvement in the ultimate bearing stress of the strip footing when the geogrid reinforcement proposed by TDOT is extended to a depth of 1.5 [Formula: see text] below the footing.

Polymer Geogrids: A Review of Material, Design and Structure Relationships.

Geogrids are a class of geosynthetic materials made of polymer materials with widespread transportation, infrastructure, and structural applications. Geogrids are now routinely used in soil stabilization applications ranging from reinforcing walls to soil reinforcement below grade or embankments with increased potential for remote-sensing applications. Developments in manufacturing procedures have allowed new geogrid designs to be fabricated in various forms of uniaxial, biaxial, and triaxial configurations. The design flexibility allows deployments based on the load-carrying capacity desired, where biaxial geogrids may be incorporated when loads are applied in both the principal directions. On the other hand, uniaxial geogrids provide higher strength in one direction and are used for mechanically stabilized earth walls. More recently, triaxial geogrids that offer a more quasi-isotropic load capacity in multiple directions have been proposed for base course reinforcement. The variety of structures, polymers, and the geometry of the geogrid materials provide engineers and designers many options for new applications. Still, they also create complexity in terms of selection, characterization, and long-term durability. In this review, advances and current understanding of geogrid materials and their applications to date are presented. A critical analysis of the various geogrid systems, their physical and chemical characteristics are presented with an eye on how these properties impact the short- and long-term properties. The review investigates the approaches to mechanical behavior characterization and how computational methods have been more recently applied to advance our understanding of how these materials perform in the field. Finally, recent applications are presented for remote sensing sub-grade conditions and incorporation of geogrids in composite materials.

Calculation Formula for the Pullout Force of Uniaxial Geogrid-Reinforced Expansive Soil

To obtain the action force between the reinforcing material and filler in reinforced soil, many scholars at home and abroad have conducted pullout tests, which are limited by the testing apparatus. Most of them have studied the pullout force between a biaxial geogrid and sand. The pullout force formula is generally believed to be composed of the surface friction and lateral resistance of transverse ribs, and uniaxial geogrids have rarely been researched experimentally on the basis of the pullout force between them and the expansive soil filler due to the large distance among transverse ribs. This study draws on existing methods to determine the pullout force, conducts a preliminary analysis, proposes a formula for calculating the maximum pullout force, uses a self-developed large-scale CNC pullout test system, and utilizes its large size, bidirectional airbag loading, and ability to eliminate side wall friction. The design of the test scheme is optimized to obtain two important calculation parameters in the formula: one is to cut grids of different lengths to provide lateral resistance and then implement them to obtain the coefficient of sliding friction between grid and fill; the other is to develop different numbers of horizontal ribs in the pullout test of a grille, and the lateral resistance of the end bearing of a single transverse rib is measured. The results of the lateral resistance of the end bearing based on the analysis of the three mechanisms of shear, punching, and Prandtl failures are compared. The lateral resistance of the lateral rib end bearing measured from the test is proven reasonable. Two types of expansive soils reinforced by different types and sizes of grids are analyzed with the calculation formula of the maximum pullout force, and the coefficient of pullout friction is determined to be rational. The research results can be used to guide the design and construction of uniaxial geogrid-reinforced expansive soil and the modification and upgrading of products by grid manufacturers.

Axial Pullout Resistance and Interface Direct Shear Properties of Geogrids in Pond Ash

Presently, pond ash is accumulated in large quantities in thermal power plants. There is potential for large-volume utilization of pond ash as a fill material. Applications involving mechanical stabilization of fills constructed with geogrid-reinforced pond ash is explored in the study. A systematic experimental program was carried out to evaluate the interface direct shear strength and axial pullout resistances of four to eight different uniaxial polyester geogrids embedded in pond ash. Geogrids of varying tensile strengths and opening area ratios were considered. No significant difference in the interfacial shear strengths was observed among the four different geogrids tested. Based on the interface direct shear strengths at peak and critical states, the efficiencies of geogrids were found to range from 62 to 83%. The axial pullout resistances of geogrids in pond ash were found to be high for grids with high tensile strength. Finally, based on extensive pullout test results, empirical equations were fitted to estimate the axial pullout resistance of uniaxial geogrids embedded in pond ash corresponding to two front-end axial pullout displacements of 30 mm and 60 mm. The proposed equations were found to agree very closely with the experimental results (R2 = 0.95).

Flexural Behavior Analysis and Design Approach for R.C. Beams by Hybrid Reinforcement of Steel Rebars and HDPE Uniaxial Geogrids

Abstract The objective of this study is to investigate a hybrid reinforcement method for concrete beams, which consists of steel rebars and HDPE (high-density polyethylene) uniaxial geogrids, by developing an experimental comparative investigation between utilizing different grades and layers of HDPE uniaxial geogrids as the primary reinforcement or as extra reinforcement to the steel rebars. The experiments for this investigation included 24 reinforced concrete beams in order to provide rich data for the flexural behavior analysis and design approach. For a detailed analysis, strain gauges were connected to steel rebars and HDPE uniaxial geogrids. Analysis of the results shows that the hybrid reinforcement method using steel rebars and HDPE uniaxial geogrids provided greater benefits (such as energy absorption capacity, ductility index, ultimate load, and steel-yield load) and more effective utilization (such as better flexural performance, lower deformation values corresponding to the steel-yield load, and greater benefits to cost ratios) than utilizing HDPE uniaxial geogrids as the primary reinforcement or utilizing the conventional reinforcement of steel rebars. Simple design equations were added to calculate the flexural bending capacity, the necessary HDPE uniaxial geogrids’ grade, and the number of layers utilizing the HDPE uniaxial geogrids as the primary reinforcement or as extra reinforcement to the steel rebars.