Effect Of Geogrid Reinforcement Research Articles

Temperature-Dependent Post-Cyclic Mechanical Characteristics of Interfaces between Geogrid and Marine Reef Sand: Experimental Research and Machine Learning Modeling

The mechanical response of the marine reef sand–geogrid (RG) interface can be influenced by a high-temperature climate, grain size, and variable stress environments. These factors are critical to the effectiveness of geogrid reinforcement in reef sand engineering. However, there are few studies on the influences of grain size, temperature, and stress history on the mechanical characteristics of RG interfaces, with most studies centering on the influence of single factors on the mechanical characteristics of RG interfaces. In this paper, based on self-developed temperature-controlled large interface shear equipment, a series of before/post-cyclic shear tests were carried out on RG interfaces in the temperature range of 5–80 °C. The impact of different reef sand grain sizes on the RG interface was explored (S1: 1–2 mm; S2: 2–4 mm). It was shown that temperature and grain size had significant influences on the mechanical characteristics of the RS interface. Compared with the S1 RG interfaces, the S2 RG interfaces had higher sensitivity to temperature changes with respect to the before/post-cyclic maximum shear strength. Moreover, in comparison to the before-cyclic shear strength, the post-cyclic maximum shear strength is more responsive to temperature changes. The before/post-cyclic maximum shear strength of the S2 RG interfaces was greater than the maximum shear strength of the S1 RG interfaces as the temperature changed. Based on the results of physical tests, a machine learning model containing 450 datasets was constructed, which can accurately predict the shear strength of the RG interface.

INTERACTION BETWEEN GEOGRID REINFORCEMENT AND STONE AGGREGATES MIXED WITH TIRE-DERIVED AGGREGATES

The disposal of discarded tires creates a major problem, as they are non-biodegradable and occupy huge landfill space. The scrap tires can be utilized in civil engineering applications as an alternative material by partial or complete substitution of conventional materials. In many of these applications, scrap tires are not utilized directly; instead, they are shredded to produce a material known as tire-derived aggregate (TDA). In this study, an attempt is made to understand the interaction between geogrid reinforcement and stone aggregates mixed with TDA using a large-scale triaxial test with a specimen diameter of 150 mm and height (Hs) of 300. The geogrid reinforcement is placed at a spacing of Hs/2, Hs/3, Hs/4, and Hs/5 along the length of the sample. The results are analyzed to understand the effect of geogrid reinforcement on stone aggregate mixed with TDA, and it is noticed that the deviatoric stress increases with the inclusion of geogrid reinforcement in the mix proportion.

INTERACTION BETWEEN GEOGRID REINFORCEMENT AND STONE AGGREGATES MIXED WITH TIRE-DERIVED AGGREGATES

The disposal of discarded tires creates a major problem, as they are non-biodegradable and occupy huge landfill space. The scrap tires can be utilized in civil engineering applications as an alternative material by partial or complete substitution of conventional materials. In many of these applications, scrap tires are not utilized directly; instead, they are shredded to produce a material known as tire-derived aggregate (TDA). In this study, an attempt is made to understand the interaction between geogrid reinforcement and stone aggregates mixed with TDA using a large-scale triaxial test with a specimen diameter of 150 mm and height (Hs) of 300. The geogrid reinforcement is placed at a spacing of Hs/2, Hs/3, Hs/4, and Hs/5 along the length of the sample. The results are analyzed to understand the effect of geogrid reinforcement on stone aggregate mixed with TDA, and it is noticed that the deviatoric stress increases with the inclusion of geogrid reinforcement in the mix proportion.

Effects of subgrade spatial variability on critical strains and effectiveness of geogrid reinforcement in flexible pavement

The objective of this study is to assess the impact of spatial variability in the subgrade layer on the critical response of pavements and the effectiveness of geogrid reinforcement, employing the random field finite difference analysis (RFFDA). A comprehensive parametric study was conducted to examine the influence of two crucial factors: the coefficient of variation (COVE\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\ ext{COV}}}_{E}$$\\end{document}) and scale of fluctuation (SOF) of the subgrade modulus. Further investigation was conducted to uncover the statistical and mechanical mechanisms underlying the impact of subgrade spatial variability with emphasis on the critical strain distributions and their correlation with both the overall modulus and the local spatial variability of the key influence zone. Furthermore, this study explored the influence of subgrade spatial variability on the effectiveness of geogrid in reducing critical strains, considering various placement positions and geogrid moduli. The following main conclusions are drawn: (a) subgrade spatial variability has a substantial amplifying effect on critical pavement strains due to low modulus dominating effect, (b) there exists a worst value of SOF that results in the most unfavorable statistics of critical subgrade strain, (c) the effect of subgrade spatial variability on critical subgrade strain is more pronounced compared to its effect on critical asphalt strain, (d) the mean value of critical subgrade strain in RFFDA can be significantly underestimated when assuming fixed location for the strain, and (e) the effectiveness of geogrid in reducing critical strains is impacted by subgrade spatial variability, with the impact varying with the type of critical strain and geogrid location. Specifically, when placed at the base course–subgrade interface, the ability of geogrid to reduce critical subgrade strain is significantly compromised due to the subgrade spatial variability.

Finite Element Modelling of Geogrids Reinforced Ballasted Tracks

This paper presents results obtained from three-dimension finite element modelling (FEM) to study the effects of geogrids on the deformation responses of ballasted tracks. In this study, a series of numerical simulations are carried out on track sections with and without the inclusion of geogrids. Sensitivity analysis was carried on parameters affecting the performance of geogrid, including the axial stiffness, interface property and the location of geogrid placement in the track substructure. The tracks are subjected to moving train loading under 150 kN wheel load travelling at a given speed of 72 km/h. Based on simulation results, it is found that geogrid provides a reinforcing function to rail track primarily in the form of confinement which resulted in reduced lateral displacement in a reinforced track compared to a traditional track. A significant reduction in vertical and lateral displacement is found from the inclusion of a geogrid layer at the ballast and capping interface while the effect of geogrid reinforcement is more pronounced with increased loading cycles. The effects of geogrid stiffness, interface conditions and geogrid placement are studied and it is found that the axial stiffness of geogrid is found to impact overall track deformation while the optimum placement of geogrid is found to directly at the ballast and capping interface.

On the effect of subgrade strength on the performance of geogrid-reinforced railway ballast

This paper presents the results of a series of ballast box tests aimed at investigating the effectiveness of geogrid reinforcement in reducing track settlement in a 300mm-thick layer of railroad ballast supported by three different artificial subgrades. In each experiment, the ballast layer supports a model tie subjected to cyclic compressive loading applied at a frequency of 0.8Hz with stress extrema at the tie-ballast interface of 57kPa and 400kPa for a total of 40,000 cycles. The three artificial subgrades considered in this study have CBR readings of 25, 13, and 5. For each subgrade, four tests are performed whereby one corresponds to an unreinforced condition (i.e., no geogrid) and three are reinforced with a single geogrid placed at either 150mm, 200mm, and 250mm below the bottom of the tie. The results indicate that geogrids exhibit a superior ability to minimize the tie’s settlement when the ballast layer is supported by a weak subgrade. The experiments further allude to the fact that the influence of the geogrid’s placement depth is exacerbated by the subgrade’s strength. In ballast layers supported by competent subgrades, the geogrid placement depth wields a marginal influence on the resulting tie settlement. However, the geogrid’s location becomes a key factor in ballast beds underlain by soft subgrades, with geogrids placed closer to the bottom of the tie being the most effective at minimizing the tie settlement.

Effect of Geogrid Reinforcement and Soil Relative Density on Performance and Contact Pressures of Ring Foundations on Sand

Reinforcing soil beneath foundations is one of the standard methods to improve the foundation performance. However, soil relative density may affect the efficiency of reinforcement. This experimental study has been conducted on a model ring foundation resting on medium, dense, and very dense geogrid-reinforced sand. For this purpose, 17 tests were carried out to evaluate the effect of soil density and reinforcement depth and size on bearing capacity and settlement of the ring foundation and its normal contact pressure distribution. The results show that geogrid-reinforced sand with higher relative densities improves bearing capacity and decreases settlements significantly. It can be shown that implementing a geogrid layer that is equal to the dimensions of the footing is cost-effective. The scale effect analysis has been conducted for the model foundation, sand, and geogrid used in this research. Additionally, normal contact pressure distributions for unreinforced and reinforced sand are presented. Decreasing the depth of reinforcement transforms the form of normal contact pressure distribution from saddle to parabolic.

Experimental Study on Subgrade Stabilization Using Geogrid and Perlite

Abstract: This paper presents the summary of experimental program to evaluate the soil stabilized with perlite and the geogridreinforcement. Due to its pozzolanic properties, perlite, a glassy volcanic rock, may be utilised as a stabilising agent. The standard California bearing ratio (CBR) laboratory tests were performed on the soil samples with various combinations of perlite and single layer of geogrid reinforcement placed at various height. The laboratory experiments were undertaken to investigate the impact of using perlite (0%, 10%, 20%, 30%) and geogrid (single layer of geogrid reinforcement placed at H/2, 3H/4 and H/4). The effect of geogrid reinforcement with respect to the position and varying contents of perlite on the strength behaviour of subgrade soil has been examined. Furthermore, the test was carried out by optimum percentage of perlite with geogrid placed at optimum height. Results of the current study indicate that there is a significant increase in CBR values for subgrade soil stabilized with perlite and reinforced with geogrid. Maximum CBR value was observed in the soil sample reinforced with single geogrid layer placed at H/4 (where H is height of CBR mould) with 20% perlite

Effects of Geogrid Reinforcement on the Backfill of Integral Bridge Abutments

The construction of integral bridges is one of the most effective methods to reduce bridges’ construction and in-service costs. However, there are associated geotechnical problems with their abutments backfill due to the integrated abutments. The main goal of this study is to evaluate and quantify the benefits of geogrid reinforcement for reducing the backfill’s geotechnical problems. For this purpose, using small-scale physical modeling, the benefits of geogrid reinforcing of the backfill of an integral abutment bridge subjected to cyclic movements are evaluated. The results are then compared with a previous study performed on unreinforced backfill and two types of geocells. In this study, 120 loading cycles are applied to geogrid-reinforced soil to simulate the cyclic loadings on integral abutment backfill due to seasonal abutment displacement. The horizontal reaction load at the top of the wall, changes in pressure behind the wall, and deformation in backfill soil are measured during the test. Then the results are discussed in terms of equivalent peak lateral soil coefficient (Kpeak), lateral earth pressure coefficient (K*), and normalized settlement behind the wall (Sg/H). The derived lateral soil coefficients and settlement behind the abutment show that geogrid substantially reduces pressure and settlements after 120 cyclic loads. Based on the results, Kpeak and K* of the geogrid-reinforced backfill decrease by up to 36%, and Sg/H behind the wall decreases by 62%. In addition, the comparison of the results for geogrid with two geocell types shows that geogrid is more efficient in terms of lateral soil coefficients.

Effects of particle breakage on the mechanical characteristics of geogrid-reinforced granular soils under triaxial shear: A DEM investigation

A series of numerically triaxial shear tests on crushable and uncrushable granular soils reinforced by geogrid were conducted using 3-Dimension Particle Flow Code. The macroscopic behaviors of crushable and uncrushable granular soil during shearing were compared. Also, the underlying macro–micro linkages were explored. The main findings are as follows: Particle breakage decreases the contact forces between soil particles to reduce the shear strength of granular soils; The reinforcement effect of geogrids on the shear strength of granular soils can be attributed to the increase in fabric and force anisotropies; The particle displacement distribution of crushable soil samples is more uniform than that of uncrushable samples, and the shear band of crushable samples is not obvious; The reinforcement effect of geogrid with the aperture size ratio of 4.4 is the highest among the samples because the number of crushed particles and the deformation of geogrids reaches a balance.

The effect of geogrid reinforcement of embankment over soft foundation

This paper deals with the usage of geogrids for soil improvement utilizing the PLAXIS 3D FE program's numerical analysis approach. Because of the low shear strength and instability of soft clay soils, reinforcement has been used to improve clay soils. The reinforcement mechanism was analyzed on the basis of results and output. The results of the program outputs are shown in PLAXIS. The reinforcement has little effect in the case of horizontal displacement and vertical displacement, but only a significant effect on the safety factor. This paper also deals with improving soft clay soil using stone columns. The main objective is to reduce settlement and increase the carrying capacity of the soil and shorten the consolidation period. The work investigates geogrid-reinforced stone columns that improved the behavior of soft clay soils under the influence of loading and construction. Underwent soil the stone columns testing covered with a geogrid and traffic load of 50 kpa. The improved method of using stone columns and PLAXIS 3D was used to create the FE model. The results concluded that the comparison results gave an improvement rate of up to 50 % of the improvement for the stone-column-reinforced clay soil in the construction phase.

Effect of geogrid reinforcement on tensile failure of high-strength self-compacted concrete

In this study, the tensile strength, failure mechanism and ductile behaviour of geogrid-reinforced high-strength self-compacting concrete discs subjected to both the Brazilian tensile strength test and a biaxial compressive test are studied. To determine the combined effects of geogrid layer numbers and inclination angle on the ultimate tensile strength of concrete samples, 21 experiments were conducted with up to three layers of geogrids inclined at angles of 0° to 90°, at increments of 15°. In addition, discrete-element numerical simulations were conducted using two-dimensional particle flow code to examine the failure behaviour of geogrid-reinforced high-strength self-compacting concrete discs. The numerical models were first calibrated by the experimental results and then the failure behaviour of models containing geogrids was investigated. Both experimental and numerical results demonstrate that augmenting the concrete discs with geogrids increases the ductility of specimens, especially after failure. As the number of geogrid layers increased, the tensile strength of specimens also increased, whereas the tensile strength and absorbed energy were the same for specimens with different numbers of geogrid layers and inclination angles of 75° and 90°. The specimen with three horizontal geogrid layers had the highest tensile strength, biaxial compression strength and ductility of all specimens tested.

Effect of geogrid reinforcement on the load transfer in pile-supported embankment under cyclic loading

This paper investigated effects of geogrid reinforcement on the load transfer in pile-supported embankment under cyclic loading using self-moving trapdoor tests. In the self-moving trapdoor test setup, the trapdoor between two stationary portions (which were equivalent to the piles) was supported by compression springs to simulate the subsoil. Quartz sand and a biaxial geogrid were used as the test fill and reinforcement material, respectively. Tests results show that soil arching above the geogrid reinforcement and load transfer to the stationary portions (caused by the soil arching and tensioned membrane effect) experienced a process of “relatively enhancing - relatively degrading” with an increase in the number of cycles and maintained similar degrees within each complete cycle of cyclic loading. Moreover, the inclusion of geogrid reinforcement reduced the mobilization of soil arching, but increased the degree of load transfer to the stationary portions. In addition, cyclic loading with a higher frequency tended to mobilize more soil arching and induce a higher degree of load transfer to stationary portions. Also observed was that a higher frequency cyclic loading tended to decelerate the degradation of load transfer to stationary portions and caused less surface settlement, which indicating increased load-carrying capacity of pile-supported embankment.

Membrane Effect of Geogrid Reinforcement for Low Highway Piled Embankment under Moving Vehicle Loads

In this paper, the membrane effect of geogrid reinforcement was investigated based on numerical simulation to understand the serviceability and deformation of highway piled embankments under moving vehicle loads. The membrane effect of geogrid reinforcement in low embankments (i.e., the ratio of embankment height to pile spacing is less than 1.5) was clearly emphasized. It has been found that the maximum settlement of geogrid occurs in the central area between the piles, and the maximum tension was concentrated at the corner of the pile cap. Due to the attenuation of the soil arching effect under moving dynamic loads and the punching mechanism, the settlement and tension of the geogrid increased considerably by approximately 35% and 23% compared to those under static loads. A parametric study was also achieved, and the results presented that the geogrid reinforcement tension increased by increasing the pile spacing, embankment height and geogrid stiffness, vehicle wheel load and vehicle velocity. It was also found that the reinforcement tension was most sensitive to the pile spacing among all the parameters considered in this paper, whose magnitude increased by approximately 104% as the pile spacing increased from 2.0 m to 2.5 m under dynamic loads.

Experimental Study on Strength Behaviour of Geogrid Reinforced Subgrade Soil

This paper presents the summary of experimental program to evaluate the potential of KOBM (Klockner Oxygen Blown Maxhutte) slag to stabilize the geogrid-reinforced subgrade soil in Suva, Fiji. This KOBM slag is a by-product of steel manufacturing process in New Zealand. The standard California bearing ratio (CBR) laboratory tests were performed on the soil samples with various combinations of geogrid and KOBM slag, along with other geotechnical tests to determine the strength behaviour of subgrade soil. The laboratory experiments were undertaken to investigate the impact of using KOBM slag (0%, 5%, 10%, 15%, 20%) with single and double layers of geogrid reinforcement placed at H/2 and H/4 (where H is height of CBR mould) in the soil sample. The effect of geogrid reinforcement with respect to the position and number of layers with varying contents of KOBM on the strength behaviour of subgrade soil has been examined. Results of the current study indicate that there is a significant increase in CBR values for subgrade soil stabilized with KOBM and reinforced with geogrid. Maximum CBR value was observed in the soil sample reinforced with single geogrid layer placed at H/2 with 20% KOBM slag. This is the best outcome amongst all the combinations of KOBM, position/no. of layers of geogrid reinforcement in the current experimental study consisting of 50 experiments.

Effects of geogrid reinforcement on the seismic performance of lightweight embankments

Highway embankments have experienced earthquake induced damages from minor to catastrophic scales during the past few decades despite the fact that highways are considered as major lifelines that should be in continuous operation under any circumstances. Recent advances in highway engineering suggest that geosynthetic reinforcement can be considered as a novel approach to mitigate the earthquake hazards on highway embankments successfully. The use EPS geofoam inclusions is one of the prominent improvement methods available to increase the seismic performance of lightweight embankments. It’s a well-known method to reduce the magnitude of earthquake-induced dynamic forces. The aim of this numerical study is to determine the effects of using geogrid reinforcement on the seismic performance of lightweight embankments. Non-linear dynamic analyses were performed using the PLAXIS software using real earthquake records. Evaluation of the results reveal that inclusion of geogrid reinforcement layer beneath the lightweight embankment model successfully decreases earthquake-induced dynamic forces and increases the seismic performance of the embankment model in comparison of the nominally identical structure with no geogrid reinforcement. Numerical results obtained from this novel technique suggest that the implementation of a geogrid layer beneath such lightweight embankments can successfully and effectively increase the seismic performance of such structures.

Reinforcement Effect Investigation of Geogrids in the Junction between New and Existing Subgrades in Highway Widening

Abstract To investigate the reinforcement effect of geogrids with different laying schemes in subgrade widening, one tested road was selected in northern China, and the subgrade deformation and the geogrid strains were analyzed by field testing, the centrifuge model test, and numerical calculation. It was revealed that the geogrid strain of the construction period was mainly derived from the roller’s compaction. The addition of the geogrid is helpful to prevent shear sliding of the new subgrade. In the centrifugal model test and numerical calculation, the geogrid reinforcement was proved to be effective in reducing the settlement of the new subgrade, but little effect to the existing one. Strain of the lower geogrid layer was generally larger, and the connection line of maximum strain points in each layer is close to the shear-sliding location of the new subgrade. The reinforcement effect of different geogrid layers changed noticeably, and the bottom one played a major role in withstanding the tensile stress.

Bearing Capacity of Eccentrically Loaded Strip Footing on Geogrid Reinforced Sand

This study aims to demonstrate the effects of geogrid reinforcement on the bearing capacity of strip footing under eccentric loading. Numerical analysis using finite element program called (PLAXIS 2D Professional v.8.2) are presented. The effect of each of the depth ratio of the topmost layer of geogrid (u/B), the vertical distance ratio between consecutive layers (h/B), number of geogrid layers (N), and the effective depth ratio of reinforcement (d/B) on the bearing capacity were studied, where (B) is the footing width. Also, the combined effect of load eccentricity ratio (e/B), depth of embedment ratio of footing ( f D /B) and the angle of internal friction ( ) on the ultimate bearing capacity were investigated.

Test Studies on Geogrid–Soil Interface Behavior under Static and Dynamic Loads

Pullout tests on geogrids have been regarded as the most direct way to investigate geogrid–soil interaction. In the pullout tests on geogrids, either static or dynamic load is commonly used for applying the vertical loads. In order to investigate the influence of static and dynamic load on pullout test results, pullout tests are carried out to analyze the mechanical response of geogrids and soils under static and dynamic load from the large-scale pullout tester. The results show that frequency and amplitude have significant effects on the pullout test results under the dynamic load. The interface cohesion and friction coefficients under dynamic loads are smaller than those under static loads. The reinforcement effect of geogrids is reduced by dynamic load. Therefore, the strength of geogrids should be reduced when quasi-static analysis is used for reinforced structures. Knockdown factor is recommended for the corresponding reduction. The investigation results of this study may provide scientific references for regulating the design method of reinforced structures.

Effects of Geosynthetic Reinforcement on Tailings Accumulation Dams

Owing to the complexity of current reinforcement mechanisms, test results from existing models alone cannot provide a basis for the design of new tailings dam reinforcement projects. On-site reinforced tailings accumulation dam testing is thus required to further understand the reinforcement mechanism. In this study, the influence of reinforcement on tailings dams and the variation law of pore water pressure (PWP) and internal pressure (IP) in the dam body after slurry discharge were analysed, and a comparative analysis was performed. The results showed that during the field test, the PWP and internal earth pressure of the accumulation dam after grouting gradually increased over time. Reinforcement can greatly reduce the PWP and IP of the reinforced dam; compared with geotextiles, the reinforcement effect of geogrids is slightly greater. Based on these results, we conclude that geosynthetics are a good choice for strengthening tailings accumulation dams.