Effect Of Geosynthetic Reinforcement Research Articles

The effect of geosynthetic reinforcement on the load transfer mechanism of pile-supported low embankments subject to cyclic traffic loading

Pile-supported embankments are commonly employed for highways in soft soil areas. Extensive studies have been conducted on high embankments under static loading. However, low embankments with lower costs and carbon footprint have not yet been thoroughly studied. This study aims to investigate the performance of pile-supported low embankments under cyclic traffic loading by carrying out two large-scale model tests. The soft soil was constructed using Kaolin clay, and the cyclic traffic loading was simulated using a localized semi-sinusoidal function. The effect of geosynthetic reinforcement on the load transfer mechanism of pile-supported low embankments was investigated by comparing the measured data from unreinforced and reinforced cases. Test results show that geosynthetic reinforcement reduces settlement and leads to faster stabilization of settlement in low embankments. Pile-supported low embankments experience a rapid decrease followed by a stabilization in pile efficacy with increased cyclic loading, and geosynthetic reinforcement increase the pile efficacy and facilitate quicker stabilization. Geosynthetic reinforcement enhances the transfer of static and dynamic stresses to piles, resulting in less stress degradation under cyclic loading. Based on experimental results, pile-supported embankments should account for the adverse effects of cyclic loading, even if they are classified as high embankments according to existing analytical models.

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.

Influence of geosynthetic reinforcement on the progressive failure of rigid columns under an embankment load

Prior investigations have revealed that the stress characteristics of columns at different locations beneath an embankment vary. A failed column releases stress and causes significant increases in the stresses within neighbouring columns, possibly leading to progressive failure of adjacent columns and global failure of the embankment. Prior studies have presented insights into the progressive failure of column-supported embankments. However, limited insight has been provided into the progressive failure mechanism of geosynthetic-reinforced and rigid column-supported embankments. In this technical note, the effects of geosynthetic reinforcement on progressive failure are numerically analysed. A comparison of the progressive failure of rigid columns with and without geosynthetic reinforcement is first conducted. The restraining effects of geosynthetics on progressive failure of the columns and the influence of geosynthetic tensile stiffness on embankment stability are analysed. The results reveal that progressive failure is primarily governed by the distribution of the bending moment and the axial force within the columns. To further investigate the contribution of geosynthetics to resisting progressive failure of rigid columns, the internal forces in the columns and tensile strains in the geosynthetics are discussed.

Effect of geosynthetic reinforcement on the bearing capacity of strip footing on sandy soil

Due to the increasing presence of problematic soils, expansive clays and highly compressive sand engineers are using a verity of soil improvement techniques to treat such soils. While geosynthetics are extensively used for improving soil characteristics in roads, pavements and embankments, it can also be used to increase the lack of bearing capacity of residential housing or lightweight structures constructed on sandy soils. In order to simulate site conditions in the laboratory environment, a laboratory-scale testing platform has been manufactured to assess the behaviour of geosynthetics reinforced and un-reinforced strip footing. The first group of tests were performed on the unreinforced compacted sandy soils with different densities where the other group of tests were carried out in the soil that has been reinforced individually with three different types of geosynthetic materials having distinct tensile strengths. Furthermore, interface direct shear tests and consolidated undrained triaxial tests have been carried out to determine the shear parameters which is directly influencing the bearing capacity a strip footing. Geosynthetic reinforcement has considerably enhanced the mechanical behaviour of sandy soil in regarding the type of geosynthetic. Furthermore, it was observed that coir geosynthetic has provided increased interfacial friction when compared to other geosynthetic types and improved bearing capacity. Moreover, the adopted testing method found to represent well the behaviour of such materials in the laboratory environment.

Influence of Geosynthetic Reinforcement on Unpaved Roads Based on CBR, and Static and Dynamic Cone Penetration Tests

Dynamic cone penetrometer has been used widely as a pavement evaluation technique for many years. Unpaved roads constructed on weak soil subgrade are frequently subjected to severe damage and hence, they require regular maintenance and repair. One of the main stabilization methods of improvement of the serviceability of these roads is to reinforce them with geosynthetics (geotextile/geogrid). Field experiments were conducted on unpaved test sections reinforced with geotextile and geogrid, with the potential use of dynamic cone penetrometer (DCP) and digital static cone penetrometer (SCP) to assess benefits of geotextile and geogrid reinforcement. Laboratory California bearing ratio (CBR) tests were also conducted on subgrade–aggregate section and the effect of geosynthetic reinforcement was investigated by placing the reinforcement layer at the interface of the base course layer and weak subgrade. Digital SCP was used to measure the load–displacement behavior of geosynthetic-reinforced test section in the field. The field test results of DCP were expressed in terms of dynamic cone penetration index (DCPI, mm/blow), defined as the penetration depth of the cone per hammer blow and recorded along with the depth profile. A decrease in DCPI value was observed for the reinforced test sections as compared to the unreinforced test section. DCP results were able to detect transition zone and significant change in the strength of unpaved test section along with penetration depth. The field results indicate the greater resistance to penetration in the geosynthetic-reinforced test section and the penetrometer resistance increases with the depth. Higher penetration resistance offered by the geotextile has more contribution to the performance improvement of the test section.

Effect of Geosynthetic Reinforcement on Strength Behaviour of Weak Subgrade Soil

The performance of flexible pavement depends mainly on the subgrade soil characteristics as it serves as a foundation for pavement. Roads constructed over poor subgrade soil fails frequently leading to heavy economic burden apart from high initial cost of construction. In order to overcome these problems soil reinforcement technique has to be adopted. The use of geosynthetic material is a new and emerging technique and is gaining importance due to cost and time saving apart from less environmental sensitive nature. In the present study an attempt has been made to make use of non-woven geotextile and biaxial geogrid in various combinations. The geogrid was placed above geotextile, both in layers from the top of mold and heavy compaction, soaked CBR and unconfined compressive strength (UCS) tests were performed. Scanning electron microscopy (SEM) images indicate significant bonding between soil particles and geogrid surface.

Lateral Response and Failure Mechanisms of Rigid Piles in Soft Soils Under Geosynthetic-Reinforced Embankment

Previous studies regarding geosynthetic-reinforced pile-supported (GRPS) embankments over soft soils have mainly focused on load transfer mechanisms and design approaches. However, little attention was given to the lateral performance of rigid piles in GRPS embankment systems. This paper presents the results of 3D finite element analyses to examine and compare the lateral response and failure mechanisms of floating and end-bearing piles in soft soils under geosynthetic reinforced embankments. The effects of geosynthetic reinforcement and pile length on the stability of the embankments are also investigated. The results indicate that the induced lateral responses in the piles are distinctly different for floating and end-bearing piles. Failure of the floating pile is primarily caused by the inclination of the pile. However, for end-bearing piles, bending failure is clearly established as the principal mode of failure. The benefit of the geosynthetic layers in improving the stability of piled embankments is not particularly apparent. Moreover, the increase in pile length is significant in enhancing the stability of GRPS embankments. Specifically, when the normalized pile length varies from 0.75 to 1.15, the critical height of embankment increases from 6.2 to 11.8 m. However, the effect of pile length becomes negligible when the normalized pile length exceeds 1.15. The lateral movement and failure modes of GRPS embankments are strongly dependent on pile length. Therefore, it is essential to consider this aspect when analyzing the stability of the GRPS embankment.

Effect of geosynthetic reinforcement filled with aggregate on the bearing capacity of sand

ABSTRACT In this paper, numerical computations using FLAC code are carried out to investigate the effect of new construction technique combining substitution and reinforcement on the load-settlement of a strip footing on reinforced sand bed. The purpose is to examine numerically the improvement effect of using full wraparound ends of geosynthetic reinforcement for both cases: filled with the same founfation soil sand and filled with aggregate. A parametric study was carried out to investigate the effect of burial depth, width, tensile stiffness of reinforcement and on the effectiveness of the proposed full wraparound ends of reinforcement filled with aggregate. The results indicate that the proposed technique needs less quantity of reinforcement and aggregate than two planar reinforcements, requires a lower land space for creating a reinforced sand bed system and provides a significant improvement in the bearing capacity and stiffness of the sand bed. Abbreviatons Width of footing: B; b: width of the planar reinforcement; u: depth of the first planar reinforcement layers; h: vertical spacing between planar reinforcement layers; N: number of planar reinforcement layers; b': width of full wraparound ends of geosynthetic reinforcement; h': vertical of the full wraparound ends of geosynthetic reinforcement; u' depth of the full wraparound ends of geosynthetic reinforcement; BCR: bearing capacity ratio; BCRs: bearing capacity ratio at a settlement level s; qu: bearing capacity of footing on reinforced soil; S: settlement of the footing; EA: tensile stiffness of geosynthetic layers; φ: angle of internal friction; ψ: dilation angle; G: shear modulus of soil; K: bulk modulus of soil; γ: unit weight of soils

The Effects of Geosynthetic-Reinforcement on Consolidation Behavior of Soft Clay Embankment under Step Construction

Geosynthetics–reinforced structures are widely used in embankments and walls. This paper presents the simulation of the embankment under load in order to compare the behavior of clay embankment with and without wrapping-facing-geosynthetics-reinforcement using finite element method (FEM) and to analyse the variation of behavior included of displacement and excess pore pressure under the different over-consolidation ratios (OCR). The calculation results show that embankment with higher OCR showing lower displacement compare to embankment with lower OCR. However, OCR isn’t very sensitive to the dissipation of excess pore pressure. Geosynthetics-reinforcements could reduce the displacement of embankment and accelerate dissipation of excess pore pressure after construction and surcharge. Gravel, geosynthetics-reinforcement and clay soil are properly combined, clayey soil is expected to be useful as embankment material.

Investigating the performance of geosynthetic-reinforced asphaltic pavement under various axle loads using finite-element method

One of the major factors influencing the performance of highway pavements is traffic loading, which is continuously increasing in number, magnitude and contact pressure. Geosynthetic reinforcement of asphalt pavements is a method for improving the bearing capacity of pavements against heavy traffic loads. This study aims to investigate the effectiveness of geosynthetic on the reduction of critical strains of flexible pavements under various axle load levels. Three types of geogrid have been placed in different positions in a typical asphalt pavement structure, and the critical strains, including the compressive vertical strain on top of subgrade, the maximum tensile strain at the bottom and the maximum shear strain of asphaltic layer have been evaluated under different axle loads of 5, 8.2 and 15 ton. The finite-element method has been utilised for modelling and analysis of pavement structure, in which, the asphaltic layer has been characterised as a viscoelastic material using Prony series. Results show that placing the geosynthetic beneath the asphaltic layer results in the reduction of the longitudinal tensile strain of asphaltic layer, while it is not effective on the vertical compressive strain on the subgrade. Furthermore, results show that, in spite of increasing the critical strains with increasing axle load, the effectiveness of geosynthetic reinforcement under different axle loads varied. At higher levels of axle load, the geosynthetic on the subgrade is more effective in reducing the compressive strain on the subgrade. However, the effectiveness of the geosynthetic beneath the asphaltic surface layer decreases with increasing axle load. In addition, the highest improvement in the effectiveness of geosynthetic for reducing the critical strains at higher axle load levels is achieved when it is placed at the position of the desired critical strain. It is also found that the effectiveness of geosynthetic in reducing the critical strains at higher axle loads increases with an increase in the modulus of geosynthetic.

Three-dimensional finite element modelling of a full-scale geosynthetic-reinforced, pile-supported embankment

The performance of four sections of a full-scale embankment constructed on soft soil is examined using a fully coupled and fully three-dimensional finite element analysis. The four sections had similar embankment loadings but different improvement options (one unimproved, one with pile-support only, one with a single layer geotextile-reinforced platform and pile-support, and one with two layers of geogrid-reinforced platform and pile-support). Like the field data, the numerical results show that the inclusion of piles decreases the settlement at the subsoil surface to 52% of that for the unimproved section, and the addition of a single layer of geotextile reinforcement (J = 800 kN/m) further reduced settlement to only 31% of that of the unimproved section. The effects of geosynthetic reinforcement and multiple layers of reinforcement on the performance of the pile-supported embankment are discussed. The relative load transfer is calculated using eight existing methods and they are compared with the field measurements and numerical results.

Long-Term Evaluation of Geosynthetic Reinforcement of Flexible Pavements Constructed over Thick Organic Soil Deposits

Many regions throughout Florida have thick deposits of organic soil. Roadways built over these deposits often exhibit differential settlement, significant rut depths, and extensive cracks in a relatively short period of time. The Florida Department of Transportation constructed an experimental project on a realigned portion of State Road 15 on the southeastern shore of Lake Okeechobee in Palm Beach County to evaluate the effect of geosynthetic reinforcement on pavement performance. This roadway traverses farmlands with deep layers of organic material just beneath the surface and has a history of poor performance. The experimental project included four 500-ft sections with combinations of geogrids and geotextiles placed below the base and above the organic material. A fifth section of similar length was constructed with no geosynthetic reinforcement and served as a control. In addition to geosynthetic reinforcement, the alignment was surcharged before construction. The investigation showed that surcharging alone significantly improved the pavement performance compared with historical pavement condition and rehabilitation records. Geosynthetic reinforcement doubled the equivalent single-axle loads allowed on the unreinforced section. A rigid geogrid or woven geotextile placed below the base appeared to provide a slightly stiffer and better-performing pavement than a flexible geogrid. This paper documents the research program and provides details on the improvement resulting from surcharging and geosynthetic reinforcement.

Effect of Geosynthetic Reinforcement in Active Zone on the Behavior of Sheet Pile Walls

The potential benefits of reinforcing the active zone behind a model sheet pile wall were studied. A series of plane strain laboratory model tests were performed on both unreinforced and reinforced active zones loaded with a rigid strip footing. Parameters including the sand relative density, reinforcement embedment depth, type of reinforcement, footing location relative to the sheet pile wall, length of reinforcement, and number of reinforcing layers were varied. The sheet pile wall deflection during loading was measured. Finite element (FE) analyses were performed on a prototype sheet pile wall to supplement the results of the model tests. A two-dimensional plane strain FE model using the computer code PLAXIS was used. Close agreement between the experimental and numerical results was observed (about 4 % to 11 %). The results indicate that the inclusion of reinforcement in the active zone leads to a reduction by about 48 % to 75 % in the lateral deflection. The effectiveness of the reinforcement in decreasing the lateral deflection of the sheet pile wall is attributed to its tensile strength and type. Based on the results of the laboratory model and the numerical analyses, critical values of reinforcement parameters for maximum reinforcing effects are suggested. The results are used to development linear regression equations relating the ultimate lateral capacity of the sheet pile wall to the aforementioned parameters.

An experimental evaluation of the behavior of footings on geosynthetic-reinforced sand

This research was performed to investigate the behavior of geosynthetic-reinforced sandy soil foundations and to study the effect of different parameters contributing to their performance using laboratory model tests. The parameters investigated in this study included top layer spacing, number of reinforcement layers, vertical spacing between layers, tensile modulus and type of geosynthetic reinforcement, embedment depth, and shape of footing. The effect of geosynthetic reinforcement on the vertical stress distribution in the sand and the strain distribution along the reinforcement were also investigated. The test results demonstrated the potential benefit of using geosynthetic-reinforced sand foundations. The test results also showed that the reinforcement configuration/layout has a very significant effect on the behavior of reinforced sand foundation. With two or more layers of reinforcement, the settlement can be reduced by 20% at all footing pressure levels. Sand reinforced by the composite of geogrid and geotextile performed better than those reinforced by geogrid or geotextile alone. The inclusion of reinforcement can redistribute the applied footing load to a more uniform pattern, hence reducing the stress concentration, which will result reduced settlement. Finally, the results of model tests were compared with the analytical solution developed by the authors in previous studies; and the analytical solution gave a good predication of the experimental results of footing on geosynthetic reinforced sand.

The effectiveness of geosynthetic reinforcement, tamping, and stoneblowing of railtrack ballast beds under dynamic loading: DEM analysis

Discrete Element Method (DEM) simulations were developed to investigate the effectiveness of geosynthetic reinforcement and the effectiveness of maintenance techniques performed on a simulated ballast bed subjected to dynamic loading. The results from four samples subjected each one to a total of 425 load cycles are presented: one unreinforced and unmaintained sample, one unmaintained but reinforced sample, one unreinforced sample subjected to maintenance in the form of stoneblowing after 200 load cycles, and one unreinforced sample subjected to maintenance in the form of tamping after 200 load cycles. The obtained values of permanent deformation as a function of the applied number of load cycles for the four cases are presented together allowing a comparison of the effectiveness of each technique. Moreover, snapshots of the simulated track sections are presented at different moments of the simulations. The simulations indicated that the geosynthetic reinforcement may not be beneficial for the analyzed case while stoneblowing was the most effective maintenance technique.

Axi-symmetric Analysis of Geosynthetic-reinforced Granular Fill-soft Soil System with Group of Stone Columns

The paper presents a mechanical model to predict the behavior of geosynthetic-reinforced granular fill resting over soft soil improved with group of stone columns subjected to circular or axi-symmetric loading. The saturated soft soil has been idealized by spring-dashpot system. Pasternak shear layer and rough elastic membrane represent the granular fill and geosynthetic reinforcement layer, respectively. The stone columns are idealized by stiffer springs. The nonlinear behavior of granular fill and soft soil is considered. Consolidation of the soft soil due to inclusion of stone columns has also been included in the model. The results obtained by using the present model when compared with the reported results obtained from laboratory model tests shows very good agreement. The effectiveness of geosynthetic reinforcement to reduce the maximum and differential settlement and transfer the stress from soft soil to stone columns is highlighted. It is observed that the reduction of settlement and stress transfer process are greatly influenced by stiffness and spacing of the stone columns. It has been further observed that for both geosynthetic-reinforced and unreinforced cases, the maximum settlement does not change if the ratio between spacing and diameter of stone columns is greater than 4.