Geocell Height Research Articles

Parameters affecting performance of fully instrumented model testing of strip footings on geocell-reinforced soils

A thorough study was conducted to assess the performance of the strip footing reinforced with geocells in sand, focusing on understanding the enhancement effects and geocell reinforcement mechanisms. Critical factors such as geocell modulus, height, soil relative density and load eccentricity were examined through fully instrumented model tests. Measurements included surface displacement profiles, strains on the geocell layer, subsurface pressure distribution and other relevant parameters. Results revealed that the strip footing on geocell-reinforced sand beds exhibited better performance compared to those on unreinforced soil, characterized by increased load-carrying capacity and reduced settlements. Notably, stiffer geocells improved performance significantly, with a 40% higher modulus enhancing the bearing pressure by up to 25%, due to better confinement and anchorage effects. Conversely, geocells with a lower modulus demonstrated more effective vertical stress distribution. Furthermore, increased geocell height moderately enhanced footing performance by improving confinement, although wall buckling under eccentric loading limited major gains. Dense soils under centric loading exhibited up to a 20% better improvement in bearing pressure than loose soils due to higher strain mobilization within the geocell layer. These findings highlight the crucial role of geocell and soil properties, as well as loading conditions, in optimizing reinforcement effects for strip footings.

Experimental investigation of the geometry of geocell on the performance of flexible pavement under repeated loading

To evaluate the benefit of geocells of different geometrical configurations for pavement application, full-scale instrumented model tests were performed on pavement sections reinforced with geocells of different geometrical configurations subjected to monotonic and repeated loading. The responses studied were stress distribution in different pavement layers, induced strains in geocell walls, and settlement characteristics. The reinforced sections exhibited a significant reduction in rut depth as well as localized stress concentration compared to the unreinforced section. The reduction in rut depth was found to be influenced by the geocell height as well as weld spacing. The geocell reinforcement was found to distribute the stresses in the subgrade and subbase layers more efficiently, thus reducing the stress concentration in these layers. The strain measurements were found to be higher at the bottom of the geocell walls indicating a higher confinement effect on a lower part of the geocell. In the field, mostly geocells of 356 mm weld spacing and 150 mm height (SW356-H150) are used. However, this study suggests that a geocell of 330 mm weld spacing and 100 mm height (SW330-H100) having approximately 30% lower cost compared to SW356-H150 is as effective in reducing the rut depth and localized vertical stress distribution.

Performance of eccentrically loaded strip footings on geocell-reinforced soil

In this pioneering study, the performance of an eccentrically loaded strip footing on geocell-reinforced sand was assessed with instrumented laboratory model tests in terms of pressure-settlement response, surface displacement profiles, failure mechanisms and ultimate bearing capacity considering load eccentricity, geocell height, geocell material stiffness and the relative density of the soil. The results indicated that strip footings on the geocell-reinforced sand outperformed those on unreinforced soils, with up to a 6.5-fold increase in the bearing capacity and significant improvements in the initial slope of the pressure-settlement curve. Furthermore, the strip footing under centric loading on the geocell-reinforced loose and dense sand exhibited either only punching or local shear failure while load eccentricity on the strip footing could lead to the shear failures including punching, local and general. In this research, both a design chart for predicting failure modes of geocell-reinforced strip footings and a new interpretation method to evaluate ultimate bearing capacity were proposed. Increasing the relative density of the soil and material stiffness enhanced the ultimate bearing capacity of geocell-reinforced strip footings under both centric and eccentric loading conditions, with stiffer materials resulting up to 25% increase. However, increased geocell height had no significant impact on bearing capacity.

The effect of the geometrical properties of geocell reinforcements between a two-layered road structure under overload conditions

Depending on the project traffic, the total thickness of a granular base can reach excessive values. Granular layers of large thicknesses undoubtedly extend the duration of a project and cause high project total costs. In this study, the improvement in settlement behaviour of unbound granular base layers reinforced with geocell was investigated by way of large-scale laboratory tests and finite element modeling. Plate loading tests were performed on unreinforced and geocell reinforced base layers, which were constructed on subgrade soil with a low bearing capacity under 1750 kPa overload condition. It was determined that the amount of settlement observed at the same stress levels decreased with an increase in the aperture size from 440 mm to 660 mm and the geocell height from 100 mm to 150 mm. The reduction in settlement potential, which reached 78% compared to the unreinforced reference section around 25 kPa, decreased to 55% at around a 200 kPa standard load. With an increase in the vertical stress level, the effectiveness of geocell reinforcement decreases and a serious decrease occurs after 500 kPa, becoming completely unserviceable when a level of 1000 kPa is to be exceeded. Although the difference between the experimental results and the modeling values remained below 5% in the reference section, it reached as high as 30% differences in the geocell implemented sections up to 200 kPa, due to three-dimensional geocell adaptation problems within the finite element calculations. In this way, it will be possible to increase the performance of road surfaces by keeping the pavement thickness constant, and also it will be possible to design more economical sections by reducing the required thickness.

Dynamic stress attenuation characteristics of geocell-reinforced railway subgrade

The dynamic stresses in many subgrades for old railways exceed the bearing capacity of the fillers. The geocell has been used to reinforce weak subgrades and achieve a quick attenuation in the dynamic stress. In this study, a series of field tests were conducted to investigate the dynamic stress attenuation characteristics in a weak subgrade reinforced with a geocell. A coupled finite element-discrete element model was developed to analyze the mechanism of the stress attenuation from a multiscale perspective. The results indicated that increasing the geocell height or decreasing the weld distance resulted in an increase in the attenuation rate. There was a threshold for the weld distance, below which its impact on the stress attenuation rate became negligible. When the weld distance was small, the dynamic stress attenuation was attributed to the geocell induced lateral confinement for the infilled soil. With the weld distance increasing, the deformation of the geocell increased and the membrane effect was further mobilized, which contributed to the dynamic stress attenuation. Based on the field test and numerical results, a design method was proposed to determine the reinforcement parameters of geocell-reinforced subgrade, aimed at improving dynamic stress attenuation and preventing subgrade distress.

Performance and Application of Geocell Reinforced Sand Embankment under Static and Cyclic Loading

As reinforcement material, geocells are widely used in various types of embankment reinforcement. A lot of practical experience shows that geocell reinforced embankment has good reinforcement effect, but the theoretical research lags behind the engineering practice, and the reinforcement mechanism under cyclic loading under various reinforcement conditions needs to be further studied. In this paper, the reasonable reinforcement condition of geocell reinforced embankment under static and cyclic loading is proposed by using a physical model and numerical simulation comparative analysis method. The research findings include: under cyclic loading, the inhibition effect of the number of reinforced layers on the vertical cumulative settlement is better than that under static loading, but the effect of two-layer reinforcement and three-layer reinforcement is relatively close, and both can reduce the vertical settlement by more than 40%. The inhibition effect of the increase of geocell height on the horizontal deformation of slope surface is better than that of the decrease of welding spacing under cyclic loading, and the reinforcement effect of the middle and upper part of embankment is better. Increasing the height of geocell and reducing the welding spacing can improve the limit bearing capacity of embankment, and the former is better. The optimal reinforcement condition of sandy soil embankment under cyclic loading obtained from the comparative analysis is case 3, that is, the reinforced layers is 2, the geocell height is 10 mm, and the welding distance is 50 mm.

Internal stability analysis of geocell-reinforced slopes subjected to seismic loading based on pseudo-static approach

Seismic stability analysis of geocell-reinforced slopes (GRSs), considering shear and moment strength in addition to tensile resistance for geocells, is a novel topic for which scarce studies are found in the literature. Despite few available studies, an analytical approach is presented in this study to investigate the seismic internal stability of GRSs, employing the pseudo-static method based on a limit state approach. Results are given in terms of conventional design charts representing the required total strength and critical length of geocells. The results show that with increasing the horizontal seismic acceleration (kh), the internal stability degenerates since the required strength and critical length of geocells increase. For GRSs subjected to greater kh, the effect of increasing the vertical seismic component (kv) on increasing the required strength and length of geocells is more considerable than those subjected to lower kh values. Parametric analyses are conducted, under various seismic conditions, to investigate the effect of increasing the geocell height and raising the number of geocell layers, leading to the reduction in the required strength and length of geocells. Such effects are found to be dependent on the parameters such as the intensity of seismic excitation, material properties and geometry of slope.

Assessment of load distribution mechanism in geocell reinforced foundation beds using Digital Imaging Correlation Techniques

The pressure distribution below geocell reinforced foundation beds depends on several factors like height of geocell, weld distance (pocket size), infill material, etc. This paper describes a method to determine the load dispersion mechanism through a geocell layer using a non-contact Digital Image Correlation technique. Series of plate load tests were performed in a test tank having plan dimensions of 0.6 m × 0.6 m and height of 0.65 m. The loading was applied through a strip footing of width 120 mm. Two miniature geocells having heights of 60 mm and 75 mm were used for reinforcing the base layer of the foundation section. The studies were performed with two types of geocells having smooth and rough surfaces. The relative density (RD) of the base and subgrade layers were maintained as 80% and 40%, respectively during the tests. The movement of soil particles was recorded by capturing images at different stages of the test. The images were processed using a Digital Image Correlation (DIC) software to obtain displacement contours and vectors. The results show that the geocells distribute the load over a wide area of the foundation soil. The dispersion angle was found to depend on the height of geocell and the roughness of the geocell surface. The load dispersion angles obtained from Digital Image Correlation analyses of unreinforced and reinforced sections have been compared with similar published results.

The Effects of Geocell Height and Lime Stabilization on Unpaved Road Settlements at Different Water Contents

In this study, lime stabilization and geocell reinforcement methods were investigated for a clayey subgrade of unpaved road at different water contents. This study is especially important in terms of determining the soil improvement method for road construction on wet lands. The effects of the geocell height (50, 100, 150, and 200 mm) and lime content (3, 6, and 12%) on the settlement of the subgrade soil at different water contents (25, 28, 30, 32, and 35%) were analyzed. Accordingly, a large scale plate loading test was designed, and it is utilized to achieve loading-settlement curves. The bearing capacity and modulus of subgrade (k) of soil were determined. It was detected that the geocell height and lime content have different effects at different water contents, and the modulus of subgrade reaction became stable beyond a constant height of the geocell. It was understood that none of these two improvements did not meet the Highways Technical Specifications. It is detected that at least these two improvement techniques are needed to be applied together to meet the specifications for the soil examined in this study.

Laboratory and Numerical Studies on the Performance of Geocell Reinforced Base Layer Overlying Soft Subgrade

The use of geocells for support of foundations on weak subgrades has been gaining popularity in recent years. Detailed studies were performed in this work through laboratory tests and numerical simulations to investigate the influence of different parameters on the geocell supported foundations on soft subgrades. A series of large-scale laboratory plate load tests were performed on the geocell-reinforced base layer overlying soft subgrade. The soft foundation soil was simulated using blocks of Expanded Polystyrene (EPS) in the laboratory tests for obtaining consistent subgrade conditions between the tests. The numerical analyses were performed in three-dimensional finite difference numerical program Fast Lagrangian Analysis of Continua in Three Dimensions (FLAC3D). The numerical models were calibrated against the data obtained from laboratory tests. This paper deals with investigating the influence of different parameters such as pocket opening size, height and size of the footing on the performance of geocell-reinforced base layer overlying soft subgrade. The provision of three-dimensional cellular reinforcement (geocells) in the base layer has substantially increased the bearing capacity of the pavement section and the optimum aspect ratio of geocell pocket was found to be close to unity. From the parametric study, it is observed that the potential benefits of geocell reinforcement increases with reduction in weld spacing and height of geocell while the influence decreases with increasing loading area for constant height of geocell layer.

Static stability analysis of geocell-reinforced slopes

This paper presents an analytical approach to investigate the stability of geocell-reinforced slopes using the limit equilibrium method (LEM). The so-called Horizontal Slice Method (HSM) is employed to simulate horizontal geocell layers. Each geocell layer acts as a beam providing bending and shear resistance in addition to axial strength. A formula is devised by picking relevant governing equilibrium equations, fitted to the new concept employed exclusively for analysis of geocell-reinforced slopes. Parametric studies are conducted to evaluate the effects of increasing the geocell height and replacing geogrids by geocells with various heights for slopes with different characteristics. The results showed that such actions would reasonably reduce the required tension and length of the reinforcement layers, meaning that the stability condition is improved and the less lengthy reinforcement system is formed. Output values also showed dependency on the slope angle and its material properties.

Experimental Investigation on the Reuse of Reclaimed Asphalt Pavement over Weak Subgrade

Reclaimed asphalt pavement (RAP) materials are a sustainable solution for highway construction and therefore gained more attention in recent years. The bearing capacity of RAP is not sufficient to withstand the applied wheel loads, resulting in excessive deformation and vertical stresses. The geosynthetic reinforcement improves the load-bearing capacity of RAP bases and makes pavement usable for traffic. This paper presents the experimental results of static plate load test on unreinforced and geocell-reinforced bases; furthermore, the geotextile functioning was also observed. The surface deformation decreases with the increase in the height of geocell and placement of geotextile. The geocell restricts the lateral movement by increasing the lateral resistance of infill material; geotextile at the interface decreases the deformation and vertical stress transferred to the weak subgrade. The geocell of different heights (10 cm, 12.5 cm and 15 cm) was used in this study with varying thicknesses of base course. The geocell and geotextile reinforcement increases the bearing capacity by 43%, 88% and 96% in the case of 12-cm-, 15-cm- and 20-cm-thick bases respectively. The average vertical stress decreases by 53% and the stress distribution angle increases from 21 to 60°. The overall findings showed that the geosynthetics improved the performance of RAP bases, making them reusable for pavement construction.

Undrained triaxial compression tests on three-dimensional reinforced sand: effect of the geocell height

This paper presents an experimental thorough study on geocell reinforced loose sand (Dr = 25%), focusing on the improvement of the shear strength in undrained conditions. The experimental program includes a series of undrained compressive tests (CU) performed on loose sand samples with and without reinforcement. The experimental tests are performed for various geocell height (Hg = 15, 25 and 35 mm) and at different level of effective confining pressure (σ’c = 50, 100 and 200 kPa). The obtained results show a significant effect of geocells height and initial confining pressure on the shear strength of the reinforced sand. The apparent cohesion of the reinforced soil increases linearly with the axial strain while the friction angle is rather constant and slightly dependent on the sample deformation.

Uplift behavior of shallow horizontal plate anchors reinforced with geocells in cohesionless soil

Reduced scale laboratory tests were conducted to assess effects of anchor embedment ratio (), geocell width ratio (), geocell height ratio () and geometrical shapes of anchors on uplift behavior shallow horizontal plate anchors reinforced with/without geocell material in cohesionless soil. It was determined that the effects of geometrical shapes of anchors having equivalent surface area on the uplift behavior of plate anchors with/without geocell reinforcement were negligible. An increase in the and of geocell yields to an increase in both the uplift capacity and the residual capacity of anchor of shallow horizontal plate anchors while heave on the soil surface spreads to larger area. The effectiveness of geocell reinforcement was evaluated in terms of improved ratio () varying from 1.04 to 6.01 at given values of anchor displacement ratio (S/B), and Simply, optimum geocell width ratio ( of 2.4 was obtained. Additionally, failure surface and dispersion angle of anchors obtained via the help of miniature laboratory test were compared with the results of the reduced scale laboratory test. Finally, a theoretical approach was established to predict the uplift capacity of shallow horizontal plate anchors reinforced with/without geocell in cohesionless soil.

Performance Assessment of Square Footing on Jute Geocell-Reinforced Sand

Incorporation of three-dimensional geocell is a soil reinforcement technique which is extensively used today and has proved to be reliable due to its confining capability which increases the load-carrying capacity of the soil. The concern over the deterioration of soil and the escalating costs of the presently used synthetic geocells has steered the need for a natural replacement. This research provides a precis of the sand bed being reinforced with jute geocell, developed with jute geotextile and its effectiveness evaluated through model plate load tests in the laboratory using a square footing. The parameters administering the performance, such as the depth of sand cushion above geocell (u), width of geocell (b), and height of geocell (h) with respect to the width of the footing (B) are varied to realize the optimum of the ratios. The results obtained from the test conducted to optimize the ratios are scrutinized to study the improvement in bearing capacity of soil. The bearing pressure of the jute geocell-reinforced soil at 10% settlement is 3.5 times higher than that of the unreinforced soil. The inherent properties of natural fibres like jute can meet the requirement of synthetic geocells and their eco-compatibility make them to rule over existing geocells. According to the procured results and discussion through the study, it is proven that jute geocells could very well be an alternative for reinforcing the soil.

Vibration isolation using 3D cellular confinement system: A numerical investigation

This paper investigates numerically the potential use of cellular confinement systems in isolating the machine induced vibrations. The numerical analysis was carried out using the three dimensional explicit finite difference package FLAC3D. Primarily, the numerical model was validated with the results of field resonance tests, performed on the foundation beds reinforced with and without cellular confinement systems. The 3D cellular confinement was simulated using two techniques, namely, Equivalent Composite Approach (ECA), and Honeycomb Shape Approach (HSA). The isolation efficiency of the confined cell was determined in terms of the reduction in displacement amplitude, peak particle velocity, and the improvement in elasticity of the foundation bed. From the results, 56% reduction in displacement amplitude was observed in the presence of geocell reinforcement. Similarly, 42% change of resonant frequency was observed as compared to the unreinforced condition. The elasticity of the foundation bed was improved by 102% with the provisions of geocell. Further, it was noticed that the modelling of geocell through the HSA approach provided the accurate prediction of the experimental results. With the help of HSA technique, the effect of confinement area and the height of geocell in reducing the amplitude of vibration was investigated. Further, the parametric study was conducted to investigate the effect of different geocell properties on the dynamic behaviour of reinforced foundation bed. The parametric study results revealed that the geocell modulus and the interface friction angle directly influence the performance of geocell reinforced bed under dynamic loading condition.

Three-dimensional numerical modelling of geocell reinforced soils and its practical application

This paper proposes a new numerical approach to model geocell reinforced soils, where the geocell is described as membrane elements and the complex interaction between geocell and soil is realized by coupling their degrees of freedom. The effectiveness and robustness of this approach are demonstrated using two examples, i.e., a geocell-reinforced foundation and a large scale retaining wall project. The first example validates the approach against established solutions through a comprehensive parametrical study to understand the influence of geocell on the improvement of bearing capacity of foundations. The study results show that reducing the geocell pocket size has a strong effect on improving the bearing capacity. In addition, when the aspect ratio maintains the same value, the bearing capacity improvement with increasing geocell height is insignificant. Comparing with the field monitoring and measurement in the project, the second example investigates the application of the approach to practical engineering projects. This paper provides a practically feasible and efficient modelling approach, where no explicit interface or contact is required. This allows geocell reinforced soils in large scale project can be effectively modelled where the mechanism for complex geocell-soil interaction can be explicitly observed.

Predicting the Settlement of Raft Resting on Sand Reinforced with Planar and Geocell Using Generalized Regression Neural Networks (GRNN) and Back Propagated Neural Networks (BPNN)

In this study, geogrid and geocell as soil improvement methodologies had been used to improve the tensile characteristics of soil. The variation in settlement by using geogrid as reinforcing material at different relative density, different combination of reinforcement depths with different layers of reinforcement of soil with geogrid had been studied by conducting lab experiments. The results of the various experiments have been modeled using back propagated neural networks (BPNN) and generalized regression neural networks (GRNN) for predicting settlements at different combinations of placing of geogrid in soil. Both the models had been compared and it was found that in case of geogrid as a reinforcing material BPNN model with Levenberg–Marquardt algorithm gave better results compared to GRNN models. The results of experiments with geocell as a reinforcing material were also used separately with variable parameters such as relative density, depth of reinforcement, number of layers, and height of geocell for making BPNN and GRNN models.

Evaluating the performance of geocells made from needle-punched nonwoven layers in the bearing capacity of reinforced soil

This study focuses on the investigation of the effect of constituent elements of geotextile layers on the bearing capacity of geocell-reinforced soil. For this purpose, geocells with different geometries were prepared using polyester nonwoven layers formed by fibers with various cross sections. Series of reduced-scale laboratory model tests were carried out to determine the bearing capacity of footing supported by geocell reinforced soil. The results showed that the bearing capacity of soil increases substantially by provision of geocell. Furthermore, greater improvement in the performance of geocell is observed by increasing the geocell height and decreasing the pocket dimensions. It is also concluded that layers made from blend of fibers with different cross sections improve the bearing capacity of reinforced soil more than those of uniform cross section.

Influence of geocell reinforcement on uplift response of belled piles

Piles are frequently used to transfer the heavy compressive loads to strong soil layers located in the depth of bed. In addition, such piles may be subjected to combination of repeated compressive and tensile loads due to earthquake, wind, etc. This paper describes a series of laboratory model tests, at unit gravity, performed on belled pile, embedded in unreinforced and geocell-reinforced beds. The tests were performed to evaluate the beneficial effect of geocell in decreasing the downward and upward displacements and performance improvement of the uplift response of belled pile under repeated compressive and tensile loads. Pile displacements due to fifty load repetitions were recorded. The influence of the height of geocell above the bell of pile, an additional geocell layer at the base of belled pile, and the number of load cycles on pile displacements were investigated. The test results show that the geocell reinforcement reduces the magnitude of the final upward displacement. It also acts as a displacement retardant, and changes the behaviour of belled pile from unstable response condition due to excessive upward pile displacement in unreinforced bed to approximately steady response condition. Therefore, the geocell reinforcement permits higher tensile loads or increased cycling. The efficiency of reinforcement in reducing the maximum upward displacement of the pile (i.e. pull-out resistance) was increased by increasing the height of geocell above the bell of the pile. Furthermore, the comparison showed that a specific improvement in upward and downward displacement and the stability against uplift can be achieved using an additional geocell layer at the base. The geocell reinforcement may reduce the required length of pile shaft, consequently reducing required excavation, backfill, and pile’s material. Simple dimensional analysis showed the need for an increased stiffness of the geosynthetic components in order to match prototype-scale performance similitude.