Number Of Geogrid Layers Research Articles

Geogrid reinforcement for improving bearing capacity and stability of square foundations

Abstract Shallow foundations are often the most economical option for building support, as they distribute structural weight to soil layers, require minimal earthwork, and do not necessitate specialized machinery. The most common type of soil in the city of Karbala is sandy soil. It is granular and loose by nature which has a relatively low bearing capacity. According to previous studies, the soil weakness is one of the problems with shallow foundation construction. Thus, the aim of this study is to improve the properties of the soil using geogrid reinforcement. Three critical parameters are examined, including depth, size, and number of geogrid layers in the soil reinforcement process to increase bearing capacity and decrease soil settling. The effect of geogrid depth (u) was studied by considering four depth ratios (u/B = 0.5, 1.0, 1.5, and 2.0) in order to determine the ideal depth of the geogrid layer, where (B) refers to the width of the footings. The results indicated that a decrease in depth ratio significantly increased the bearing capacity of footings built on reinforced soil layers compared to those built on natural soil, and the settlement reduction ratio (SRR) also increased. The size of the geogrid layer (i.e., width of the geogrid layer (b) was evaluated by evaluating four size ratios (b/B = 1.5, 3.0, 4.5, and 6.0). With an increasing size ratio of the geogrid layer, the bearing capacity ratio (BRC) was significantly improved. Additionally, the study examined the optimal number of geogrid layers, focusing on single and multiple layers with N = 1, 2, 3, and 4. The results showed a higher BRC for footings on reinforced soil layers, as well as a significant rise in SRR with an increase in the number of geogrid layers. Finally, it was concluded that the optimal depth ratio was u/B = 0.5, the size ratio was b/B = 4.5, and reinforced with three geogrid layers, which provided the highest bearing capacity and SRR. The experimental test results were verified by comparing them with those calculated using theoretically developed models. The variation between the experimental and theoretical results is reasonable, confirming that the experimental testing results exhibit a high degree of accuracy.

Performance of a triaxial geogrid-reinforced crushed rock base underlain by a soft clay subgrade

This large-scale test investigated the behavior of a pavement structure composed of a crushed rock base underlain by a soft clay subgrade reinforced with a triaxial geogrid under static loading. The fully instrumented pavement model included a 0.8-m-thick soft clay layer and a 0.2-m-thick crushed rock layer. A triaxial geogrid, Triax TX150, was installed at the interface between the subgrade and base layers and the mid-depth of the crushed rock base. Both unreinforced and reinforced pavement models were prepared in a square steel mold of 1.5 m width and 1.2 m height. Plate load tests were conducted according to ASTM standards. The results revealed that the number of geogrid layers and their locations influenced the reinforced pavement’s ultimate bearing capacity and failure mechanisms. Two-layer reinforcement (between the crushed rock and soft clay layers and in the middle of the crushed rock layer) provided the maximum bearing capacity, with an improvement factor of 1.63 compared to that of the unreinforced pavement, because the triaxial geogrids changed the failure mode of the unreinforced pavement from punching failure in the crushed rock and local shear failure in the soft clay to only punching failure in the crushed rock. Thus, triaxial geogrids are suggested for enhancing the performance of pavements on soft clay subgrades.

Influence of Geogrid on the Flexural Behavior of Cracked Concrete Pavements

This paper investigates the influence of geogrid reinforcement on the flexural behavior of concrete pavements after the initiation of cracks up to failure. Two groups of notched concrete beam specimens with the dimensions of 150 mm × 150 mm × 550 mm were tested. The concrete specimens of the first group were tested under static loads. The concrete specimens of the second group were tested under cyclic loads. The geogrid was placed at a depth of 55 mm from the bottom of the concrete specimens. Test results illustrate that, when cracks are visible in the concrete specimens, the geogrid could maintain the flexural behavior of the concrete pavements within the acceptable service level. The geogrid significantly prolonged the fatigue life of the cracked concrete pavements reinforced with the geogrid. The geogrid increased the maximum cyclic loads of the concrete specimens reinforced with geogrid before eventually failing. The number of geogrid layers used as a flexural resisting material under cyclic loads acts a significant role in improving the behavior of the concrete pavements compared with the specimens reinforced with one layer of geogrid.

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.

Behavior of Square Footings Reinforced with Glass Fiber Bristles and Biaxial Geogrid

This study investigates the influence of biaxial geogrids on the flexural behavior of square footing foundations reinforced with glass fiber reinforced concrete (GFRC). Experimental research is conducted, involving the testing of five reinforced concrete square footings under area loading until failure. The variables considered are the number of geogrid layers and the percentage of longitudinal reinforcement. Various parameters including deflection, loads at each stage, stiffness, ductility, energy absorption, crack patterns, as well as strains in steel, concrete, and geogrid, are analyzed and compared. The results reveal that incorporating geogrid layers as a reinforcement technique with GFRC significantly enhances the flexural behavior of the footings and improves cracking patterns. The number of geogrid layers used in the footings substantially increases the loads at each stage. Furthermore, an empirical equation is developed to establish a correlation between the moment acting on the footings and the tensile strength of geogrid reinforcement. The empirical evidence demonstrates a substantial improvement in the strength resistance of geogrid-reinforced footings with GFRC, surpassing those reinforced with steel and normal concrete mix. This research contributes valuable insights for the design and construction of earth structures, highlighting the advantages of biaxial geogrids in reinforcing GFRC footings with enhanced flexural performance.

Performance of loosely skirted square footing resting on reinforced sand under vertical concentric and eccentric loading

ABSTRACT The present study investigates the performance of loosely skirted square footing resting on multi-layered geo-grid reinforced medium dense sand under vertical concentric and eccentric loading through a series of laboratory model tests. The load eccentricity (e) is varied as 0, 0.1B, 0.15B, 0.2B (where B is the width of the footing). Parametric variations like depth of skirt (d = 1B, 1.5B, 2B), number of geo-grid layers (N; varies with variation of depth of skirt), spacing between horizontal reinforcements (Y = 0.25B,0.5B,0.75B,1B) have been investigated with a constant surface dimension D/B = 1(D is the top surface dimension of the skirt). The test results show that load intensity increases significantly with the increment of skirt depth and approaches the optimum value at d/B = 2 for a spacing of 0.25B for both the loading conditions. However this increment is less prominent for footing with only skirt and without reinforcements. Increment in number of horizontal reinforcements too showed an increase in bearing capacity and reduction in settlement. Effect of eccentricity on load intensity for both concentric and eccentric loading has been compared in the present experimental work. The improvement in bearing capacity and reduction in settlement of the footing has also been assessed in terms of bearing capacity ratio (BCR) and settlement reduction factors (SRF). Even while comparing the economic aspects, geogrid skirts prove to be a viable alternative to the conventional skirts

Bearing capacity and deformation behavior of rigid strip footings on coral sand slopes

Porous coral sands formed by the remains of marine organisms are important foundation-filling materials for artificial island construction and other marine geotechnical projects. A typical situation is that the significantly reduced bearing capacity of a rigid footing adjacent to coral sand slopes threatens the safety and stability of the upper structures. In this study, a series of model-scale tests were conducted to investigate the bearing capacity and deformation behavior of a rigid strip footing resting on the top of coral sand slopes with consideration of the effects of edge distance, slope height, slope angle, number of geogrid layers, burial depth and spacing of the geogrid layer. The measured deformation field based on particle image velocimetry (PIV) technology indicates that the unreinforced coral sand slope is dominated by unilateral sliding patterns, and its bearing area is significantly smaller than that of the geogrid reinforced coral sand slope (GRCSS). The bearing capacity in unreinforced coral sand slopes increases with the increasing edge distance, and the decreasing slope height and angle. Although the geogrid reinforcement significantly improves the bearing capacity, it is also affected by the number of layers, burial depth and spacing between reinforcement layers. Besides, the reduction coefficient of bearing capacity (RCBC), the bearing capacity factor (Nγq) and the normalized bearing capacity (Nγq/NγqR) were further calculated and discussed based on the test results and classical bearing capacity theory.

Assessing the Effect of Underground Void on Strip Footing Sitting on a Reinforced Sand Slope with Numerical Modeling

This paper presents the results of the numerical analysis undertaken to investigate the effect of the underground void on the load-bearing capacity of a strip footing placed on an unreinforced and geogrid-reinforced sand slope with a void inside. The failure mechanism of the soil was also investigated. The numerical model was obtained using 2D plane-strain FEM analysis (in Plaxis software), in which the nonlinear Mohr-Coulomb model was utilized. The effects of various parameters such as the number of geogrid layers (N), the vertical distance ratio between the top of the cavity from the base of footing (H/B), the horizontal distance of void centerline to the footing center (X/B), on the behavior of footing are studied in this research. The results indicate that there is a critical zone under the footing in which the existence of void has no influence on the bearing capacity and stability of the footing. In addition, the use of geogrid reinforcement reduces the settlement and enhances bearing capacity. Finally, the bearing capacity factor and failure mechanism increase with increasing horizontal and vertical void distances ratios (X/B and H/B) and reinforcement layers.

Behavior of Vertically Confined Square Footing on Reinforced Sand under Centric Inclined Loading

Abstract This study presents the behavior of vertically confined square footing on geogrid-reinforced sand under centric inclined loading through a series of experimental tests. The load was applied at 5°, 10° and 20° angles of inclination with the vertical. The tests were conducted on surface footing, footing with confiner and footing with confiner and horizontal reinforcement configurations subjected to inclined loading. Parametric variations like depth of the confiner (d=1B, 1.5B, 2B), number of geogrid layers (N; varies with variation in depth of confiner), and spacing between horizontal reinforcements (Y=0.25B, 0.5B, 0.75B, 1B) have been investigated at the top surface dimension of confiner (D) as 1.0B, 1.5B and 2.0B (where B is the width of the model footing). Results show that combined effect of confiner and horizontal reinforcement increases the ultimate bearing capacity of footing significantly compared to only confiner for all angle of inclinations. It can also be observed that load bearing capacities decrease with increase in angles of inclination and record the minimum improvement at 20° angle of inclination. Improvement in bearing capacities and reduction in settlement of footing analyzed in terms of bearing capacity ratio (BCR) and settlement reduction factor (SRF) are compared for all footing configurations. To summarize, the test results showed that confiner along with reinforcement can be considered as an economic ground improvement technique for shallow foundations to counter against heavily inclined loading.

Experimental study on uplift behavior of shallow anchor plates in geogrid-reinforced soil

Geogrid reinforcement can significantly improve the uplift bearing capacity of anchor plates. However, the failure mechanism of anchor plates in reinforced soil and the contribution of geogrids need further investigation. This paper presents an experimental study on the anchor uplift behavior in geogrid-reinforced soil using particle image velocimetry (PIV) and the high-resolution optical frequency domain reflectometry (OFDR). A series of model tests were performed to identify the relationship between the failure mechanism and various factors, such as anchor embedment ratio, number of geogrid layers, and their location. The test results indicate that soil deformation and the uplift resistance of anchor plates are substantially influenced by anchor embedment ratio and location of geogrids, whereas the number of geogrid layers has limited influence. In reinforced soil, increasing the embedment ratio greatly improves the ultimate bearing capacities of anchor plates and affects the interlock between the soil and geogrids. As the embedment depth increases, the failure surfaces gradually change from a vertical slip surface to a bulb-shaped surface that is limited within the soil. The strain monitoring data shows that the deformations of geogrids are symmetrical, and the peak strains of geogrids can characterize the reinforcing effects.

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.

Effect of Different Reinforced Load Transfer Platforms on Geosynthetic-Reinforced Pile-Supported Embankment: Centrifuge Model Test

Geosynthetic-reinforced pile-supported (GRPS) embankment has been widely utilized in the railways and highways subgrade of soft clay area. The load transfer platform (LTP), consisting of sand layers and one or more layers of geosynthetic, is constantly used at the base of embankment to increase the load transfer to piles and reduce the differential settlement of embankment surface. However, the effect of different reinforced LTPs on the performances of GRPS embankment has not been fully understood. Eight centrifuge model tests were conducted to investigate the effect of five influence factors on deformation and load transfer of embankment, and tensile force of geogrid: placing geogrid or not, the number of geogrid layers, geogrid reinforced position, geogrid stiffness, wrapped-back geogrid setting in LTP. The results showed that the wrapped-back geogrid setting in the LTP was equivalent to anchoring the geogrid at the slope toe of embankment, which strengthened the reinforcement-soil interaction and restricted the pull-out displacement of geogrid to enhance the stiffness for LTP. The LTP reinforced with stiffer geogrid or multi-layer geogrid contributed to increase the stability and load transfer of embankment due to the increase of the integrity stiffness for LTP. When the geogrid was set at the middle of LTP, the performances of the GRPS embankment was enhanced due to the more interfaces between the geogrid and soil to improve the integrity stiffness of the LTP. The two-layer geogrid reinforced in the LTP could be the best choice to enhance the performance of the GRPS embankment under the comprehensive consideration of the performance and economy. The five setting ways of the reinforcement in LTP increased the integrity stiffness of LTP, which provided more methods to enhance the performances of the GRPS embankment.

Experimental and Numerical Investigation on Undrained Behavior of Geogrid Reinforced Pond Ash

Geogrid reinforced pond ash is an effective composite material, which can be utilized as a construction material for various geotechnical engineering purposes. In this study, both experimental and numerical investigations have been carried out on shear strength characteristics of unreinforced and geogrid reinforced pond ash samples under undrained condition. Consolidated undrained (CU) triaxial tests have been performed on 100 mm x 200 mm cylindrical ash samples under static compressive loading. The investigations include the influence of confining pressure and number of geogrid layers on stress–strain characteristics of pond ash. Finite element package PLAXIS 2D was used for numerical simulation of unreinforced and geogrid reinforced pond ash models under undrained condition. Both experimental and numerical results show that the peak deviatoric stress increases as confining pressure increases for both unreinforced and reinforced ash samples. For a particular confining pressure, with increase in number of geogrid layers the value of peak deviatoric stress increases and its corresponding strain decreases. The increase in peak deviatoric stress is about 27%–93% for one-layer geogrid reinforced sample and 37%–117% for two-layer geogrid reinforced sample compared to unreinforced ash sample. Finite element analysis shows a good match in the stress–strain plot with the experimental result.

Ispitivanje nekoherentnog tla armiranog geomrežom u uređaju za troosni posmik pri cikličkom opterećenju

In road base layers, geogrids assume the reinforcement or stabilization function where good interaction between geogrid and unbound base material is important. The cyclic triaxial test can be used for analysing interaction between geogrid and unbound base material. The paper includes an overview of research where cyclic triaxial test is primarily used for assessing the influence of parameters such as geogrid stiffness, geometry and aperture size, position and number of geogrid layers, on the interaction with the base layer material. The cyclic triaxial test can be used to determine contribution the geogrid application in non-cohesive materials has on the reduction of permanent deformations.

Contribution of using geogrid under a shallow foundation on sand subjected to static and repeated loads: Laboratory testing and numerical simulations

This paper focuses on the use of a certain punched and drawn geogrid to increase the bearing capacity of a circular shallow foundation subjected to a combination of static and repeated loads. In the experiments, the foundation is first subjected to a prespecified static load, afterwards, a repeated load derived in different proportions of the applied static load is superimposed to that static load. The variables investigated in the tests are the number of geogrid layers, the amplitude of repeated load, and the number of load cycles. The effect of these variables is also investigated by a finite element numerical modeling approach verified with one-dimensional site response analysis, and as a consequence of this effort that refers to the innovation of the study, the consistency between the results obtained from both methods is observed. The test results show that the displacements of the shallow foundation increase rapidly in the first 100 load cycles in all cases. After that, the rate of increase is reduced until about 2000 load cycles and the displacements become negligible. From the experiments, 2 geogrid layers were found to be quite effective in reducing displacements due to both static and dynamic loading cases. In other respects, finite element simulations of the physical experiment have produced numerical results in good agreement with the test results. Plus, the main contribution of the numerical simulation is to indicate the deformed mesh outputs of the model including the geogrids for the foregoing variables.

Influence of reinforcement-arrangements on dynamic response of geogrid-reinforced foundation under repeated loading

Dynamic tests were carried out on a square footing resting on unreinforced and reinforced foundation to investigate the influence of the geogrid-reinforcement arrangements on load-carrying characteristics of the footing under repeated loading. In this paper, the arrangements considered include the depth of the first geogrid layer (u), the number of geogrid layers (N) and the method of wraparound ends reinforcement. The settlement of footing, the strain of geogrid and the acceleration rate in soils were measured, and these results were analyzed in detail. The results showed that the bearing capacity of footing on reinforced foundations was at least 12% higher than that of unreinforced foundation. For the single-layer reinforced foundations, the bearing capacity first increased and then decreased with the increase of u. When u was equal to 0.6B (B = footing width), the bearing capacity was maximum, which was 21% and 15% higher than that of 0.3B and 0.9B, respectively. For the multi-layer reinforced foundations, the bearing capacity increased with increasing the N value from 1 to 3, and the maximum increase was 29%. Through analyzing the bearing capacity ratio (BCR) and the attenuation rate of acceleration (AAR), the influence of reinforcement arrangements on the bearing capacity of footing was in the order: the u value, the method of wraparound ends of reinforcement, the N value. The various reinforcement arrangements caused different dynamic responses, and the sensitivity of arrangement on acceleration responses was in the order: the N value, the method of wraparound ends of reinforcement and the u value. Additionally, it is also found that reinforcement arrangements significantly affected the geogrid strain and the failure mode of footing.

A new approach to optimizing the geogrid layout to maximize the bearing capacity of strip footing

This study presents a new approach to optimizing the layout of the geogrid layers to achieve the maximum bearing capacity of the strip footing under different loading conditions (Vertical (V), Horizontal (H) and eccentric (M) loads) using a numerical method. To find the best location of the geogrid layers in the current method, the optimum depth of each layer is obtained separately, which was not considered in previous studies. The effects of parameters such as different loading combinations, numbers and layout of geogrid layers on the ultimate bearing capacity of the strip footing have been studied. The results of the analyses are plotted in the form of dimensionless graphs. For different loading combinations, the optimum layout and number of reinforcing layers have been determined. The results show that the presence of the reinforced layers, at the optimum layout, significantly increases the ultimate bearing capacity of the strip footing, especially in the V and VM loading conditions. The optimum number of geogrid layers was different for different loading conditions. Based on the analyses, 7, 4 and 4 geogrid layers were obtained as the optimum number of reinforcement layers for the V, VH and VM loading conditions, respectively. Also, it was found that the position of each layer depends on the number of layers. In this study, the position of the first layer from the foundation (u/B) was varied by increasing the number of reinforcement layers and the loading conditions. In the VM loading condition, the geogrid reinforcement effect on the bearing capacity is more prominent with respect to the VH loading conditions. The increase of the bearing capacity in the VM loading condition at the optimum layout of reinforcement (N = 4) is about 100 %, compared to the bearing capacity of the unreinforced soil.

Physical and numerical modelling of strip footing on geogrid reinforced transparent sand

This paper presents the results of laboratory scale plate load tests on transparent soils reinforced with biaxial polypropylene geogrids. The influence of reinforcement length and number of reinforcement layers on the load-settlement response of the reinforced soil foundation was assessed by varying the reinforcement length and the number of geogrid layers, each spaced at 25% of footing width. The deformations of the reinforcement layers and soil under strip loading were examined with the aid of laser transmitters (to illuminate the geogrid reinforcement) and digital camera. A two-dimensional finite difference program was used to study the fracture of geogrid under strip loading considering the geometry of the model tests. The bearing capacity and stiffness of the reinforced soil foundation has increased with the increase in the reinforcement length and number of reinforcement layers, but the increase is more prominent by increasing number of reinforcement layers. The results from the physical and numerical modelling on reinforced soil foundation reveal that fracture of geogrid could initiate in the bottom layer of reinforcement and progress to subsequent upper layers. The displacement and stress contours along with the mobilized tensile force distribution obtained from the numerical simulations have complimented the observations made from the experiments.

Effect of geogrid reinforcement on soil - structure – pipe interaction in terms of bearing capacity, settlement and stress distribution

In this study, the contribution of single and multiple layers of geogrids to bearing capacity and stress behavior was determined by laboratory experiments. The effects of parameters such as the depth of the first geogrid, the vertical spacing between the geogrid layers and the number of geogrid layers on the bearing capacity and settlement behavior of soil and stress distribution on geogrid and pipe by using strain gauges have been investigated. The results of experiments were given in dimensionless form of bearing capacity ratio (BCR), settlement reduction factor (SRF) and stress capacity ratio (SCR). As a result of experiments, the contribution of the geogrid on the soil-structure-pipe interaction has been observed together with the stress distribution on the geogrid contributed to the efficient use of the appropriate geogrid capacity.

Experimental study and neural network modelling of expansive sub grade stabilized with industrial waste by-products and geogrid

For highway construction projects, expansive sub grade improvement is one of the prime and major processes. The strength of the sub grade soil is indicated by its California bearing ratio (CBR) value which is quite expensive and time consuming. In order to overcome this situation, the present research aims in predicting the soaked CBR value for the stabilized soils by Multiple Regression Analysis (MRA) and Artificial Neural Network (ANN) modeling. Experiments were done to stabilize the expansive soils with the addition of varying percentages of industrial waste by-products (Coal ash, Bagasse ash and Groundnut shell ash) with geogrid layers. Ash type, Mix proportion, Atterberg limits, Maximum dry density, optimum moisture content and number of geogrid layers were taken as input variables and soaked CBR value as output variable for the regression based models. It is observed that ANN model is accurate than the MRA model in predicting the soaked CBR value of expansive soil stabilized with industrial waste materials, both the measured experimental values and predicted values are in good agreement. Levenberg-Marquardt back propagation shows maximum R value of 0.94317 and minimum MSE value of 0.49.