Geocell-reinforced Foundation Research Articles

Performance of Artificial Neural Network and Modified Gravitational Search Algorithm Models to Predict Vibration Response of Geocell Reinforced Based Weak Sand

The use of a fast evolving artificial intelligence technology (AIT) to forecast the vibration response of maritime soil based on geocells is explored in this research. The vibration response is represented by an indicator called peak particle velocity (PPV). For the purpose of predicting PPV, the artificial intelligence techniques Artificial Neural Network (ANN) and Modified Gravitational Search Algorithm (MGSA) are employed. To create the dataset for the model, a number of field vibration tests were first performed over the geocell-reinforced beds. PPV variation was investigated by varying the test variables—footing embedment, dynamic load, infill material modulus, width, and depth of geocell mattress placement—during the test performed. The various statistical indicators were determined in order to evaluate the prediction performance of a constructed model. Plate load results on geocell-reinforced foundation beds have been used to validate the proposed hybrid ANN-MGSA model. High accuracy and consistency were found when the findings of the ANN-EHO, JSA, MOA, and RNN method were compared, particularly at predicted and actual resolution levels. A parametric sensitivity has also been examined in order to better understand the behaviour of geocell-reinforced structures.

Performance of Artificial Neural Network and Modified Gravitational Search Algorithm Models to Predict Vibration Response of Geocell Reinforced Based Weak Sand

The use of a fast evolving artificial intelligence technology (AIT) to forecast the vibration response of maritime soil based on geocells is explored in this research. The vibration response is represented by an indicator called peak particle velocity (PPV). For the purpose of predicting PPV, the artificial intelligence techniques Artificial Neural Network (ANN) and Modified Gravitational Search Algorithm (MGSA) are employed. To create the dataset for the model, a number of field vibration tests were first performed over the geocell-reinforced beds. PPV variation was investigated by varying the test variables—footing embedment, dynamic load, infill material modulus, width, and depth of geocell mattress placement—during the test performed. The various statistical indicators were determined in order to evaluate the prediction performance of a constructed model. Plate load results on geocell-reinforced foundation beds have been used to validate the proposed hybrid ANN-MGSA model. High accuracy and consistency were found when the findings of the ANN-EHO, JSA, MOA, and RNN method were compared, particularly at predicted and actual resolution levels. A parametric sensitivity has also been examined in order to better understand the behaviour of geocell-reinforced structures

Simulation of Geocell-Reinforced Foundation Using Particle Flow Code

Interlock-enhanced integral geocells are three-dimensional (3D) cellular structures. They are widely used in foundations to increase the load-bearing capacity and reduce the foundation settlement. However, as a new kind of reinforcement, some key considerations, such as the interface between the soil and the interlock-enhanced integral geocells and the failure mode, and mechanics of the interlock-enhanced integral-geocell-reinforced soil foundations, are not clarified yet. In this study, we investigated geocell-reinforced foundation using particle flow code (PFC3D) based on the discrete element method. The initial states and loading processes were simulated according to the finished model texts. The stress distribution, particle displacements, and contact forces were examined to determine the contribution of the interlock-enhanced integral geocells to the reinforced foundations. The interface between particles and the interlock-enhanced integral geocells, the failure mode, and the reinforcement mechanism of the interlock-enhanced integral-geocell-reinforced foundations are discussed. The numerical simulation results reveal that the characteristics of the interlock-enhanced integral-geocell-reinforced foundation can be well simulated by PFC3D. Soil particles are not displaced under the applied load because of the sidewalls of the interlock-enhanced integral geocells. The interlock-enhanced integral geocells allow soil particles penetrate from one side of the cell to the other owing that geocells have a 3D network structure with aperture geometry. Therefore, lateral deformation or potential strain in the soil is restrained. The interlock-enhanced integral geocell distributes the applied load over a wider area, thus increasing the shear strength of the composite system. The load-bearing capacity of the soil foundation is improved by the interlock-enhanced integral geocell.

Analysis and research on the bearing capacity of geocell reinforced cushion subgrade in liyu expressway

This paper takes the filling roadbed of the Lipu-Yulin Expressway (Liyu Expressway) project in the Guangxi Zhuang Autonomous Region as the backup project. Numerical simulation research is conducted by employing the general finite-element analysis software ABAQUS. The three-dimensional numerical models of the unreinforced soil embankment and reinforced embankment are formulated and the subgrade’s ultimate bearing capacity is calculated and solved by the elastoplastic finite element method. Effects of planar and three-dimensional reinforcement, i.e., geotextile and geocell, on the ultimate bearing capacity of the foundation are calculated and analysed. Simultaneously, the strength and deformation characteristics of geocells and geotextiles under embankment loads are studied. Research results show that the enhanced bearing capacity of geocell-reinforced foundation in this paper is increased by about 30%, which is greater than that of the planar reinforced material. This research results in this paper provide reference and theoretical basis for designing and analysing geocell-reinforced embankment in actual engineering practices.

Effect of Influencing Parameters on the Vibration Isolation Efficacy of Geocell Reinforced Soil Beds

This manuscript evaluates the effect of various influencing factors on the vibration mitigation efficiency of geocell-reinforced foundation beds. Parameters investigated include the width of geocell, depth of placement of geocell below the footing, depth of embedment of footing, infill materials, and the dynamic force level of the excitation. The effect of aforesaid parameters was studied by performing field vibration tests over the reinforced test beds of 3.6 m × 3.6 m × 1.2 m. To understand the vibration isolation efficacy, different vibration indicators, viz., displacement amplitude, peak particle velocity (PPV), and peak acceleration were evaluated. From the results, reinforcing the soil bed with geocell was found to be a worthwhile approach to control the vibration parameters. For achieving the maximum isolation, the optimum width and depth of placement of geocell were found to be 5B and 0.1B respectively. At its optimum width and depth of placement, the peak particle velocity was reduced by 50%. Similarly, it was observed that the 53% drop in the peak displacement amplitude of the foundation bed. Vibration parameters in the geocell reinforced case were found attenuated with the increase in footing embedment and modulus of infill material. On the other hand, the vibration parameters of the unreinforced and geocell reinforced cases were amplified distinctly due to the increase in dynamic excitation.

Contact Pressure Distribution on Subgrade Soil Underlying Geocell Reinforced Foundation Beds

High contact stresses generated in the foundation soil, owing to increased load, causes distress, instability and large settlements. Geocell reinforcement is being widely used for the performance improvement of foundation beds. Pressure distribution on subgrade soil in geocell reinforced foundation beds is studied through model tests and numerical analysis. The test data indicates that with provision of geocell reinforcement the contact pressure on the subgrade soil reduces significantly. Consequently, the subgrade soil tends to remain intact until large loadings on the foundation leading to significant performance improvement. Through numerical analysis it is observed that the geocells in the region under the footing were subjected to compression and beyond were in tension. This indicates that the geocell reinforcement right under the footing directly sustains the footing loading through mobilisation of its compressive stiffness and bending rigidity. Whereas, the end portions of the geocell reinforcement, contribute to the performance improvement in a secondary manner through mobilisation of anchorage derived from soil passive resistance and friction.

Effect of infill materials on vibration isolation efficacy of geocell-reinforced soil beds

This paper investigates the isolation efficacy of geocell-reinforced foundation beds infilled with different materials through a series of block resonance tests. The geocell made with a novel polymeric alloy (NPA) was used in the experimental investigation. In total, five different cases — namely, unreinforced, geocell-reinforced silty sand, geocell-reinforced sand, geocell-reinforced slag, and geocell-reinforced aggregate — were considered. Presence of the geocell has resulted in improvement of screening efficacy of the foundation bed regardless of the infill material. The displacement amplitude of the geocell-reinforced bed cases was reduced by 68%, 64%, 61%, and 59%, respectively, for aggregate, slag, sand, and silty sand infill cases as compared to the unreinforced condition. Maximum isolation efficiency was observed in the presence of aggregate, among the four different infill materials. In the presence of aggregate infill, the shear modulus of the foundation bed was improved by 150%. Similarly, the peak particle velocity and peak acceleration were reduced by 57% and 48%, respectively. Further, the efficacy of mass spring dashpot (MSD) analogy was studied in predicting the frequency–displacement response of different reinforced cases. From the analytical study, a significant improvement in damping ratio of the foundation bed was observed in the presence of geocell reinforcement.

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.

A design scheme for geocell-reinforced foundations based on the lower bound limit analysis method

Results of laboratory tests on geocell-reinforced soils indicate negligible change in the internal friction angle and development of an apparent cohesion. If sufficient apparent cohesion to withstand applied loads on foundations can be determined, then a suitable kind of soil-geocell composite may be selected among pretested ones by laboratory means. In the present study, using numerical methods of lower bound limit analysis, the required apparent cohesion in the geocell layer to bear the applied load on strip foundations has been determined by back analysis. Effects of contributing factors were evaluated on the results for single and double layer reinforcements.

Efficiency of cellular geosynthetics for foundation reinforcement

A numerical simulation of geocell-reinforced foundation beds is reported. The three-dimensional geocells and soil are simulated separately using FLAC3D Finite Difference software. A single geocell-reinforced soil is modeled and the results compared with those from a laboratory test in the literature. The model is extended to geocell foundation beds. The placement conditions in which the geocell layers have the highest efficiency (highest bearing capacity with the lowest cost) are determined. Also, a comparison is made between the performance of cellular geosynthetic reinforcement and a planar form with the same mass of used material (as two reinforcing systems with similar materials but different behavior mechanisms) to identify the system with the greatest efficiency. The analyses are performed for both sandy and clay beds and their results are compared.

Influence of reinforcement stiffness and strength on load-settlement response of geocell-reinforced sand bases

Improvement in the performance of a strip footing supported on geocell-reinforced sand bed is investigated through series of experimental tests on a reduced scale physical model. Geocells with scaled-down mechanical and geometrical properties produced from various material types consisting of woven geotextile, nonwoven geotextile and biaxial geogrid are used as the reinforcement and the influence of geocell strength and stiffness on the enhancement of bearing capacity and settlement of the surface footing is described. The results indicate that stiffness of geocell makes a significant contribution on the performance of geocell-reinforced soil. For the geocells used in the tests with the height equal to footing width, for example at footing settlement ratio of 6%, improvement in the bearing capacity of geocell with the stiffest material is found to be 1.5 times the geocell with the softest material. The failure mechanism of geocell-reinforced foundation system has been shown to depend highly on geocell modulus and height. It is also concluded that ultimate tensile strength of geocell material is generally not influential at load-settlement behaviour of the footing at practical settlement levels. However, if flexural rupture of reinforcement controls the failure mechanism, geocell strength affects the ultimate bearing capacity.

A simplified method for predicting the settlement of circular footings on multi-layered geocell-reinforced non-cohesive soils

Multiple layers of geosynthetic reinforcement, placed below foundations or in the supporting layers of road pavements, can improve section performance through several mechanisms, leading to reduction in stresses and deformations. This paper aims to present a new analytical solution, based on the theory of multi-layered soil system to estimate the pressure–settlement response of a circular footing resting on such foundations, specifically those containing geocell layers. An analytical model that incorporates the elastic characteristics of soil and reinforcement is developed to predict strain and confining pressure propagated throughout an available multi-layer system, is proposed. A modified elastic method has been used to back-calculate the elastic modulus in terms of strain and confining pressure with materials data extracted from triaxial tests on unreinforced and geocell-reinforced soil samples. The proposed model has been validated by results of plate load tests on unreinforced and geocell-reinforced foundation beds. The comparisons between the results of the plate load tests and proposed analytical method reflected a satisfactory accuracy and consistency, especially at expected, practical, settlement ratios. Furthermore, to have a better assessment of geocell-reinforced foundations' behavior, a parametric sensitivity has been studied. The results of this study show that the higher bearing pressure and lower settlement were achieved when number of geocell layer, secant modulus of geocell and the modulus number of the soil were increased. These results are in-line with the experimental results of the previous researchers. The study also permits the limits of effective and efficient reinforcement to be determined.

Influence of subgrade strength on the performance of geocell-reinforced foundation systems

ABSTRACT: Physical model tests were performed on geocell-reinforced foundation systems with circular footings to study the influence of the strength of the subgrade layer. Model tests were conducted with a 150 mm diameter circular footing supported on foundation beds with varied configurations. Three different series of tests were conducted using a clay subgrade with undrained cohesion in the range of 7–60 kPa and dense sand at 80% of relative density. The results showed that the performance of the geocell-reinforced foundation systems was highly dependent on the subgrade strength. A maximum improvement factor of about 11.6 was observed for very soft subgrade with cu= 7 kPa, which decreased to about 3 for stiffer subgrade having cu= 30 kPa under similar test conditions and configuration. In addition, the variation of bearing capacity improvement factors was observed to be significantly influenced by footing settlement and geocell height.

Numerical simulation of geocell-reinforced sand and clay

A numerical simulation of laboratory model tests was carried out to develop an understanding of the behaviour of geocell-reinforced sand, and soft clay foundation beds under a circular footing. The influence of the geometrical parameters of the geocell (width, b and height, h) on the overall performance of the footing was investigated and the pressure–settlement responses of geocell-reinforced foundation beds were predicted and compared with the unreinforced test results. Simulations were also carried out on conventional-type planar geogrid reinforcement to study the relative performance of both reinforcement forms. The influence of the boundary constrains on the behaviour of the foundations was also studied. In all the cases, good agreement between the results obtained from numerical simulations and laboratory experiments was observed. The results demonstrated that the geocell mattress redistributed the footing pressure over a wider area thereby improving the performance of the footing. The pressure–settlement responses corresponding to geocell-reinforced beds were found to be much stiffer in comparison with the unreinforced case indicating that a substantial reduction in footing settlement can be ascertained. The influence of rigid boundaries on the results of reinforced foundation beds in this study was found to be negligible.

Behavior of Geocell-Reinforced Sand under a Vertical Load

Geocells have a three-dimensional cellular structure, which can be used to stabilize foundations by increasing bearing capacity and reducing settlements. However, a considerable gap exists between the applications and the theories for the mechanisms of geocell-reinforced foundations. An experimental and numerical study on the behavior of geocell-reinforced sand under a vertical load is presented. A single geocell was filled with sand and subjected to a vertical load to failure. This test process was modeled by using the FLAC3D numerical software to investigate the mechanisms of geocell and sand interactions. Experimental and numerical results both demonstrated that the geocell increased the ultimate bearing capacity and the modulus of the sand. The numerical results include the distributions of displacements in the sand and geocell walls and the distributions of tensile stresses and shear stresses acting on the geocell walls. The numerical results for geocell-reinforced sand are compared to those for sand without geocell.

Performance of surface footing on geocell-reinforced soft clay beds

This paper presents the results of laboratory model tests carried out to develop an understanding of the behaviour of geocell-reinforced soft clay foundations under circular loading. Natural silty clay was used in this study. The geocells were prepared using biaxial polymer grid. The performance of the reinforced bed is quantified using non-dimensional factors i.e., Bearing capacity improvement factor (If) and Percentage reduction in footing settlement (PRS). The test results demonstrate that the geocell mattress redistributes the footing load over a wider area thereby improving the performance of the footing. The load carrying capacity of the clay bed is increased by a factor of up to about 4.5 times that of unreinforced bed. From the pressure-settlement responses, it is observed that the geocell-reinforced foundation bed behaves as a much stiffer system compared to the unreinforced case indicating that a substantial reduction in footing settlement can be achieved by providing geocell reinforcement in the soft clay bed. The maximum reduction in footing settlement obtained with the provision of geocell mattress of optimum size placed close to the footing is around 90%. Further improvement in performance is obtained with provision of an additional planar geogrid layer at the base of the geocell mattress.

Effects of base geogrid on geocell-reinforced foundation beds

The effect of a base geogrid layer below the geocell mattress in sand, sand overlying soft clay, and soft clay foundation beds has been studied using a series of laboratory scale load tests. A rigid circular model footing was used to apply static monotonic loading on the foundation beds with and without geocell reinforcement. The model test results show that the provision of an additional layer of planar geogrid at the base of the geocell mattress further increases the performance of the footing in terms of bearing capacity and reduction in surface heave of the foundation bed. It is also observed that the beneficial effect of the base geogrid layer becomes negligible with increasing height of the geocell mattress beyond the influence of the depth of the footing. Strain measurements in the base geogrid layer indicate that it is more effective with the limited heights of the geocell mattress. The earth pressure cells embedded in the subgrade soil provide evidence that when the base geogrid is provided below the geocell mattress, the footing pressure is distributed more uniformly over an extended area.