The influence of a cyclic loading history on soil-geogrid interaction under pullout condition (original) (raw)
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Geotextiles and Geomembranes, 2009
This paper deals with some results of a wide experimental research carried out in order to study factors affecting cyclic and post-cyclic pullout behaviour of different geogrids embedded in a granular soil. The new test procedure developed (multistage pullout test) and the relative results are described. In particular, test results obtained using the constant rate of displacement (CRD) and the multistage pullout tests highlighted the influence of the different factors involved in the research (cyclic load amplitude and frequency, vertical confining stress, geogrid tensile stiffness and structure) both on the peak pullout resistance and on the peak apparent coefficient of friction mobilized at the interface.
Pullout tests are necessary in order to study the interaction behaviour between soil and geosynthetics in the anchorage zone, hence, the test results have direct implications in the design of reinforced soil structures. This paper presents an evaluation of the soil-geogrid interaction, conducted to quantify the contributions of the frictional and the bearing components of the pullout resistance of geogrids. Based on the data obtained by authors, a stress transfer model has been implemented to predict the results of large-scale pullout tests using the load transfer curves approach. In particular, in the proposed stress transfer model the geometry of the elements on which the bearing resistance mobilizes, the soil dilatancy effects, the geogrid extensibility and the interference phenomena (between transversal bearing members) are taken into account. The comparison between theoretical and experimental results shows a good agreement, thus confirming the reliability of the proposed approach.
Geotextiles and Geomembranes, 2012
This paper deals with the results of a wide experimental research carried out in order to study factors affecting the cyclic and post-cyclic pullout behaviour of different geogrids embedded in a compacted granular soil. In a previous paper (Moraci and Cardile, 2009) the influence of the tensile cyclic load frequency and amplitude, vertical confining stress and geogrids structure on the pullout resistance and on the interface apparent coefficient of friction was studied. In this paper, the influence of the same factors on the pullout behaviour in terms of accumulated displacements and deformations are analysed.
HDPE geogrid-residual soil interaction under monotonic and cyclic pullout loading
Geosynthetics International, 2020
The understanding of soil-geosynthetic interaction under cyclic loading conditions is essential for the safe design of geosynthetic-reinforced soil structures subjected to repeated loads, such as those induced by road and railway traffic and earthquakes. This paper describes a series of large-scale monotonic and multistage pullout tests carried out to investigate the behaviour of an HDPE uniaxial geogrid embedded in a locally available granite residual soil under monotonic and cyclic pullout loading. The effects of the pullout load level at the start of the cyclic stage, cyclic load frequency and amplitude, number of cycles and soil density on the load-strain-displacement response of the reinforcement are evaluated and discussed. Test results show that the cumulative displacements measured along the length of the geogrid during cyclic loading increased significantly with the pre-cyclic pullout load level and the load amplitude. In contrast, the cumulative cyclic displacements were f...
A laboratory study on pull-out resistance of geogrid in clay soil
Measurement, 2019
Geosynthetics such as geotextiles, geogrids and geocells are outstanding materials for reinforcement of soils. Recently, reinforcing the clay soils with geosynthetics, by increasing the bearing capacity and decreasing over consolidation, was used increasingly in geotechnical applications. The behavior of soil with reinforced material is crucial on design of reinforced soil. In this study the interaction between geogrid and clay soil was investigated by pulling out the geogrid experimentally with the help of direct shear tests machine. In experiments the geogrid was placed on shear surface that was the midpoint of test mold. The soil samples were prepared with different water content that was including optimum water content (OWC). A special cap was designed to pull-out the reinforcing material through the soil sample. According to experimental results, the variation of pullout load against displacement seems to be similar to classical load-displacement behavior of soil and it increases when the normal stress increases. Under the same normal stresses, pull-out load observed to be greater when the soil sample has OWC. At stress level =27,2 kPa, when water contents of soil samples increase 60%, the pullout loads increase approximately 30%. These observations can be interpreted the interlocking between soil and geogrid is stronger at OWC. It is also showed from the tests results that pullout load values are generally greater than interfacial strength of soil samples.
Geogrids are one of the most common types of geosynthetic used for soil reinforcement. In particular, the use of geosynthetics has unique advantages over other soil strengthening techniques, because of technical, economic, and sustainability reasons. The redistribution of internal stresses within reinforced soil mass and its deformations depends on soil shear strength, reinforcement tensile strength and stiffness, and on interface stress mechanisms between soil and reinforcement. The results of pullout tests carried out on two extensible geogrids embedded in a compacted granular soil, in terms of peak pullout resistance at soil-geosynthetic interface, are analyzed. Some considerations about deformation behavior analysis are also reported. The equipment incorporates two sleeves near the slot at the front wall of the pullout box to avoid front wall effects, as recommended by researchers. The pullout apparatus is capable producing the confined failure of a geosynthetic specimen by using an internal clamp placed inside the soil beyond the sleeves.
Geotextiles and Geomembranes - GEOTEXT GEOMEMBRANE, 2006
Pullout tests are necessary in order to study the interaction behaviour between soil and geosynthetics in the anchorage zone; hence, the resulting properties have direct implications on the design of reinforced soil structures.Several experimental studies showed the influence of different parameters (reinforcement stiffness, geometry and length, applied vertical effective stress, and geotechnical properties of soil) on the peak and on residual pullout resistance.On the basis of the results of the tests carried out by Moraci and Recalcati [2005. Factors affecting the pullout behaviour of extruded geogrids embedded in a compacted granular soil. Geotextiles and Geomembranes, submitted for publication], a new theoretical method was developed to determine the peak and the residual pullout resistance of extruded geogrids embedded in a compacted granular soil. The method is capable of evaluating both the bearing and the frictional components of pullout resistance, taking into account the r...
Soil-Geogrid Reinforcement Interaction by Pullout and Direct Shear Tests
Geotechnical Testing Journal, 1995
This paper reports the results of a study to investigate the soil-geocell reinforcement using pullout and direct shear tests. The behaviour of soil-geocell interaction is characterized based on shear stress-displacement behaviour and shear strength properties. The results from pullout tests show strain hardening behaviour of pullout load-displacement curves. In direct shear tests, strain softening behaviour was observed on both reinforced and unreinforced soil where the provision of geocell increased the shear strength of the soil due mainly to higher apparent cohesion and internal friction angle. The degree of interlocking on dense soil and additional friction on the interface between soil and geocell reinforcement may have attributed to increase in shear strength. RESUMEN Este artículo presenta los resultados de un estudio para investigar el refuerzo del mecanismo suelo-geocelda ante pruebas de tensión y corte directo. El comportamiento de la interacción entre el suelo y la geocelda es caracterizado en función del comportamiento entre el desplazamiento y el esfuerzo cortante y las propiedades de resistencia del mecanismo suelo-geocelda. Los resultados de las pruebas de tensión demuestran un comportamiento de endurecimiento por deformación en las curvas de carga tensión vs desplazamiento. En pruebas de corte directo, se pudo apreciar un comportamiento de ablandamiento ante la deformación para las condiciones de suelo reforzado y sin refuerzo donde la geocelda incrementó la resistencia al corte del suelo debido principalmente a una mayor cohesión aparente y un incremento en el ángulo de fricción interno. El grado de entrelazado en suelos densos y la fricción adicional en el punto de contacto entre el suelo y el refuerzo de geocelda podría ser atribuido al incremento en la resistencia al corte.
Experimental and Numerical Analysis of Geogrid-Reinforced Soil Systems
Arabian Journal for Science and Engineering, 2018
Geosynthetic-reinforced soil technique has been increasingly used in civil engineering practice over the last two decades. Understanding the response of soil reinforcements to pullout loading is considered to be essential to any successful analysis and design of reinforced soil structures. This paper presents the results of a series of experimental investigation supported by numerical analysis to examine the pullout behavior of geogrid reinforcing element under static loading. The purpose of the study is to numerically simulate the response of geosynthetic reinforcement to static pullout loading. Finite element Plaxis software was used to model the mechanical behavior of the interface between geogrid-soil dissimilar materials. The numerical model was calibrated and validated using the experimental data generated during this investigation. The results of this study demonstrate that numerical 3D model can give good predictions of the pullout behavior of geogrid-reinforced soil systems under static loads.
Geotextiles and Geomembranes, 1993
The use of polymeric geogrids in reinforcement applications is progressing rapidly with the current commercial availability of the products of at least ten different manufacturers. While all of these products consist of an interconnected set of longitudinal and transverse ribs, their similarity ends at this point. Major variables consist of rib size and strength, aperture size, type of polymer, and method of joining the intersecting ribs. This paper attempts to model the use of a "generic'geogrid in the anchorage, or pullout, mode of behavior. It does so by deriving an incremental finiteelement formulation to simulate the non-linear response of the geogrid to pullout. Polynomial and hyperbolic functions are used to represent the loadextension behavior of the geogrid and the soil-geogrid-interaction fn'ctional and bearing properties. Three models are incorporated in the analysis to simulate the deformation of the transverse ribs. Highly flexible ribs are assumed to take a parabolic shape and to act as strings, whereas short stiff ribs are considered not to deflect during pulling. Intermediate cases are analyzed by assuming the ribs to behave as beams deflecting under load. Upon development of the program, it is illustrated on an example geogrid. The behavioral trends of the various components of friction and bearing are generated with respect to the percentage mobilized of the pullout load. Of major interest is an understanding of the relative contribution of the various components, particularly the amount of force that must be transmitted through the rib junctions.