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The definition of rigid floating piles in engineering applications remains ambiguous. This paper develops a numerical model of piled embankments and the modeling method is verified through engineering cases. Utilizing this model, the critical bearing capacity of the foundation for rigid floating piles is firstly determined to be approximately 150 kPa. Subsequent parametric studies show that soil arching in a rigid floating piled embankment begins to occur when the ratio of the embankment height to the clear pile spacing H/(s − a) ≥ 1.6. However, plastic failure does not occur in rigid floating piled embankments due to the weaker foundation, indicating that soil arching cannot fully develop. Finally, factors of the embankment fill properties are examined and it is shown that the large friction angle and high cohesion greatly enhance soil arching and reduce settlement in the embankment. The vertical stress above the subsoil decreased by 34.9% with an increase in the friction angle from 20° to 40°. Also shown is that the increase in the cohesion from 1 kPa to 7 kPa reduced the settlement on the top of and the base of embankment by approximately 72% and 58%, respectively. It has also been found that rigid floating piles rely on end resistance and skin friction to sustain the superimposed load. [ABSTRACT FROM AUTHOR]

The piled embankment represents one of the solutions for the realization of a soil body on a compressible subsoil where extended settlement or insufficient stability threatens the serviceability of related structures. Widely adopted analytical design procedures were analyzed: Marston's formula and Hewlett and Randolph method contained in the British standard BS 8006-1, the German regulation EBGEO and the Dutch regulation CUR 226. Using these recommendations, the theoretical values of the individual parts of the load acting in the embankment and, subsequently, the values of the axial strain or tensile forces in the reinforcement were determined and compared with experimental data obtained from the tests in the large-scale physical model. For the presented case, without subsoil support, CUR 226 with the inverse load, which is recommended in the case of subsoil with low bearing capacity, shows better coincidence with the measured data. Overall, EBGEO and CUR 226 can be considered to be close to the real behavior of the piled embankment. Because of the frequent utilization of geosynthetic reinforcement and possible changes of subsoil parameters during the service life of the piled embankment, a rheological process of its elements should be investigated during the design process. [ABSTRACT FROM AUTHOR]

The definition of rigid floating piles in engineering applications remains ambiguous. This paper develops a numerical model of piled embankments and the modeling method is verified through engineering cases. Utilizing this model, the critical bearing capacity of the foundation for rigid floating piles is firstly determined to be approximately 150 kPa. Subsequent parametric studies show that soil arching in a rigid floating piled embankment begins to occur when the ratio of the embankment height to the clear pile spacing H/(s − a) ≥ 1.6. However, plastic failure does not occur in rigid floating piled embankments due to the weaker foundation, indicating that soil arching cannot fully develop. Finally, factors of the embankment fill properties are examined and it is shown that the large friction angle and high cohesion greatly enhance soil arching and reduce settlement in the embankment. The vertical stress above the subsoil decreased by 34.9% with an increase in the friction angle from 20° to 40°. Also shown is that the increase in the cohesion from 1 kPa to 7 kPa reduced the settlement on the top of and the base of embankment by approximately 72% and 58%, respectively. It has also been found that rigid floating piles rely on end resistance and skin friction to sustain the superimposed load.

The piled embankment represents one of the solutions for the realization of a soil body on a compressible subsoil where extended settlement or insufficient stability threatens the serviceability of related structures. Widely adopted analytical design procedures were analyzed: Marston’s formula and Hewlett and Randolph method contained in the British standard BS 8006-1, the German regulation EBGEO and the Dutch regulation CUR 226. Using these recommendations, the theoretical values of the individual parts of the load acting in the embankment and, subsequently, the values of the axial strain or tensile forces in the reinforcement were determined and compared with experimental data obtained from the tests in the large-scale physical model. For the presented case, without subsoil support, CUR 226 with the inverse load, which is recommended in the case of subsoil with low bearing capacity, shows better coincidence with the measured data. Overall, EBGEO and CUR 226 can be considered to be close to the real behavior of the piled embankment. Because of the frequent utilization of geosynthetic reinforcement and possible changes of subsoil parameters during the service life of the piled embankment, a rheological process of its elements should be investigated during the design process.

Geogrid-reinforced piled embankments (GRPEs) provide an economical and effective way to construct highways and railways on soft soil foundations. This paper proposed a new design method for GRPEs. The method was based on the soil arching and tensioned-membrane effects, the bearing capacity of the subsoil was considered as well. The originality of the proposed method lies in considering the stress history of the subsoil, and different over-consolidation ratios (OCRs) were used in calculating the settlement of subsoil. This design method, initially, established the vertical equilibrium of the unit body between the pile caps immediately above the subsoil. After that, the design charts were produced by solving the overall equilibrium equation from which engineers can intuitively obtain the maximum strain of reinforcement, and the tensile force can be used in the ultimate limit state analyses. The design method was then validated by three case studies, which showed good reliability with the maximum error being less than 18%. Parameter study results indicated that the maximum strain of reinforcement for the under-consolidated soil was 80–120% larger than that for normally consolidated soil and more than four times greater than that for over-consolidated soil. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Zhejiang University: Science A is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Geogrid-reinforced piled embankments (GRPEs) provide an economical and effective way to construct highways and railways on soft soil foundations. This paper proposed a new design method for GRPEs. The method was based on the soil arching and tensioned-membrane effects, the bearing capacity of the subsoil was considered as well. The originality of the proposed method lies in considering the stress history of the subsoil, and different over-consolidation ratios (OCRs) were used in calculating the settlement of subsoil. This design method, initially, established the vertical equilibrium of the unit body between the pile caps immediately above the subsoil. After that, the design charts were produced by solving the overall equilibrium equation from which engineers can intuitively obtain the maximum strain of reinforcement, and the tensile force can be used in the ultimate limit state analyses. The design method was then validated by three case studies, which showed good reliability with the maximum error being less than 18%. Parameter study results indicated that the maximum strain of reinforcement for the under-consolidated soil was 80–120% larger than that for normally consolidated soil and more than four times greater than that for over-consolidated soil.

There are currently several national standards or regulations for the design of the piled embankment, providing suitable solutions for foundation of transport structure on soft, high compressible subsoil, [1]. The most widely used and the best-known standard is British Standard BS8006 [2], which was confronted with another analytical design methodologies (Ebgeo, CUR). Today’s popularity and versatility of FEM numerical models brings many advantages, which analytical methods cannot achieved, but must be verified by proposed scaled physical model, which was currently being developed by Department of Geotechnics, University of Žilina.

The structural optimization of basal reinforced piled embankments is usually conducted by examining design alternatives while ignoring the inherent variability of soil properties and studying only a limited number of structural variables. As an alternative, this paper proposes a hybrid modeling framework to introduce soil property uncertainty into embankment settlement calculations. This is important because settlement is critical in the serviceability assessments considered during structural optimization. The proposed framework consists of uncertainty modeling, finite element method, surrogate modeling, and probabilistic analysis. More specifically, a neural network with Monte Carlo dropout that accounts for uncertainty is employed to correlate the soil properties which affect the long-term performance of embankments over soft clay. Next, a coupled finite element analysis is performed using two constitutive soil parameters generated by the neural network to predict post-construction settlements. Combining the finite element (input source) with a surrogate model (data-driven approximation) yields substantial settlement outcomes for structure evaluations. A case study is then used to validate the effectiveness and applicability of this framework. Finally, an exhaustive search approach is used to design a cost-effective improved ground within ultimate and serviceability limit state constraints. Pareto front is computed using a logistic function at different settlement reliability levels. [ABSTRACT FROM AUTHOR]

Piled embankments, which have many advantages, have been widely employed in the construction of railways over soft soil. However, the load transfer mechanism and deformation characteristic induced by train loading, which has great importance for piled embankment design, are not well known and deserve more research attention. In this paper, a three-dimensional numerical model of a piled embankment subjected to train loading is proposed and calibrated by test results, which considers the dynamic behavior of soft clays by a simplified dynamic constitutive model based on bounding surface theory that has been successfully encoded into the ABAQUS. Based on the proposed numerical model, the development of soil arching and accumulative deformation in a piled embankment subjected to train loading is investigated. The load transfer mechanism and deformation characteristics of a piled embankment in terms of the embankment height, velocity of the train, pile spacing and wheel static load are analyzed. The research results can provide some reference for the design of piled embankments under train loading. [ABSTRACT FROM AUTHOR]

Measured loads in centrifuge tests on piled embankments were compared with values calculated by three analytical arching models. The Zaeske and Van Eekelen models use sets of arches that give the direction of the load transfer, and result in an increasing load on the soft soil with increasing embankment thickness or surcharge load, which matches the measurements. The Svanø model, however, assumes that the load on the soft soil remains constant with increasing embankment thickness or surcharge load, thereby being transferred directly to the piles. Therefore, the Zaeske andVan Eekelen modelsmatch themeasurements better than the Svanømodel. TheVan Eekelen model slightly overestimates the pile efficiency for relatively thin embankments, but matches the measurements better than the Zaeske model for increasing embankment thickness or surcharge load. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Zhejiang University: Science A is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Full-scale tests were performed on embankments with a beam foundation supported by floating and end-bearing piles. An analytical model based on the soil arching mechanism appeared to be able to predict accurately the vertical load transferred to a group of beams at a small center-to-center distance. However, when the distance between the beams was too wide or the embankment was too low to mobilize soil arching, the vertical load transferred to a beam could be predicted accurately with a model based on the punching shear mechanism. Greater embankment loads could be transferred to a piled beam through soil arching than could be transferred through punching shear. Beams in a piled embankment should be placed sufficiently close to each other to allow application of the soil arching model for design. Embankment loads could be transferred to both floating and end-bearing piles. Although load-transfer behavior was similar, the settlement of floating piles was significantly larger than the settlement of end-bearing piles. Settlement in a piled embankment could be reduced considerably by the application of end-bearing piles with a group of beams at a small center-to-center distance. [ABSTRACT FROM AUTHOR]

Abstract: The stability analysis of a piled embankment under seismic loading is considered, with a special emphasis on the optimization of the reinforcement layout by splitting the initial group of vertical piles into two symmetrically inclined arrays of parallel inclusions. The bidirectionally-reinforced soil thus obtained is appropriately described, at the macroscopic scale, by a three-phase model, conceived as an extension of the two-phase model previously developed for unidirectionally-reinforced soils. The model is implemented in a finite element formulation and related numerical code, which is used for simulating the behavior of the piled embankment up to failure. The results of these simulations, which favourably compare with upper bound yield design calculations, clearly indicate that the seismic resistance of the embankment can be considerably increased from symmetrically inclining the piles, even without taking the potential benefits of their flexural resistance into account. [Copyright &y& Elsevier]

This paper presents a probabilistic analysis of a geosynthetics-reinforced and pile-supported (GRPS) embankment by using reliability, sensitivity and uncertainty propagation techniques. Compared to the traditional deterministic evaluation methods, the analyses performed in this work allow designers to rationally consider the uncertainties of material properties and quantify their influences on the embankment performance. Additionally, complementary information/results could be obtained which enables an informed design decision for engineers. This feature is further enhanced in the paper by proposing a new analysis procedure in which four carefully selected probabilistic techniques are combined with an efficient deterministic model. The contribution of the proposed procedure lies in providing a variety of valuable results (e.g., failure probability and sensitivity index) related to the GRPS embankment performance but with a limited computational time. An application of the procedure is presented in the paper. The obtained results revealed that the studied GRPS embankments have relatively low failure probabilities considering a usual traffic loading but could be risky under extreme loading conditions. Based on the sensitivity analysis, all the random parameters are ranked according to their quantified importance. Some discussions are also provided, trying to link the procedure with practical designs and to explain the uncertainty modeling with more details. [ABSTRACT FROM AUTHOR]

• Subsoil provides a substantial support and reduces the reinforcement tension. • Design guideline CUR226 and standard EBGEO agree well with the numerical results. • 3D Numerical discrete analysis and comparison with analytical models. Three-dimensional numerical analyses using the discrete element method are conducted to investigate several fundamental aspects related to soil-structure interaction and mobilization mechanisms in the geosynthetic-reinforced and pile-supported embankments. The contributions of the soil arching, tensioned membrane effect, friction interaction, subsoil support, and punching failure are investigated. The results indicated that the inclusion of the geosynthetic enhances the stress transfer from the subsoil to piles due to the tensioned membrane action, and the stress distribution is more uniform as compared to piled embankment without geosynthetic. However, the tension distribution in geosynthetic is not uniform and the maximum tension occurs near the pile edge. Numerical results also proved that the subsoil provides substantial support and reduces the reinforcement tension while shear stresses are mobilized along the upper and lower sides of soil-geosynthetic interfaces. These mechanisms should be considered in theoretical models to produce a more realistic approach. Finally, ten available design methods are reviewed and compared to the numerical results to assess the performance of analytical models. The results showed that the design method of Pham, CUR 226 design guideline, and EBGEO design standard agree well with the numerical results and are generally better than the results of all other methods. [ABSTRACT FROM AUTHOR]

A geosynthetic-reinforced pile-supported (GRPS) embankment is a complex soil-structure system. The response of a GRPS system is affected by the interactions among its five linked elements, namely the geosynthetic (a synthetic product used in civil engineering to stabilise the terrain), foundation, granular platform, fill soil, and geological media underlying and surrounding the foundation. The key load transfer mechanism in a GPRS embankment is a combination of various phenomena that include arching in the fill layers, tensioned membrane effect of the geosynthetic, frictional interaction, and support of the soft subsoil. Referring to the current numerical and experimental studies, a new theory has been developed in this study by combining the arching theory for the soil layer and the tensioned membrane theory for the geosynthetic. The subsoil effect with both linear and non-linear models and the frictional interaction are also included in the proposed method, thereby providing a more comprehensive design approach than the earlier methods that considered only either the tensioned membrane theory or the arching theory. It is demonstrated in this work that the proposed method produces results that are in good agreement with the experimental observations. [ABSTRACT FROM AUTHOR]