The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Yan Zhuang - One of the best experts on this subject based on the ideXlab platform.
-
a simple design approach to analyse the Piled Embankment including tensile reinforcement and subsoil contributions
Geotextiles and Geomembranes, 2021Co-Authors: Yan Zhuang, Kang Yu Wang, Xiaoyan Cui, Jun ZhangAbstract:Abstract There is not one generally accepted approach for the design of geogrid-reinforced pile-supported (GRPS) Embankments. Relevant mechanisms include arching of the Embankment material, but also the effect of geogrid reinforcement and potentially a contribution from the underlying subsoil. This paper presents a simple design approach to identify the contribution of all three mechanisms, in which the contribution of multi-layered geogrid reinforcement is also presented. To validate the theoretical predictions for the effect of geogrid reinforcement and the potential contribution of underlying subsoil, a series of three-dimensional finite element analyses are conducted. It is found that a point of ‘maximum arching’ is increased with the height of Embankment. This study also presents that the reinforcement could reduce the ultimate stress on the subsoil. However, this requires significant sag of the reinforcement. It is found that the sag of reinforcement is very sensitive to the span of the reinforcement between piles, but relatively insensitive to the stiffness of the reinforcement. For a case with three layers of geogrid, the upper two grids carry relatively little tension compared to the bottom layer. This in turn leads to an approximate but simple equation of vertical equilibrium which may be of use in design.
-
an analytical method to calculate the settlement of reinforced Piled Embankment considering three dimensional deformed geogrid
European Journal of Environmental and Civil Engineering, 2020Co-Authors: Xiaoyan Cui, Yan Zhuang, Shuai Ning, Kang Yu WangAbstract:The methods available to predict the strain and tension of geogrid are regularly based on two-dimensional condition, however, the three-dimensional deformed shape of geogrid is seldom considered in...
-
the load transfer mechanism in reinforced Piled Embankment under cyclic loading and unloading
European Journal of Environmental and Civil Engineering, 2020Co-Authors: Yan Zhuang, Xiaoyan Cui, Sheng Zhang, Guoliang Dai, Xueliang ZhaoAbstract:The load transfer mechanism is complicated and closely concerned with the control of settlement in Geogrid-reinforced and pile-supported (GRPS) Embankments. However, the research on load transfer m...
-
Finite element analysis on the dynamic behavior of soil arching effect in Piled Embankment
Transportation Geotechnics, 2018Co-Authors: Yan Zhuang, Kang Yu WangAbstract:Abstract Most research conducted so far has investigated the soil arching in Piled Embankment under static loads, knowledge on their dynamic behaviors under transient loads of moving vehicles is rather limited in the literature, especially considering the subsoil consolidation, and therefore it deserves more research attention. This paper presented a series of finite element (FE) models to investigate the dynamic behavior of soil arching effect in Piled Embankment. At a given load cycle number of 300, since the subsoil was not fully consolidated, ‘Model B’ yielded much smaller results in terms of both the settlement and earth pressure coefficient than ‘Model A’, with the difference of approximately 50%. A three-dimensional (3D) column model with a simplified subsoil consolidation procedure (Model E) was presented to simplify the problem of time-consuming and difficult to convergence. A close agreement was observed between the two models both in terms of the settlement and the earth pressure coefficient of the Embankment, and therefore concluded that ‘Model E’ was much more suitable for the simulation of Piled Embankment under dynamic loads. The parametric study relating to the dynamic load type, velocity and vehicle wheel load showed that the soil arching effect remained valid, but was reduced under dynamic loads, especially when the vehicle wheel load and velocity were relatively large. The dynamic load type was found to have an obvious influence on the soil arching effect, in which the settlement increased by approximately 6% when varying the half-sine load type to the sine load type. As expected, the increased vehicle wheel load and velocity aggravated the dynamic vertical stress and settlement of the Piled Embankment.
-
case studies of reinforced Piled high speed railway Embankment over soft soils
International Journal of Geomechanics, 2016Co-Authors: Yan Zhuang, Xiaoyan CuiAbstract:AbstractSoil arching in the reinforced Piled Embankment is investigated in this paper on the basis of two case studies of high-speed railways constructed in the eastern coastal region of China. The majority of the overburden load was found to have been transferred from the soil to the pile because of soil arching in the Piled Embankment. In addition, the critical height was approximately 2.6–3.8 times the net pile spacing. The adapted Terzaghi method, the BS8006 method, the Hewlett and Randolph method, EBGEO, and a simplified analytical method used to analyze the reinforced Piled Embankment were discussed and verified by the two cases. It was found that the adapted Terzaghi method was consistent with the measurement for the stress reduction ratio, with an error of 2.0–38.0%. The simplified analytical method predicted the maximum geogrid strain with the error of 6.7–33.2%, and assessed the maximum settlement at the subsoil surface with an error of 4.4–51.0%.
Daniel Dias - One of the best experts on this subject based on the ideXlab platform.
-
geosynthetic reinforced Piled Embankment modeling using discrete and continuum approaches
Geotextiles and Geomembranes, 2021Co-Authors: Quoc Anh Tran, Daniel Dias, Pascal VillardAbstract:Abstract Understanding the load transfer mechanism can support engineers having more economical design of geosynthetic reinforced Piled Embankments. This study aims to investigate the load transfer mechanisms by two different numerical methods including the Discrete Element Method (DEM) and the Finite Difference Method (FDM). The DEM model adopts (a) discrete particles to simulate the micro-structure of the granular materials and (b) coupled discrete element – finite element method (DEM-FEM) to capture the interaction between granular materials and geotextiles. On the other hand, the FDM model uses an advanced constitutive soil model considering the hardening and softening behaviour of the granular materials. The numerical results show that the geotextiles can only contribute to the vertical loading resistance in cases where the soils between piles are soft enough. In terms of design, an optimum value of the geotextile tensile stiffness can be found considering the load, the soft soil stiffness and the thickness of the Embankment. Both the DEM and the FDM show that a high geotextile tensile stiffness is not required since an extra stiffness will slightly contribute to the efficiency of the geosynthetic reinforced Piled Embankments. Nevertheless, both models are useful to optimize the design of geosynthetic reinforced Piled Embankments.
-
Geosynthetic reinforcement on pile-supported Embankment
Geosynthetics International, 2018Co-Authors: Romain Girout, Matthieu Blanc, Luc Thorel, Daniel DiasAbstract:Rigid piles are used to reinforce soft soil foundations and thus increase Embankment stability. This technique is improved by placing one or more geosynthetic reinforcement (GR) layers inside or at the base of the Embankment. A series of 33 small scale models were tested using a geotechnical centrifuge. Soft soil settlement was imposed by the downward displacement of a tray. First, a series of models were prepared to examine how the load transmitted to the pile network increased with the Embankment thickness. Using the same configuration, two identical models were prepared to successively test two different types of GR (geosynthetic reinforcement). Another approach was used to study how the external surcharges applied on the Embankment affect load transfer. The results showed that, compared to the Piled Embankment, the load transfer increased for the case of the geosyntheticreinforced pile-supported Embankment (GRPSE) due to the membrane effect. The membrane effect is higher when the GR is stiff and its vertical distance from the pile is reduced. Numerical modelling reveals that, when another GR layer is added, the second GR has an effect only if punching is sufficient. However, the second layer did not reduce Embankment settlement.
-
Experimental and numerical studies for geosynthetics anchorage with wrap around
HAL CCSD, 2016Co-Authors: Lajevardi, Seyed Hamid, Pascal Villard, Silvani Claire, Briançon Laurent, Daniel DiasAbstract:International audienceThe soil reinforcement by geosynthetic is widely used in civil engineering structures: reinforced slopes and walls, Embankments on compressible and soft soils, slope on a stable foundation, Embankments on cavities and retaining structures, reinforcement in the base layers of railroads and road constructions, bridging over sinkholes or reinforced abutments, Piled Embankment, reinforced foundation mattresses.The stability of these structures specially depends on the efficiency of the anchors holding the geosynthetic sheets. The anchorages simple run-out and with wrap around are two most commonly used approaches. Designing the required dimensions of the anchorage with wrap around remains problematic. In order to improve the available knowledge of the anchorage systems behaviour, the experimental and numerical studies were performed jointly. This paper focuses on the physical and numerical models of the geosynthetics behaviour in two anchors (simple run-out and with wrap around). Laboratory pull-out tests, performed with two experimental tanks under controlled conditions, consisted in the pull-out of three reinforced non-woven needle-punched geotextiles (uinaxial or biaxial with different stiffness) anchored following various geometries in different kind of soil.In order to confirm and to complete the experimental studies presented in these anchorage systems, a two-dimensional discrete-element model (DEM) was performed. The advantage of the numerical model is its ability to reproduce the behaviour of the geosynthetic and the soil/geosynthetic interaction. The parameters deduced from physical model are used in this numerical study
-
Piled Embankment on soft soil reinforced with geosynthetic
2014Co-Authors: Romain Girout, Matthieu Blanc, Luc Thorel, Daniel DiasAbstract:The technique of soft soil improvement by rigid inclusions allows the transfer of the load applied at the mattress top towards the piles by two mechanisms: arching in the granular mattress and membrane tensioning if a geosynthetic has been included in the mattress. A parametric study has been carried out to understand the role of the thickness of the mattress on the load transfer and the differential settlements. The experimental results obtained on centrifuge models have been compared with the “Recommendations for Design and Analysis of earth Structures using Geosynthetic Reinforcements” and finite element modelling.
-
three dimensional numerical modeling of a Piled Embankment
International Journal of Geomechanics, 2009Co-Authors: Orianne Jenck, Daniel Dias, Richard KastnerAbstract:This paper proposes a three-dimensional numerical modeling of an Embankment over a soft ground mass improved by vertical stiff piles, using a finite-difference continuum approach (FLAC3D). Arching occurs in the Embankment granular material, leading to load transfer onto the piles and surface settlement reduction and homogenization. The Embankment, the piles, and the soft ground are explicitly taken into account in the proposed numerical model. First, a unit cell from the pile grid is considered. Two sorts of soft clay deposits and two Embankment materials are successively modeled. The soft soil behavior is simulated by the modified Cam Clay model and the Embankment material behavior is successively simulated by an elastic perfectly plastic model with a Mohr–Coulomb failure criterion and then by an isotropic hardening elastoplastic model, the CJS2 model, in order to approach the real system behavior. The calculations are performed in drained conditions, simulating the long-term behavior. The impact of the ...
Kang Yu Wang - One of the best experts on this subject based on the ideXlab platform.
-
soil arching of Piled Embankment in equal settlement pattern a discrete element analysis
Symmetry, 2021Co-Authors: Kang Yu Wang, Jun Cao, Xinquan Wang, Yingjie NingAbstract:Soil arching, which occurs in the Piled Embankments, plays an important role in stress redistribution between the relatively soft subsoil and the stiffer piles. The formation of the soil arching depends on the differential settlement of the Embankment fill above the pile and the subsoil. The soil arching effect is barely investigated in the literature from the perspective of differential settlement of piles and soils. Based on the discrete element method (DEM), this paper develops a classic trapdoor test model to investigate the differential settlement in Piled Embankment during the downward movement of the trapdoor, and to explore the formation mechanism of soil arching in equal settlement pattern by changing the width of the pile cap and the height of the Embankment. Due to symmetry, only one section of the laboratory test model is simulated herein. It was found that the soil arching formed under the equal settlement pattern remained unchanged after a certain degree of development, and the height of the equal settlement did not change at 0.7(s-a), where s is the pile spacing, and a is the width of the pile cap. The height of the Embankment (H) and the width of the pile cap (a) have a significant influence on the formation of the equal settlement pattern when the width of the trapdoor is kept constant. Both the decrease in “H” and the increase in “a” facilitate the differential settlement of the soil between the piles and the pile-soil, enabling the slip surface to develop upward gradually, thereby hindering the formation of the equal settlement pattern.
-
a simple design approach to analyse the Piled Embankment including tensile reinforcement and subsoil contributions
Geotextiles and Geomembranes, 2021Co-Authors: Yan Zhuang, Kang Yu Wang, Xiaoyan Cui, Jun ZhangAbstract:Abstract There is not one generally accepted approach for the design of geogrid-reinforced pile-supported (GRPS) Embankments. Relevant mechanisms include arching of the Embankment material, but also the effect of geogrid reinforcement and potentially a contribution from the underlying subsoil. This paper presents a simple design approach to identify the contribution of all three mechanisms, in which the contribution of multi-layered geogrid reinforcement is also presented. To validate the theoretical predictions for the effect of geogrid reinforcement and the potential contribution of underlying subsoil, a series of three-dimensional finite element analyses are conducted. It is found that a point of ‘maximum arching’ is increased with the height of Embankment. This study also presents that the reinforcement could reduce the ultimate stress on the subsoil. However, this requires significant sag of the reinforcement. It is found that the sag of reinforcement is very sensitive to the span of the reinforcement between piles, but relatively insensitive to the stiffness of the reinforcement. For a case with three layers of geogrid, the upper two grids carry relatively little tension compared to the bottom layer. This in turn leads to an approximate but simple equation of vertical equilibrium which may be of use in design.
-
an analytical method to calculate the settlement of reinforced Piled Embankment considering three dimensional deformed geogrid
European Journal of Environmental and Civil Engineering, 2020Co-Authors: Xiaoyan Cui, Yan Zhuang, Shuai Ning, Kang Yu WangAbstract:The methods available to predict the strain and tension of geogrid are regularly based on two-dimensional condition, however, the three-dimensional deformed shape of geogrid is seldom considered in...
-
Finite element analysis on the dynamic behavior of soil arching effect in Piled Embankment
Transportation Geotechnics, 2018Co-Authors: Yan Zhuang, Kang Yu WangAbstract:Abstract Most research conducted so far has investigated the soil arching in Piled Embankment under static loads, knowledge on their dynamic behaviors under transient loads of moving vehicles is rather limited in the literature, especially considering the subsoil consolidation, and therefore it deserves more research attention. This paper presented a series of finite element (FE) models to investigate the dynamic behavior of soil arching effect in Piled Embankment. At a given load cycle number of 300, since the subsoil was not fully consolidated, ‘Model B’ yielded much smaller results in terms of both the settlement and earth pressure coefficient than ‘Model A’, with the difference of approximately 50%. A three-dimensional (3D) column model with a simplified subsoil consolidation procedure (Model E) was presented to simplify the problem of time-consuming and difficult to convergence. A close agreement was observed between the two models both in terms of the settlement and the earth pressure coefficient of the Embankment, and therefore concluded that ‘Model E’ was much more suitable for the simulation of Piled Embankment under dynamic loads. The parametric study relating to the dynamic load type, velocity and vehicle wheel load showed that the soil arching effect remained valid, but was reduced under dynamic loads, especially when the vehicle wheel load and velocity were relatively large. The dynamic load type was found to have an obvious influence on the soil arching effect, in which the settlement increased by approximately 6% when varying the half-sine load type to the sine load type. As expected, the increased vehicle wheel load and velocity aggravated the dynamic vertical stress and settlement of the Piled Embankment.
-
a simplified model to analyze the reinforced Piled Embankments
Geotextiles and Geomembranes, 2014Co-Authors: Yan Zhuang, Kang Yu Wang, Hanlong LiuAbstract:Abstract It is an economic way to use the Piled Embankment for the construction of Embankment over soft soil. The combination of piles and reinforcement can effectively reduce the differential settlement at the surface of Embankment. The paper presents a simplified model for analysis of an Embankment of granular fill on soft ground supported by reinforcement and piles. This model is based on consideration of the arching effect in granular material proposed by Hewlett & Randolph. The vertical equilibrium of the unit body at the center of pile caps immediately below the reinforcement is established. The refinements of the model are that the failure mechanisms of the arch both at the crown and at the pile cap were considered, three-dimensional situation was taken into account for reinforced Piled Embankment, calculation of the vertical stress carried by the subsoil due to arching effect and reinforcement for multi-layered soil was proposed. Using the simplified model, the influence of Embankment height, one-dimensional compression modulus of subsoil, tensile stiffness of reinforcement on stress reduction ratio (SRR) and tensile force of reinforcement is investigated. It is found that the model can be used to assess the relative contribution of the reinforcement and subsoil. The results show that subsoil gives a major contribution to overall vertical equilibrium, while the reinforcement gives obvious contribution at relatively large settlement. The inclusion of the reinforcement can reduce the vertical stress acting on the subsoil. The simplified model is then evaluated by three case studies. The results of this model show good consistence with these cases.
Y. Zhuang - One of the best experts on this subject based on the ideXlab platform.
-
finite element analysis of a Piled Embankment with reinforcement and subsoil
Geotechnique, 2016Co-Authors: Y. Zhuang, E. A. EllisAbstract:In 2014, the authors of this paper considered predictions of reinforcement tension in a Piled Embankment from British standard BS 8006 published in 2010 and the 2012 amended version, and compared the results with finite-element model predictions. In keeping with BS 8006, any contribution from the subsoil beneath the Embankment was ignored. The present paper extends that earlier work by also considering the potentially beneficial contribution of a lightly overconsolidated clay subsoil layer, both in the finite-element predictions and as a simple modification to the BS 8006 predictive method. It is assumed that there is no ‘working platform’ (granular) material below the pile cap level, and that the water table in the subsoil does not drop, since either of these factors would be likely to significantly reduce the ability of the subsoil to carry load from the Embankment. As anticipated, the subsoil support reduces reinforcement tension. When compared to the finite-element results the proposed modified BS 800...
-
three dimensional behavior of biaxial geogrid in a Piled Embankment numerical investigation
Canadian Geotechnical Journal, 2015Co-Authors: Y. Zhuang, K Y WangAbstract:Biaxial geogrid in current research is oversimplified, and the three-dimensional orthotropic nature of the biaxial geogrid has not been fully understood in numerical investigations. A comparative s...
-
finite element analysis of a Piled Embankment with reinforcement compared with bs 8006 predictions
Geotechnique, 2014Co-Authors: Y. Zhuang, E. A. EllisAbstract:The British ‘Code of practice for strengthened/reinforced soils and other fills' (BS 8006) was substantially revised in 2010, with a further ‘Corrigendum' in 2012. Historically, BS 8006 considered arching in a Piled Embankment, based on an interpretation of the ‘Marston' equation. The 2010 revision included an alternative method related to the analysis of arching in a Piled Embankment, which was proposed by Hewlett and Randolph in 1988, and later itself amended in the 2012 Corrigendum. This contribution considers BS 8006 predictions of reinforcement tension using these methods as a basis for Embankment load on the reinforcement, for a wide range of Piled Embankment geometries. The predictions are compared with results from three-dimensional finite-element analysis, demonstrating encouraging correspondence with the Hewlett and Randolph approach (but noting that the 2010 revision overpredicts the data whereas the 2012 revision underpredicts it). Good predictions of maximum reinforcement sag are also achieve...
-
three dimensional finite element analysis of arching in a Piled Embankment
Geotechnique, 2012Co-Authors: Y. Zhuang, E. A. EllisAbstract:Piled Embankments rely upon arching of the Embankment material onto underlying piles, thus potentially significantly reducing load on the soft subsoil that more generally prevails beneath the Embankment. Finite-element modelling of a Piled Embankment in plane strain has previously been reported; the ‘subsoil' was not explicitly modelled, but was represented by a vertical stress acting on the underside of the Embankment. This technical note considers extension of this work to three dimensions. The results make particular reference to prediction of the stress on the subsoil at the point of ‘maximum arching' and the height of influence of arching within the Embankment.
-
Plane strain FE analysis of arching in a Piled Embankment
Proceedings of the Institution of Civil Engineers - Ground Improvement, 2010Co-Authors: Y. Zhuang, E. A. Ellis, Hai-sui YuAbstract:The results of a series of linearly elastic-perfectly plastic plane strain finite-element (FE) analyses are reported, investigating the arching of a granular Embankment supported by pile caps over a soft subsoil. The objective of the research was to contribute further to generic understanding of arching in a Piled Embankment, and the contribution of tensile reinforcement near the base of the Embankment. The stress state in the Embankment and load on the subsoil were examined. The analyses demonstrate that the ratio of the Embankment height to the centre-to-centre pile spacing is a key parameter in determining the behaviour. The potential contribution of tensile reinforcement near the base of the Embankment was also considered. It was found that arching in the Embankment occurred at relatively small settlement of the underlying subsoil, whereas much more settlement was required for sag of the reinforcement to have significant effect in further reducing the stress on the subsoil.
S J M Van Eekelen - One of the best experts on this subject based on the ideXlab platform.
-
basal reinforced Piled Embankments
2015Co-Authors: S J M Van EekelenAbstract:A basal reinforced Piled Embankment consists of a reinforced Embankment on a pile foundation. The reinforcement consists of one or more horizontal layers of geosynthetic reinforcement (GR) installed at the base of the Embankment. The design of the GR is the subject of this thesis. A basal reinforced Piled Embankment can be used for the construction of a road or a railway when a traditional construction method would require too much construction time, affect vulnerable objects nearby or give too much residual settlement, making frequent maintenance necessary. The GR strain needs to be calculated to design the GR. Multiplying this GR strain by the GR stiffness gives the tensile force, which needs to be smaller than the long-term GR tensile strength. The GR strain is calculated in two steps. Calculation step 1 divides the load – the weight of the Embankment fill, road construction and traffic load – into two load parts. One part (load part A) is transferred to the piles directly. This part is relatively large because a load tends to be transferred to the stiffer parts of a construction. This mechanism is known as ‘arching’. The second, residual load part (B+C) rests on the GR (B) and the underlying subsoil (C). Calculation step 2 determines the GR strain on the basis of the result of step 1. Only the GR strips between each pair of adjacent piles are considered: they are loaded by B+C and may or may not be supported by the subsoil. The GR strain can be calculated if the distribution of load part B+C on the GR strip, the amount of subsoil support and the GR stiffness are known. An implicit result of this calculation step is the further division of load part B+C into parts B and C. Several methods for the GR design are available, all with their own models for calculation steps 1 and 2. The methods give results that differ immensely. The Dutch CUR226 (2010) and the German EBGEO (2010) adopted Zaeske’s method (2001). However, measurements that were published later (Van Duijnen et al., 2010; Van Eekelen et al., 2015a) showed that this method could be calculating much higher GR strains than those measured in practice, leading to heavier and more expensive designs than necessary. The objective of the present study was to establish a clearer picture of load distribution in a basal reinforced Piled Embankment and, on that basis, to develop and validate an analytical design model for the geosynthetic reinforcement in a Piled Embankment. The results were described in five papers published in the international scientific journal ‘Geotextiles and Geomembranes’. Those journal papers can be found in Chapters 2, 3, 4, 5 and Appendix A of this thesis (Van Eekelen et al., 2012a, 2012b, 2013, 2015a and 2011 respectively). Chapter 2 presents a series of twelve 3D experiments that were carried out at the Deltares laboratory. The scaled model tests were carried out under high surcharge loads to achieve stress situations comparable with those in practice. A unique feature of these tests was that load parts A, B and C could be measured separately, making it possible to compare the measurements with calculation steps 1 and 2 separately. In these tests (static load, laboratory scale), smooth relationships were obtained between the net load on the fill (surcharge load minus subsoil support) and several measured parameters such as load distribution and deformation. Consolidation of the subsoil resulted in an increase in arching (more A) and more tensile force in the GR (more B and more GR strain). The measured response to consolidation depends on the fill’s friction angle. A higher friction angle results in more arching during consolidation. One of the major conclusions based on the test series was that the load on a GR strip is approximately distributed as an inverse triangle, with the lowest pressure in the centre and higher pressure close to the piles. This conclusion was the basis for the remainder of this doctorate study and the development of the new calculation model. Chapter 3 considers calculation step 2. This chapter starts by comparing the measurements in the experiments with the calculation results of step 2 of the Zaeske (2001) model, which uses a triangular load distribution on the GR strip and considers the support of the subsoil underneath the GR strip only. It was found that Zaeske’s model calculates GR strains that are larger than the measured GR strains (approximately a factor of two for GR strains larger than 1%). Chapter 3 continues with the suggestion of two modifications to Zaeske’s step 2. Firstly, the load distribution is changed from a triangular to an inverse triangular load distribution. Secondly, the subsoil support is extended from the support by the subsoil underneath the GR strip to the subsoil underneath the entire GR between the piles. The new step 2 model with these modifications produces a much better fit with field measurements than Zaeske’s model. Chapter 4 considers calculation step 1, the arching. Additional tests were conducted for this purpose, varying factors such as the fill height. This chapter gives an overview of the existing arching models and introduces a new model. This Concentric Arches model (CA model) is an adaptation and extension of the models of Hewlett and Randolph (1988), and Zaeske (2001), which have been adopted in several European design guidelines. Some countries use Piled Embankments without GR. Introducing GR changes the load distribution considerably. A major part of the load is then exerted on the piles and the residual load is mainly exerted on the GR strips between the piles, with the load being distributed approximately as an inverse triangle. Chapter 4 explains the development of the load distribution as a result of continuing GR deflection; new small arches grow within the older larger ones. Smaller arches exert less load on their subsurface. This idea is related to the concentric arches of the new model, which gives an almost perfect description of the observed load distribution in the limit state situation. Furthermore, the new model describes the influence of the fill strength and Embankment height correctly. Chapter 5 compares the existing, and the newly introduced, design models with measurements from seven full-scale projects and four series of scaled model experiments. Two of these seven field projects were conducted in the Netherlands and they were carried out in part for this doctorate research. One of the four experimental series – the one presented in Chapters 2 and 4 – was conducted specifically for the present research. The other measurements were reported earlier in the literature. The calculations were carried out using mean, best-guess values for the material properties. The calculation results from the CA model match the measurements much better than the results of the arching models of Hewlett and Randolph (1988), and of Zaeske (2001). The results of the CA model are also the closest match with the results of the 3D numerical calculations, as described in Van der Peet and Van Eekelen (2014). These authors also show that the new CA model responds better to changes in the fill friction angle than any of the other models considered. When there is no subsoil support, or almost no subsoil support, the inverse triangular load distribution on the GR strips between adjacent piles gives the best match with the measurements. When there is significant subsoil support, the load distribution is approximately uniform. This difference between the situation with or without subsoil support is understandable when one considers that most load is attracted to the construction parts that move least. In the cases with limited subsoil support, the load distribution that gives the minimum GR strain should be used to find the best match with the measurements. The GR strain calculated with Zaeske’s model is on average 2.46 times the measured GR strain. The GR strain calculated with the new model is on average 1.06 times the measured GR strain. The calculated GR strain is therefore almost a perfect match with the measured GR strain. The new Dutch CUR226 (2015) has therefore adopted the model proposed in this thesis.
-
validation of analytical models for the design of basal reinforced Piled Embankments
Geotextiles and Geomembranes, 2015Co-Authors: S J M Van Eekelen, Adam Bezuijen, Af Van TolAbstract:Van Eekelen et al., 2012a, Van Eekelen et al., 2012b and Van Eekelen et al., 2013) have introduced an analytical model for the design of the geosynthetic reinforcement (GR) in a Piled Embankment. This paper further validates this model with measurements from seven full-scale tests and four series of scaled model experiments. Most of these measurements have been reported earlier in the literature. The new model describes arching with the “Concentric Arching model” (CA model). This model is an extension of the single arch model of Hewlett and Randolph (1988) and the multi-scale model of Zaeske (2001), which is also described in Kempfert et al. (2004). For load-deflection behaviour, Van Eekelen et al., 2012a, Van Eekelen et al., 2012b and Van Eekelen et al., 2013) proposed the use of a net load distribution that is inverse triangular instead of uniform or triangular. These authors also proposed the inclusion of all the subsoil support beneath the GR in the calculations. On the basis of comparisons between the measurements and calculations, it is concluded that the CA model matches the measurements better than the models of Zaeske or Hewlett and Randolph. Where there is no subsoil support, or almost no subsoil support, the inverse triangular load distribution on the GR strips between adjacent piles gives the best match with the measurements. Cases with subsoil support generally lead to less GR strain. In the cases with significant subsoil support, the load distribution is approximately uniform. In the cases with limited subsoil support, it should be determined which load distribution gives the minimum GR strain to find the best match with the measurements.
-
Axial pile forces in Piled Embankments, field measurements
'Thomas Telford Ltd.', 2015Co-Authors: S J M Van Eekelen, Bezuijen Adam, Af Van TolAbstract:Several measurements were carried out in a basal reinforced Piled Embankment in the Netherlands. The present paper focuses on the influence of truck passages on the axial forces in the piles. The changes in axial forces in the piles were measured using two systems: (1) optic fibres attached to a square steel tube pile, measuring pile strains at ten positions along the pile length and (2) the total pressure on the pile cap with total pressure cells. Additionally, the axle loads of passing trucks and the load on the subsoil between the piles were measured. The measured changes in pile strains show that most truck load is transported to the subsoil by friction along the pile shafts. Comparison between measurements and calculations show that the truck wheel loads are spread stronger than assumed by Boussinesq
-
european analytical calculations compared with a full scale brazilian Piled Embankment
10th International conference on geosynthetics Proceedings, 2014Co-Authors: S J M Van Eekelen, Mss Almeida, Adam BezuijenAbstract:Measurements have been carried out in a full-scale Brazilian basal reinforced Piled Embankment. The subsoil beneath the geosynthetic reinforcement (GR) had been excavated before the installation of the reinforced Embankment. The Embankment was relatively thin in comparison to the pile cap spacing, resulting in relative much load on the GR. GR strains and settlements have been measured making it possible to validate analytical models. Many analytical design models for the design of Piled Embankments distinguish two calculation steps; calculation step 1; the arching and calculation step 2 ; the load deflection behaviour of the GR. This papser presents the comparison of the full-scale test with a new step 1 - model ; the Concentric arches model (Van Eekelen et al. 2013) and several step 2 models. The new concentric arches model is an extension on the models of Hewlet and Randolph (1988) and Zaeske (2001) and takes into account the 3D nature of the arching. The new model was developed because experiments had showed a load distribution on the GR in a Piled Embankment that could not be explained with the existing models. The new model does explain the measured load distribution.
-
basal reinforced Piled Embankments validation of inverse triangular load distribution with an extended terzaghi equation
10th International conference on geosynthetics (IGS - 2014), 2014Co-Authors: Adam Bezuijen, S J M Van EekelenAbstract:The friction model developed by Terzaghi is used to calculate the vertical stress on the geosynthetic reinforcement (GR) in a 2D Piled Embankment. The model developed is based on Terzaghi's (1943) calculation of the stresses in a trapdoor experiment. In the present paper, it is assumed that the deformation of a geosynthetic reinforcement should not be simulated with one trapdoor, but with a series of trapdoors. For a 2D situation this results in an inverse triangular load distribution on the GR. This has also been found in experiments. The results show that the GR itself has a significant influence on the load distribution and experiments without GR should not be used to develop calculation models for the situation with GR.