Load Transfer Mechanisms And Design Method Of Low Geosynthetic-reinforced Embankment(LGR)Subjected To Localized Voids

The low geosynthetic-reinforced(LGR)embankment is constructed inevitably over areas that present a high risk of sinkholes,where the granular or cohesive materials are used above the geosynthetic to minimize the financial and environmental costs.The sinkholes beneath or close to embankments may lead to disruptions of road infrastructures caused by the vehicle load and underground water.Traffic accident or road damage is reduced or prevented by horizontal reinforcement solutions generally.This kind of applications is commonly used in some countries,but the shortage of this solution is in the definition of the appropriate design for LGR embankment because the physical mechanisms are not yet fully understood.In this paper,some works were carried out and some innovative achievements were made to solve the existing shortages.1.Previous research achievements is insufficient on the load transfer mechanisms,delayed deformation and collapse,three-dimensional analysis,bearing capacity and failure modes of the geosynthetic embankments subjected to localized voids by summing up some researches,then present the key points on load mechanisms and exiting design methods.A set of recommendations and insights for further research were summarized to provide references for the LGR embankment-above-voids system.2.To investigates the bearing capacity characteristics and failure modes of the LGR embankment-above-voids system by using large deformation finite element analysis and normalization method.Six distinct failure modes of the entire system are found:trapdoor,sidewall,combination of roof and sidewall,rotational roof,combination of roof and single sidewall and slope failure mode.Five types of slip lines of LGR embankment are then summarized,such as vertical,trapezoid,double-cambered,partial-vaulted and vaulted slip lines.This study also presents the effects of influencing parameters(e.g.,rupture strength of reinforcement,location and size of void,height and shear strength parameters of embankment fills)on the ultimate bearing capacity of the system.Design charts are obtained to determine the required soil properties and to evaluate the bearing capacity characteristics of the system.3.Through some shallow trapdoor tests,it is summarized that the shapes of the slip lines of the shallow trapdoor is turritus under plane strain conditions.Analytical solutions in terms of coefficient of lateral stress and vertical stresses for the any depth of the shallow foundation under the action of partially developed soil arching effect was deduced,which is based on the major principle stress rotation and the differential settlement of soil layers.The influence of main parameters of partially developed soil arching effect was investigated.The results reveal that the larger depth-width ratio and the displacements-width ratio of trapdoor are needed to develop the arch fully.In addition,the vertical stresses of the fills increases with the increase in the effective internal friction angles and angles of slip lines.4.Through analyzing the stress-strain relations of the platform,the design method considered the principal stress rotation due to differential settlements is improved and optimized under the assumption that there is a parabolic overload distribution perpendicular to the sheet overlying the void.The design method of the tensile stiffness of geosynthetic reinforced sheet and the embankment height based on load transfer mechanisms of LGR embankment spanning sinkholes is proposed.The solutions in terms of surface subsidences can be applied to the serviceability limit state deign and ultimate one simultaneously.The accuracy and rationality of the method are verified by comparisons of the current design methods to provide a reference for such structures.