Study On Load Transfer Mechanism Of Piled Reinforced Embankments

Piled Reinforced Embankment is a new type of soft soil foundation treatment technology,which has been widely used in engineering practices. However, there is not relevant design specification at home. Besides,load transfering mechanism of Piled Reinforced Embankments is very complex, which is no unified conclusion at home and abroad.For example, the soil arching,the bearing load by geotextile and the load distribution form upper the geotextile, the bearing load by soft soil between piles and the load distribution form upper the soft soil,which are not yet clear. Therefore,it is very important to study on load transfering mechanism of Piled Reinforced Embankments for theoretical significance and engineering application value.Firstly,this article expounds soil arching and geotextile reinforcement effect on Piled Reinforced Embankments. Secondly,this paper compares Piled Reinforced Embankments with piled-reinforeced earth composite fondation by using PL AXIS. Finally, six influencing factors were evaluated to study critical height of filling soil, soil arch,the tension and deformation of geotextile, and stress distribution forms on the surface,which includes pile spacing, the internal friction angle of filling soil, fill height, confining compression modulus of soft soil,the elastic modulus of pile, and the tensile stiffness of geotextile. And then,based on soil arch theory, the results calculated by FORTRAN and MATLAB are analyzed with the results of field test or numerical simulation.This paper gets the following conclusions:1.Relative to piled-reinforeced earth composite fondation. Piled Reinforced Embankments’ piles bearing load is bigger, whose embankment vertical settlement is smaller and well-distributed. However, stress concentration phenomenon is more obvious at the pile cap edges,and the thickness of mattress layer should be increased.2,Critical height raises along with the decrease of confining compression modulus of soft soil between piles or increase of pile spacing.However, the internal friction angle of filling soil, the elastic modulus of pile, and the tensile stiffness of geotextile don’t influence critical height. As compared with the existing theoretical model, critical height of Kempfertet aL,Carsslon,Hewlett and Terzaghi’ s modles reduces in turn at the sameconditions.3.Pile efficiency raises along with the incease of internal friction angle of filling soil and fill height or decrease of pile spacing and confining compression modulus of soft soil between piles.However, the tensile stiffness of geotextile is without effect.4.As compared with the existing theoretical model, the value of Low, Hewlett and Chen Yun-min’s theory model about pile efficiency reduces in turn at the same conditions. However,difference of pile efficiency about Low et al.,Hewlett, and Chen Yun-min’s theory models reduces along with the incease of internal friction angle of filling soil and fill height or decrease of pile spacing.5.The maximum of geotextile tension always appears in the pile cap edge.However,geotextile tension raises along with incease of filling height and the tensile stiffness of geotextile,and reduces along with the incease of internal friction angle of filling soil and confining compression modulus of soft soil.Besides, geotextile tension increase along with pile spacing in a certain range.6.The vertical deformation of geotextile raises along with incease of filling height,pile spacing or decrease of confining compression modulus of soft soil.However^geotextile deformation is not related to internal friction angle of filling soil or tensile stiffness of geotextile.7.At the same vertical plane of geotextile, the normal stress and shear stress acting upper the geotextile surface is similar to that under the geotextile surface, which may be the reseaon why geotextile tension is so small.Normal stress distribution at geotextile’s fluctuation surface is uniform, rather than a triangle or inverted triangular distribution.Soft soil’s ground reaction force between piles is evenly distributed.8.From results of Taijin Highway K18+183?K18+309 test section,it,s known Zaeske variable curvature arch model,Van Eekelen concentric arch model or Hewlett dome arch model can be as theory basis of designing pile reinforced embankment.