Study On The Action Mechanism Of Geocell Reinforcement In High Fill Retaining Wall Subgrade

Due to the increasing prevalence of natural conditions such as topography and hydrology and the phenomenon of "heavy traffic",the design difficulty and strength requirements of new highways are higher than those of the past,so a series of new subgrade structures have been derived,one of which is the retaining structure combined with geocell and retaining wall subgrade.The reinforced-soil is an effective method to improve the performance of subgrade.As the best of many reinforcing materials,the effect or mechanism of geocell in high-filling retaining wall subgrade is still unclear.In order to comprehensively understand the engineering benefits of geocell and various parameters in retaining wall subgrade,recognize its failure mode and provide theoretical support for the related design,this subject systematically studies it through the following steps:(1)Strictly referring to the similar theory,the indoor model test is carried out with the field scheme as the prototype and the reinforcement spacing as the working condition distinction.The bearing performance of retaining wall subgrade and the mechanical characteristics of geocell and retaining wall with different reinforcement spacing are studied.The test results show that: the bearing performance and initial modulus of the subgrade are significantly increased by the implantation of geocell,which is negatively correlated with the reinforcement spacing;the tensile stress of the reinforcement in the first layer increases much faster with the loading than of the remaining layers;the extreme value of the stress on the retaining wall is located at the monitoring point 0.22 H,indicating that the reinforcement has little effect on the internal friction angle of the fill.(2)Three-dimensional large-dimensional model is established through ABAQUS for extend research.The calculation takes different geocell heights,geocell modulus and internal friction angle of the fill as variables to study the effects of the above parameters on the deformation characteristics of the pavement and retaining wall.The calculation results show that the improvement of displacement is gradually weakened with the increase of modulus,and the control effect of displacement of retaining wall is significant when the modulus is greater than 50Mpa;the reinforcing effect is the best when the geocell height is 20 cm;30～35° is a more reasonable interval of internal friction angle of filler.(3)Based on the strength reduction method,the failure modes before and after reinforcement are compared and analyzed.Then five groups of important parameters in the project are set as the characteristic sequence,and the safety coefficient is taken as the parent sequence.Finally,the sensitivity analysis of the parameters is carried out by using grey correlation analysis.The calculation results show that the implantation of geocell makes the plastic strain and range of subgrade under the same reduction factor smaller,the formation process of its shear zone is relatively slow,and the projected length of slip surface is larger than that of unreinforced subgrade,indicating that reinforcement slows down the failure process.Within the range of calculated parameters,the factors affecting the stability of subgrade are ranked as follows: geocell height>cohesion>internal friction angle>number or spacing of geocell reinforcement layers>soil modulus.(4)In order to optimize the reinforcement scheme of the retaining wall subgrade,the tensile stress law of the geocell in the three-dimensional calculation is summarized.Based on this law,three reinforcement schemes are designed for calculation and comparative analysis.The results show that the tensile stress distribution and increasing rate of the geocell are similar to the test results.The tensile stress of the geocell of layer 2-5 are 64%,35%,21% and 13% of the first layer.Compared with the traditional equally spaced reinforcement,the solution of concentrating the reinforcement in the shallow layer can save up to 37.5% of the reinforcing material with similar reinforcement effect.The proposed equally spaced reinforcement scheme also has 25% effect and its reinforcement of the road subgrade is more comprehensive.