Research On Mechanical Properties Of Asphalt Pavement With Graded Granular Base Reinforced By Geocell

Thermal cracking and drying shrinkage crack on semi-rigid base materials are inevitable,as result of the reflection crack appear on asphalt pavement due to the stresses on the top of the crack which leads to more and more damaged roads.Gravel base has a lot of advantages like better heat preservation and drainage property,better adaptability for roadbed inhomogeneous deformation.However,its disadvantage is obviously limited its application with larger plastic deformation and smaller carrying capacity than semi-rigid base.It is inevitable that the semi-rigid base will be replaced by graded gravel base due to the roads developmental requirement to keep the health and performance of asphalt pavement.It is the important aspect to invest in the future as following:increase the bearing capacity and decrease the plastic deformation of graded gravel while keeping its advantage..First,the basic research about the clayey soil,physical property and modulus of graded gravel is used in the foundation.The strengthening mechanism of geocell used for strengthening the padding is analyzed in this step.Results show that the bearing capacity of the graded gravel base can be increased by limiting the lateral displacement of the padding which is helpful to reduce the reflection crack on asphalt pavement.Then,the indoor test model is established to analysis on the effect of geocell welding distance,height,gravel gradation,subgrade modulus,load for geocell reinforcement graded gravel base structure,which were related to deformation modulus,elastic modulus and plastic deformation.The research results show that geocell can effectively improve the geocell reinforcement graded gravel base bearing capacity and deformation restoring capacity,and can make the deformation modulus,elastic modulus significantly improve,can greatly reduce plastic deformation.Changing geocell welding distance can obtain the largest increase up to 27.73%on the deformation modulus and the largest increase up to 12.03%on elastic modulus.Continuous gradation gravel can obtain the largest increase up to 28.71%on deformation modulus and the largest increase up to 13.59%on elastic modulus than discontinuous gradation.With subgrade modulus larger,geocell reinforcement effect is better.The single layer modulus reinforced by 150-300 and 200-500 geocell with the continuous graded gravel base are 1.57 and 1.85 times than without strengthening.Subsequently,through the establishment of finite element model,the response characteristics of the stress and strain of the geocell reinforcement graded gravel asphalt pavement structure under vehicle load are researched,and a comparative study on graded gravel base structure and semi-rigid base structure is made.The research results show that the geocell can effectively limits in the lateral displacement of the load of graded grave,effectively improve the strength of the graded gravel base,significantly reduce asphalt pavement surface layer tensile stress and tensile strain,and the shear force is better than semi-rigid base,improving the pavement structure flexural tensile fatigue performance.However,the stress and strain of the semi-rigid base have a substantial increase,which reflects the unique characteristics of the graded grave base reinforced by geocel.Last,finite element analysis on the influences of geocell welding distance,height,modulus and sub-layer modulus,which were related to stress and strain response characteristics of each asphalt pavement layer.The research results show that increasing height,proper welding distance,increasing modulus can improve surface layer stress and strain in different extent,but have a little effect on surface layer maximum shear,road surface deflection and sink,subgrade surface pressure and the whole pavement structure strength.