Study On Reinforcement Effect Of Geocell-Aeolian Sand Subgrade Under Traffic Load

Based on the dynamic triaxial test of geocell reinforcement of aeolian sand and the field test of the Aurian Desert expressway,this thesis studies the dynamic performance of geocell and the reinforcement effect of geocell on aeolian sand subgrade under traffic load.The influence of different dynamic stress amplitude,confining pressure and geocell on the dynamic strength of aeolian sand and the cumulative plastic strain model of aeolian sand reinforced by geocell were studied by triaxial test.The variation trend of the time history curve and frequency domain curve of dynamic stress,dynamic velocity and dynamic acceleration under different working conditions and the vibration attenuation law along the depth and horizontal direction were studied through the field experiment of geniture-reinforced aeolian sand.According to the vibration attenuation curve,the calculation method of subgrade working area depth and the replacement ratio of aeolian sand roadbed instead of gravel soil roadbed reinforced by geocell is determined.The specific research results are as follows:(1)The axial cumulative strain curves of aeolian sand and geocell are similar.When the soil is subjected to dynamic load,the strain rate of the soil in the early loading stage is relatively large.The dynamic strain occurs,the soil is damaged,the strain rate decreases,and the deformation becomes stable.The total plastic strain decreases with the increase of confining pressure.When the dynamic stress amplitude increases,the cumulative strain of soil increases correspondingly,and the cumulative strain curve changes gradually from stable type to creep type and finally to failure type.The cumulative plastic strain of soil decreases with the increase of loading rate or dynamic load frequency.(2)The increase of dynamic stress on the top surface of the eolian sand roadbed presents a linear increase in a load of accompanying vehicles,and the increase of accompanying vehicle speed presents a linear decrease,and the influence of vehicle axle load is greater than the speed.Aeolian sand subgrade’s longitudinal attenuation of dynamic stress is an exponential function.The vertical attenuation coefficient of dynamic stress in geocell-aeolian sand is much greater than that in gravel soil,and the effect of vehicle speed on dynamic stress attenuation is little.The subgrade working depth calculating method is determined according to the dynamic stress attenuation curve and dead stress line.(3)The vibration period of the geocell-reinforced aeolian sand side is slightly larger than that of the gravel soil side;The vibration frequency distribution of the test vehicle is mainly within 30 Hz,and gradually decreases with the increase of the test vehicle’s driving speed.Compared with gravel soil,the vibration amplitude on one side of geocells decreases slowly but smoothly.From the Angle of main frequency amplitude analysis,the vertical attenuation ratio of the main frequency amplitude of aeolian sand reinforced by geocell is 2.66 times that of gravel soil under different test speeds.From the Angle of vibration energy attenuation,the equivalent amplitude vertical attenuation ratio of aeolian sand reinforced by geocell at different test speeds is 1.29 times that of gravel soil on average.The working depth of the embankment with vibration velocity on the side of eolian sand reinforced by geocell is all less than that on the side of gravel soil,and the maximum difference can reach 0.55 m.(4)By combining field tests and theoretical analysis,the influence process and law of dynamic load on the dynamic acceleration of aeolian sand roadbed reinforced by geocell are studied.The results show that the vibration response caused by the test vehicle is concentrated within 30 Hz,and the higher the vibration frequency,the faster the vertical attenuation in the road structure.The vibration attenuation of aeolian sand reinforced by geocell is better than that of gravel soil.The replacement ratio of geocell reinforced aeolian sand roadbed to gravel roadbed ranges from 0.31 to 0.42.The results can provide a reference for the design of the desert expressway subgrade.