Study On Dynamic Characteristics Of Reinforced Foundation Of Coastal Highway

Compared with the general highway foundation,the coastal highway foundation has its special characteristics.There are a lot of soft soil in the coastal area,the soft soil has the characteristics of high water content,low density,high liquid limit,high compressibility and high sensitivity,it performances badly on the engineering property.Traffic load is a kind of cyclic dynamic load,the highway built on the soft soil foundation is easy to produce large deformation and settlement under the long-term action of traffic load.It is an effective method to deal with the highway soft soil foundation by using the technology of the reinforced soil,which not only can enhance the overall stability of the roadbed,but also reduce the uneven settlement of the road.At present,the research and design of highway in the country and abroad are mostly concentrated on the static load,and there is little research about the stress characteristics and deformation of highway under the action of dynamic load,however,the research on the dynamic characteristics of reinforced soft soil foundation under cyclic loading is less,and the theoretical level is far behind the engineering practice.This paper takes Qingdao coastal highway silt soft soil foundation as the research object,the elastic modulus and damping ratio as the research content of soft soil under cyclic loads,studies on dynamic characteristics of reinforced soft soil foundation.Through the finite element software to simulate and analyze the deformation and settlement characteristics of the embankment under the action of dynamic load.These studies can provide a better theoretical basis for the design of highway and the application of the reinforcement technology in the highway engineering of soft soil foundation.The main contents and conclusions of this paper are as follows:(1)Through indoor soil test,Qingdao coastal area soft soil has the engineering characteristics of high water content,high void ratio,high compressibility,low shear strength characteristics,belonging to the typical Quaternary soft soil.(2)The dynamic triaxial test was carried out on the soft soil samples under different confining pressures(50,100,150KPa)and different reinforcement.The results show that the dynamic elastic modulus of the soft soil samples with the same consolidationconfining pressure is decreased with the increase of the dynamic strain,and the dynamic damping ratio increases with the increase of the dynamic strain.The dynamic elastic modulus of soft soil samples with different reinforcement conditions increases with the increase of confining pressure,while the dynamic damping ratio decreases with the increase of confining pressure.(3)The results show that the dynamic elastic modulus and dynamic damping ratio of the soft soil can be improved by the method of sand cushion and reinforcement,when adding two layers of reinforcement,the effect of the reinforcement material is not fully exerted,and the effect is not much improved.So in the engineering,the actual reinforcement layer should be determined according to the engineering conditions.(4)Through the ABAQUS finite element software to simulate and calculate the deformation and settlement of the soft foundation embankment under four different reinforcement schemes.The results show: just laying sand cushion at the junction of embankment and soft soil foundation has a small effect on the settlement and lateral displacement control;after laying a layer of geotechnical grid and sand cushion,the vertical settlement of the embankment and the lateral deformation of the embankment can be obviously reduced.If the thickness of sand cushion is not large,only increase the number of layers,the effect of reinforcement is not obvious.(5)By using two layers of geotechnical grid and sand cushion method,the whole settlement and uneven settlement of pavement under traffic load can be significantly reduced.So as to ensure the overall stability of the embankment and road safety.