Study On The Interfacial Property And Node Enhancement Mechanism Of Buckle-node Interlocking Geogrid

As a kind of reinforced material with unique mesh structure,geogrid has been widely used in soft foundation treatment,reinforced embankment,reinforced retaining wall,repairing slope and high-rise soil reinforcement.The interaction between the geogrid and the earth is the key to improve the strength of reinforced soil structure.However,the interface characteristics between the geogrid and the soil are affected by many factors,which directly determines the deformation and stability of the reinforced soil structure.Through investigation and study,it is found that the main factors leading to the failure of reinforced soil structure are the shortage of material properties and structural forms of traditional geogrid,such as the fracture of longitudinal and transverse ribs,the peeling failure of nodes and the insufficient surface roughness.Therefore,based on the analysis of the traditional geogrid reinforcement effect and damage characteristics,this paper developed a buckle-node interlocking geogrid with high strength and high friction characteristics.The main research contents and conclusions of this paper include the following aspects:(1)Laboratory tensile test and node peeling test were carried out in sequence for the longitudinal and transverse ribs and the buckled nodes of the buckle-node interlocking geogrid.The results show that both longitudinal and transverse ribs and nodes have high strength,and the appearance of many filamentous fiber bundles on the surface of ribs is a sign of impending fracture.The buckled nodes are mainly plastic damage,with high peel strength and can provide additional strength to the ribs.(2)The influence of vertical stress,compaction degree and node form on the interface characteristics of reinforced soil was studied by using self-developed large-scale pull-out tester with buckle-node interlocking geogrid as reinforcement material and clay as test filler.The motion of soil disturbed by geogrid is measured by using attitude angle sensor,and the mechanism of interaction between reinforcement and soil during drawing is analyzed.The results show that the increase of vertical stress and compaction can effectively increase the frictional resistance of the interface and the deformation of the geogrid,but the disturbance degree of the reinforced soil interface is reduced.The geogrid near the clamping end deforms the most and gradually attenuates along its buried length.Under the same vertical stress and compactness,compared with square buckled nodes,I-shaped buckled nodes have stronger interaction between reinforcement and soil,which is the preferred form of geogrid nodes.(3)On the basis of the pulling test,the limit equilibrium state of the soil under the action of buckled nodes is analyzed theoretically,and the limit analysis theory of the Meyerhof foundation is revised.In the aspect of test,the strengthening mechanism of the node form to the reinforced soil interface was analyzed by setting a control group.The results show that,under the same vertical stress,the contribution rate of I-shaped buckled nodes to the interface friction resistance of reinforced soil is greater than that of the square buckled nodes.However,as the vertical stress increases step by step,the difference of contribution rate between the two types of buckled nodes is gradually narrowed.The two types of buckled nodes attached to the longitudinal ribs can effectively increase the interface strength of the reinforced soil and improve the interface characteristics of the reinforced soil,but the I-shaped grilles have more advantages in improving the interface characteristics of the reinforced soil.(4)A method of reinforcing the interface of reinforced soil with horizontal interlayer formed by the soil mass near the replacement filling geogrid is proposed,and the interlayer structure parameters(filler particle size,gradation distribution,interlayer thickness,etc.)are studied by laboratory drawing test.The results show that under the same vertical stress,compared with the single graded gravel interlayer,the continuous graded gravel interlayer has a more significant effect on improving the interaction between geogrid and soil,but the content of fine aggregate should be controlled reasonably.There is an optimum value for the interlayer thickness.In engineering applications,pulling test should be carried out to verify the optimal engineering properties of interlayer fillings,so as to maximize the frictional characteristics of the interface between geogrid and soil.