Study On Pre-punched Structure Design And Mechanical Performance Control Of Industrial PP Geogrid

The plastic geogrid is a product obtained by processing a polymer sheet by a"high temperature stretching-room temperature cooling"process.It has the advantages of low cost,light weight,high strength,corrosion resistance,etc.,so it is widely used in the foundation of various buildings,and plays a role in strengthening and stabilizing the soil.The two-way geogrid is most widely used.However,the longitudinal and transverse tensile strengths of the two-way geogrid are inconsistent,which causes"wasting"of the mechanical properties of the material.Domestic and foreign scholars have studied the interaction between geogrid and soil,but the research on geogrid production process is less,which makes the production lack of certain theoretical guidance,and also restricts the development of new geogrids.Therefore,this paper explores the basic mechanical properties of industrial PP materials,and optimizes the pre-punching structure of the two-way geogrid,which provides some theoretical guidance for the development of new geogrids.Firstly,this paper explores the basic mechanical properties of industrial PP based on the previous studies.The high temperature tensile test was used to investigate the influence of various main process parameters(tensile temperature,tensile speed,tensile displacement,heating time and sheet thickness)on the geometrical dimensions of the specimen and the tensile stress and strain at high temperature.The experiment obtained the influence of each main process parameter on the basic mechanical properties of the material.Secondly,the pre-punching structure of the two-way geogrid is optimized.The tensile strength,nominal elongation and performance utilization coeflficient of the two-way geogrid were investigated by the difference of the span ratio and the longitudinal and lateral spacing.The influences of the span ratio and the vertical and horizontal spacing difference on the mechanical properties of the two-way geogrid are obtained,and the geogrid with uniform longitudinal and transverse tensile strength is obtained.Then,the Marlow model in the finite element analysis software ABAQUS was used as the constitutive model of the industrial PP material,and the dumbbell-shaped spline was subjected to stretch forming simulation.The geometry and stress strain of the simulated sample were compared with the test to verify the accuracy and reliability of the simulation.On this basis,the two-way grid under different conditions is simulated and analyzed,the geogrid molding process is obtained,and the stress and strain distribution inside the grid is revealed.Finally,the development of multi-directional geogrid was briefly explored,and the forming process of two kinds of four-way geogrid(X-shaped structure and small diamond-shaped structure)was simulated by ABAQUS.Based on the research of different pre-punching schemes,the Similar Forming Method for the pre-punching structure design of multi-directional geogrid is proposed.The pre-punching structure of the small-diameter four-way geogrid is designed by using this method,after the simulation,the distribution of ribs' size,stress and strain are relatively uniform.