The Tensile Property And Technology Research Of Plastic Geogrid

Plastic geogrid is a material mainly applied in civil engineering. It is widely used in road construction, soft foundation reinforcement, stiffener bracing and other projects due to its superior properties like good fatigue and aging resistence, high tensile strength, as well as long-term creep resistance. With the extensive use and considerable production, however, domestic plastic geogrid production lack systematic theotical guidane. In practical production, in order to get the best production process, not only some properties of the geogrid such as its tensile strength and elongation, but also the final appearance, the difficulty of the production process control and the cost of the production must be considered. Therefore, research work on the production process of plastic geogrid has important significance.In the present thesis, experiments and finite element simulation were conducted to study the production factors which will influence the final performance of plastic geogrids. Also, the mechanism of these factors was analyzed and summarized.For the uniaxial tensile process of the plastic geogrids, the effects of hole spacing, size, and shape, as well as the sheet thickness on the tensile properties of geogrid were studied based on single variable experiments and orthogonal experiments. The results show that these four factors have different effects on the performance of geogrid, and they have a great impact on the tensile strength, along with some forming quality such as neck-rate.For the biaxial tension process of the plastic geogrids, the effects of hole spacing and size on the two-directional tensile properties of geogrid were studied by single variable method. The results show that with the same stretching length, speed and temperature, there are some difference between the properties of the twice tensile geogrids along the tensile direction, and the hole spacing and size also have different influence on the two-dimensional tensile geogrids. Besides, the ratio of hole spacing and diameter influences the tensile performance and appearance quality of geogrids. Thus, the production process can be improved by controlling the value of the ratio.Finally, simulation analyses of the uniaxial and biaxial forming process of the plastic geogrids were conducted using finite element simulation. Under the conditions of different hole spacing, hole sizes, hole shape and sheet thicknesses, the distribution laws of the stress and strain, and the change of cross-sectional area during the tensile process of the geogrids were analyzed. Specific effects of various factors on the performance of geogrid were interpreted and illustrated.